2014 Chemistry Calendar

The quintessential Chemistry Calendar for 2014 is now available.

You can download your free calendar at

http://www.ausetute.com.au/downloads.html

Happy New Year !

Extrapolation and Interpolation

AUS-e-TUTE has just added a new tutorial, game and test to help you learn how to make predictions using graphs.
Using our new resources, you will have no trouble explaining and using the terms interpolation and extrapolation!

Writing Lab Reports

AUS-e-TUTE has just added new resources to help you write lab reports.
You will find new tutorials, games and tests for each of the following:
1. Writing Lab Reports (an overview)
2. Accuracy and Precision
3. Experimental Errors (random vs systematic)
4. Variables (dependent vs independent)
5. Potting points on a graph

Just log-in in the Members Only Test Centre to see all these new resources.

Teachers will also find a new resource, wizard that generates a pre-test for stoichiometry.
The results of the pre-test will help teachers identify the students that need help with simple algebra, or with reading and interpreting algebraic questions, before you plow on into stoichiometry.

Just log-in in the Teachers area to see all this new resource.

Argon Hydride in Space

Almost 1,000 years ago, the Chinese recorded a bright new object in the night sky. This is believed to be a star that exploded. The remnant of that exploded star is now called the Crab Nebula and it is about 6,500 light years from Earth.
Europe launched its Herschel Space Observatory in 2009, and in 2012 Astronomers used it to study the emission lines from Crab Nebula. What the scientists found were 2 bright emission lines from an area of shining dust. It was only by consulting databases of the known properties of different molecules that the scientists could finally identify these emission lines as coming from a very special molecule, argon hydride.
Argon hydride is special because it is the first time that molecules of a Noble Gas (Group 18) element have been found in space. On Earth, the naturally occurring Noble Gas (Group 18) elements are monatomic gases. Atoms of Noble Gas elements have a full valence shell of electrons so they tend not to react with other atoms.
Something really interesting must be happening in the Crab Nebula for argon hydride to be formed naturally. The researchers believe that the argon formed when the original star exploded. The intense energy of the explosion stripped electrons off the argon atoms, ionising them. Ionised argon atoms then reacted with hydrogen molecules to form argon hydride molecules.

Reference
M. J. Barlow, B. M. Swinyard, P. J. Owen, J. Cernicharo, H. L. Gomez, R. J. Ivison, O. Krause, T. L. Lim, M. Matsuura, S. Miller, G. Olofsson, E. T. Polehampton. Detection of a Noble Gas Molecular Ion, 36ArH , in the Crab Nebula. Science, 2013; 342 (6164): 1343 DOI: 10.1126/science.1243582

Further Reading
http://ausetute.com.au/trendec.html
http://ausetute.com.au/trendie.html
http://ausetute.com.au/massconv.html
http://ausetute.com.au/members/emissions.html

Suggested Study Questions:

1. 1 light year is approximately 9.5 x 10¹⁵ metres. How far from Earth is the Crab Nebula in kilometres?
2. 1 astronomic unit (1 AU) is approximately 1.5 x 10¹¹ metres. What is the distance between Earth and the Crab Nebula in astronomic units?
3. What sort of instrument can be used to observe the emission lines of hot gases?
4. Explain how these emission lines are produced.
5. Give the electron configuration of an atom of argon.
6. With reference to the electron configuration of argon, explain why compounds of argon are not found naturally on Earth.
7. Write an equation to show the loss of an electron from a gaseous argon atom.
8. Explain how the hydride ion can be formed from a hydrogen atom.
9. Give a likely molecular formula for a molecule of argon hydride.
10. Is argon hydride most likely to an ionic compound or a covalent compound? Explain your answer.

Excel : Line of Best Fit

You can easily use Microsoft Excel to find the equation for the line of best fit for experimental data points.

Remember that the equation of a straight line is y = mx + b
where m is the slope (gradient) of the line and b is the intercept on the y axis (that is, when x =0).

Microsoft excel will calculate both the slope of the line, m, and the y-intercept, b, for you.

First you will need to open up a new excel spreadsheet and set up your data.
Here we have used Row 1 of columns A and B for our headings (x values and y values).
Various values for x and y have then been entered into the cells: 

cell	A	B
1	x values	y values
2	1.02	11.0
3	2.05	21.3
4	2.96	31.2
5	4.12	39.7
6	4.86	53.4

Next, we highlight any two adjacent cells (empty cells) somewhere else in the same spreadsheet, for example A8 and B8

cell	A	B
1	x values	y values
2	1.02	11.0
3	2.05	21.3
4	2.96	31.2
5	4.12	39.7
6	4.86	53.4
7
8

Next to the fx symbol above the cell headings A, B, etc, type in =LINEST(B2:B6, A2:A6)
 then press Ctrl+Shift+Enter simultaneously.
(B2 is the first  y value to be used in the calculation and B6 is the last y value to be used in the calculation. Similarly, A2 is the first of the x values to be used in the calculation and A6 is the last of the x values to be used in the calculation.)
Your spreadsheet should now look this:

cell	A	B
1	x values	y values
2	1.02	11.0
3	2.05	21.3
4	2.96	31.2
5	4.12	39.7
6	4.86	53.4
7
8	10.50606	-0.21918

The number in cell A8 is the slope (m) of the line of best fit.
The number in cell B8 is the y-intercept (b) of the line of best fit, that is, the point with coordinates (0,b)
The equation for the line of best fit for this data is y = 10.50606x -0.21918

In order to draw the line of best fit for the experimental data above, we only need to calculate new values for y using the equation for the line of best fit (that is, the first and last points on the line of best fit).:
given x=1.02 ,then,  y = (10.50606 x 1.02) -0.21918 = 10.5
and x=4.86 , then, y =(10.50606 x 4.86) -0.21918 = 50.8

cell	A	B	C
1	x values	y values	new y values
2	1.02	11.0	10.5
3	2.05	21.3
4	2.96	31.2
5	4.12	39.7
6	4.86	53.4	50.8
7
8	10.50606	-0.21918

Plot the points (1.02, 10.5) and (4.86, 50.8) on the graph of experimental data and draw a straight line between these two points. This is the line of best fit for the experimental data in the table.

Further Activities:
Go to http://www.ausetute.com.au/members/bestfitline.html

1/ Enter the data above into the tool for calculating the two points needed to draw a line of best fit. Check the new y values above, and see what the graph looks like.

Graph the data points in questions 2 to 5 below and draw the line of best fit:

2/ (0.23, 9.75), (0.94, 6.39), (1.77, 5.73), (4.59, 4.91), (11.52, 0.33)
3/

time / min	mass / g
0	102.8
2	73.4
4	48.7
6	27.3
8	10.9

4/

volume / mL	5.0	10.0	15.0	20.0	25.0
mass / g	3.2	7.1	9.4	13.5	14.8

5/ At time 0, the temperature of a reaction mixture was 25^oC. The temperature of the reaction mixture was then recorded every minute for 4 minutes. The results of the experiment were temperatures of 29^oC, 32^oC, 35^oC and 40 ^oC.

CGS and the Solvay Process

Coal seam gas (CSG) is any naturally occurring gas, such as methane, that is trapped in underground coal seams by water and pressure. Methane, often called natural gas, is a commercially valuable resource, so mining companies drill into the coal seam, pump the water out, which releases the pressure and forces the gases to the surface. Queensland is believed to have about 98% of Australia's coal seam gas reserve. More than 4,000 CSG wells in Queensland account for about 17% of that state's electricity. NSW has about 500 CSG wells.

The water that is produced in coal seam gas mining is not suitable for human consumption. The water is most often very salty and can contain heavy metals and toxic compounds.
A new drilling project in the Pilliga Forest in the north-west of NSW is expected to produce an average of 3 tonnes of salt a day over three years!

(http://www.smh.com.au/environment/coal-seam-gas-industry-faces-salt-overload-20131204-2yqx8.html#ixzz2mYw2aSQc)

That's a lot of salt! Left to itself, lying around near the mine, it will poison land and waterways. So what can you do with all this salt?

Salt, sodium chloride, is an important commercial chemical. It is used to produce chlorine and sodium hydroxide, and is used in other industrial process, it is used directly for snow and ice control, as a mineral in animal diets, as a preservative, as a flavouring agent, and as a reagent for water softening. The total (deliberate) production of sodium chloride world-wide is about 250 million tonnes per year.

One way to get rid of the salt produced in coal seam gas mining is to turn it into something else, sodium carbonate for instance.
In Australia, the Penrice Soda Products company in Osborne, South Australia, operates a plant using the Solvay Process to turn sodium chloride into sodium carbonate.
The overall chemical equation for the Solvay Process is
CaCO₃(s)   +   2NaCl (aq)      Na₂CO₃(aq)   +   CaCl₂(aq)
 CaCO₃(s) is present in limestone and the NaCl is the by-product of the CGS mining.
The company currently produces about 325,000 tonnes of sodium carbonate every year.

Further Reading:
density
yield

Solvay Process

Suggested Study Questions:

1. How much NaCl will the Pilliga Forest mining project produce in one year?
2. Assume that there are 4,500 CSG mines in Australia and they each produce 3 tonnes of salt a day. How much salt will be produced in one year in Australia from CSG mines?
3. The density of sodium chloride is about 2.2 g/cm³. Calculate the volume of salt produced each day by the Pilliga Forest CSG mine.
4. Assume a single truck can carry 100 tonnes of salt. How many truck loads of salt will be produced at the Pilliga Forest CSG mine each year?
5. Give one environmental issue that would be raised in trucking salt over large distances. Explain how the problem could be reduced.
6. Give one commercial problem associated with trucking salt over large distance using the same truck. Explain how the problem could be reduced.
7. What is the maximum amount, in tonnes, of sodium carbonate that could be produced using 1 truck load of sodium chloride?
8. What is the maximum amount, in tonnes, of calcium carbonate required to completely convert 1 tonne of sodium chloride to  sodium carbonate?
9. If the actual yield of sodium carbonate is 86.2%, what mass of sodium carbonate would be produced from the complete reaction of 1 tonne of sodium chloride?
10. Assuming the solvay process was used to convert all the salt from all Australia's CSG mines into sodium carbonate, how much sodium carbonate would be be produced?
11. World production of sodium carbonate is currently about 42 million tonnes per year. If Australia began production of sodium carbonate using all the salt produced in the CSG mines, what percentage increase would there be in world production of sodium carbonate?
12. What would you suggest Australia do with the salt produced as a by-product of coal seam gas mining?

Ice Calorimeter

Scientists began studying the heat produced in chemical reactions long before they even understood what a chemical reaction was!
At a time when scientists still believed that matter was made up of elements like Aristotle's earth, air, fire and water, and the concept of energy had not yet been formulated, they were using the newly invented
mercury-in-glass thermometer to measure the temperature of substances and the results were surprising.

The December 2013 edition of AUS-e-NEWS discusses the development of the very first calorimeter, the ice calorimeter, in 1780.

AUS-e-NEWS is AUS-e-TUTE's FREE quarterly newsletter.

If you would like to subscribe to AUS-e-NEWS, please email 

and type subscribe as the subject of the email.

Drawing the Line of Best Fit

You've got a table of experimental data.
You've plotted the data on a graph.
Now, how do you draw a line of best fit?
Why should you draw a line of best?

AUS-e-TUTE has just added new resources that answers these questions and helps you draw the line of best for your data by giving you a tool to use which makes the whole process as easy as clicking a button!

Visit http://www.ausetute.com.au and click on the Line of Best Fit link.

Salts of Drugs a Health Risk

Many studies have shown that excess salt is harmful to heart health, but many commonly prescribed medicines have sodium added to improve their absorption into the body, but the effect of doing this has not been known. For example, 1 Alka-Seltzer tablet contains 324 mg of aspirin (the drug) and 445 mg of sodium.
University of Dundee and College of London researchers have found that a person taking the maximum, daily dose of some medicines would exceed the recommended daily dietary intake limits for sodium. In Australia, the total maximum recommended limit of sodium for adults should be less than 2300 mg per day (less for children). The label on the Alka-Seltzer tablets carries a warning that you should not take more than 8 tablets per day.
In the study, the researchers found that patients taking the sodium-containing medication had a 16% increased risk of a heart attack, were 7 times more likely to develop high blood pressure, and, were 28% more likely to die, compared with patients who took the non-sodium containing versions of the same drug.

So why do we add sodium to drugs if it is potentially harmful?

We do this because many drugs are actually insoluble in water. The cells in your body are made up mostly of water, so if you want to be able to transport a drug around the body, and have it absorbed into cells, it is beneficial if the drug is soluble in water.

How do we add sodium to drugs?

If the drug is, for example, a weak acid like aspirin, then it is not very soluble in water.
Being a weak acid, though, aspirin can undergo a proton transfer (neutralisation) reaction with a base such as sodium hydroxide. The product of a neutralisation reaction are salt and water.
acid + base → salt + water

aspirin + sodium hydroxide → sodium salt of aspirin + water

The sodium salt of aspirin readily dissolves in water by dissociating into positive sodium ions and negative "aspirin" ions.


Reference:
BMJ-British Medical Journal (2013, November 26). High salt levels in medicines increase risk of cardiovascular events. ScienceDaily. Retrieved November 28, 2013, from http://www.sciencedaily.com­ /releases/2013/11/131126191557.htm 

Further Reading
aspirin
mass conversions 
ppm
molarity
neutralisation
proton transfer reactions
acid dissociation constants

Suggested Study Questions: 

1. Convert these masses in milligrams to masses in grams
• 324 mg
• 445 mg
2. The label on the Alka-Seltzer packet recommends dissolving 2 tablets in water. For these two tablets, calculate the mass in milligrams of
• aspirin
• sodium
3. If you were to take the maximum number of tablets, 8, in a day, how much of each of the following substances would you be ingesting?
• aspirin
• sodium
4. Would you be exceeding the recommended daily dietary intake limits for sodium in Australia? Explain your answer.
5. A low salt food is one that contains less than 120 mg of sodium per 100 g of food. If Alka-Seltzer were to be considered a low salt food, what would the mass of each tablet need to be?
6. Aspirin has the molecular formula C₉H₈O₄. What is the molar mass of aspirin?
7. The sodium salt of aspirin has the molecular formula C₉H₇O₄^-Na⁺. What is the molar mass of the sodium salt of aspirin?
8. Calculate the mass of sodium in 1 Alka-Seltzer tablet due to the sodium salt of aspirin.
9. Compare the mass of sodium calculated above to the actual mass of sodium present in 1 Alka-Seltzer tablet according to the package. How would you explain the difference in the two masses?
10. If a person dissolved 2 Akla-Seltzer tablets in 150 mL of water, what is the concentration of sodium ions in the water in
    • mol/L
    • mg/L
    • ppm
11. Recommendations for the daily intake of potassium are higher than those for sodium at 4700 mg day, so one way to alleviate the sodium problem in aspirin tablets might be to replace the sodium with potassium. Describe one way that you could produce the potassium salt of aspirin.

 

Structure of Benzene

AUS-e-TUTE has just uploaded new resources for the Benzene topic.
You will find the new Structure of Benzene tutorial, game and test under the Aromatic Compound heading when you log-in to the Test Centre.
Relevant syllabus study guides have also been updated to include these new links.
The key concepts can be found in the "free-to-view" tutorial at
http://www.ausetute.com.au/benzene.html
There is a clickable link on that benzene page which will take AUS-e-TUTE members straight to the complete new tutorial.

Pthalate in Plastics

Researchers in the USA have found a link between premature births and the exposure of  pregnant women to a group of organic (carbon based) chemicals known as phthalates.

Phthalates have been used for more than 50 years as plasticizers, substances which are added to plastics to increase their flexibility, transparency, durability and longevity. For example, adding phthalates to polyvinyl chloride (PVC) makes the PVC soft and flexible, ideal for flexible plastic tubing. You will find phthalates in many products you come into contact with every day, from vinyl upholstery and floor tiles, to plastic food containers and wrappers, to personal care products like perfumes, moisturizer, and liquid soap.

Phthalates have the general structural formula shown below:

R and R' represent alkyl groups.
If R and R' are both CH₃ (methyl) groups, the molecule is known as dimethyl phthalate (abbreviated as DMP).
If R and R' are both C₂H₅ (ethyl) groups, the molecule is known as diethyl phthalate (abbreviated DEP).
When R and R' are very small alkyl groups, like methyl or ethyl groups, the phthalates are colourless, odourless liquids at room temperature and pressure.
The phthalates are added to molten plastic, allowing the phthalates to mix with with the polymer. The polar C=O groups in the phthalate molecules interact with partial positive charges on atoms in the polymer chain, for example, the C^δ+ of the C-Cl covalent bond in a polyvinyl chloride polymer.
When the plastic is cooled, the interactions between the phthalate and the polymer chains remain, and the alkyl groups of the phthalate screen the polymer chains from interacting with each other so that the polymer chains can slide over each other. This results in a more flexible plastic.


Reference:
http://www.abc.net.au/news/2013-11-19/common-plastics-chemical-linked-to-pre-term-births/5101828

Further reading:
Esters and Esterification
Bond Polarity
Intermolecular Forces


Suggested Study Questions:

1. Draw the structural formula for
   • dimethyl phthalate
   • diethyl phthalate
2. Give the molecular formula for
   • dimethyl phthalate
   • diethyl phthalate
3. On the structural formula for dimethyl phthalate, circle a benzene ring.
4. On the structural formala for diethyl phthalate, circle an ester functional group.
5. Dimethyl phthalate can be prepared in an esterification reaction using phthalic acid and methanol. Draw the most likely structural formula for phthalic acid. 
6. In chemistry, what is meant by a polar bond?
7. On the structural formula of diethyl phthalate,  show the partial charges of the atoms in the polar areas of the molecule.
8. Draw a diagram to show the interaction between dimethyl phthalate and a section of the polyvinyl chloride polymer.

HPLC

AUS-e-TUTE has just added new resources for the High Performance Liquid Chromatography (HPLC) topic.
The new resources include a tutorial, game, test and exam.
Go to http://www.ausetute.com.au and log-in to start using these new resources.

The Chemistry Syllabus Study Guides for Queensland, New South Wales, Australian Capital Territory, Victoria, South Australia, and, AP Chemistry (USA and undergraduate) have been updated to include these new resources.

Links to the new resources have also been added from the Class/School Group index page.

Gas Chromatography Resources

AUS-e-TUTE has added new resources for the Gas Chromatography (GC) topic.
You will find links to the new tutorial, game, test and updated exams included in

• Test Centre index page (all members)
• Queensland syllabus study guide for chemistry (Australia)
• New South Wales syllabus study guide for chemistry  (Australia)
• Australian Capital Territory syllabus study guide for chemistry (Australia)
• Victorian syllabus study guide for chemistry (Australia)
• South Australian syllabus study guide for chemistry (Australia)
• AP syllabus study guide for chemistry (USA and undergraduate chemistry)
• Class/School Group index page

http://www.ausetute.com.au

A little MatheMagic is needed!

The University of Queensland's Faculty of Engineering  held a networking forum for teachers on 5th November 2013. They expressed a number of concerns regarding the High School graduates entering  the first year engineering course, and I think it's worthwhile highlighting one of those concerns here.

The main academic concern is that High School graduates do not have an adequate background in mathematics to cope with engineering. Now, they were very upfront about this, admitting that part of the problem was that they reduced the prerequisite from Maths C to Maths B in order to attract more school graduates to engineering. For those not familiar with the Queensland education "system", students present 6 final subjects, Maths B is one subject and Maths C is a separate , more advanced subject. Previously, engineering hopefuls would study Physics, Chemistry, Maths B, Maths C, English + 1 other subject. Now, they can present Physics, Chemistry, Maths B, English + 2 other subjects. The assembled teachers weren't very sympathetic to start with, why don't you just raise the prerequisite to Maths C again? Until we were presented with examples of the kind of maths some of the students seemed to be struggling with.
One of the examples we were given was that there were students who believed that if
a + b = -1 then that means that a = -b
and that is a huge concern! But raising the prerequisite wouldn't help, simply because any Maths student in senior high school should have no trouble realizing that a = -1 - b

I've had a similar discussion with a friend of mine who is a lecturer in nursing (at a different university). Her complaint is that High School graduates entering first year nursing often have difficulty with calculations involving drug doses. For instance, students have to decide how many tablets to give a patient given that a doctor has prescribed 100 mg of drug A four times a day, and that the hospital supplies brand X tablets each containing 50 mg of drug A.

High School chemistry and physics teachers are very familiar with this problem. There always seem to be atleast a few students in each class who appear to be quite good at maths judging by their report cards, but who don't seem able to handle fairly simply algebra when they leave the maths class.

Now, before the maths teachers start feeling indignant, let me say that this problem is not restricted to maths, and, unfortunately, it isn't even restricted to students. After the Engineering Faculty's presentation, I was chatting to a science teacher who was telling me about developments in the silicon chip industry that required "water that is so pure it is acidic".Curious, I followed up with a few questions, thinking that this teacher may have been using a definition of acid that I wasn't familiar with, but no, this teacher seemed to be using a Bronsted-Lowry definition.

So, the problem in a nutshell is that we are graduating students from schools with reasonable grades in maths who are not capable of rearranging an equation (and the much worse problem that there are teachers teaching science who don't seem to understand the concept of equilibrium and neutrality).
Clearly, any "learning" that has taken place is only at a very superficial level. How can we address this problem?

6 Random Questions Answered

Every so often, AUS-e-TUTE randomly selects 6 questions that have been asked in the last few hours by people who are not AUS-e-TUTE members.
Today's selection is:

1/ Question from Canada, "ammonia gas undergoes a combustion to produce nitrogen dioxide gas and water vapour. write and balance the equation"

Answer: 2NH₃ +⁷/₂O₂ → 2NO₂ + 3H₂O

2/ Question from USA, "How do you convert weight percent to mass fraction?"

Answer:  percent by mass (weight) = mass (weight) fraction x 100
 reference: http://www.ausetute.com.au/weightpc.html

3/ Question from USA, "what are the physical properties of metals due to metallic bonding?"
Answer:  The physical properties of solid metals are:

• conduct heat
• conduct electricity
• generally high melting and boiling points
• strong
• malleable (can be hammered or pressed out of shape without breaking)
• ductile (able to be drawn into a wire)
• metallic lustre
• opaque (reflect light)

Reference: http://www.ausetute.com.au/metallic.html

4/ Question from USA, "Can air be separated by physical means?"
Answer: Yes. Air is a mixture so it can be separated by physical means.
Reference: http://www.ausetute.com.au/chemphys.html

5/ Question from USA, "How do you calculate atomic mass from relative abundance?"
Answer: Given the relative atomic mass (r.a.m.) of an element and the mass of each of its isotopes, the relative abundance of each isotope can be calculated:
let y/100 = abundance of isotope 1
and (100 - y)/100 = abundance of isotope 2
then, r.a.m = [y/100 x mass isotope 1] + [(100 - y)/100 x mass isotope 2]
and solve for y
Reference: http://www.ausetute.com.au/atomicmass.html

6/ Question from USA, "How do you turn empirical formula into molecular formula?"
Answer: molecular formula = whole number x empirical formula
Reference: http://www.ausetute.com.au/empirical.html

Azobenzene: cis-trans isomers

A new soluble, light sensitive polymer has been created at the University of Helsinki. The polymer partially dissolves in water or certain alcohols, and, when exposed to light, the polymer switches to its cis isomer and dissolves completely.

This new polymer chain is known to contain azo compounds, and azo compounds are known for this ability to switch between cis and trans isomers using light.

Azo compounds are organic molecules in which two benzene rings (known as phenyl groups) are linked by two nitrogen atoms.
Azobenzene has the IUPAC name diphenyldiazene and is the simplest of the azo compounds.
When the 2 benzene rings (phenyl groups) are on the same side of the N=N bond this is known as the cis isomer. The structural formula for cis-azobenzene is shown below:

When the 2 benzene rings (phenyl groups) are on different sides of the N=N bond this is known as the trans isomer. The structural formula for trans-azobenzene is shown below:

The cis isomer is less stable than the trans isomer. In the presence of light (hν) , the trans isomer will convert to the cis isomer:

hν →

but because the cis isomer is less stable, it will relax back to the trans isomer over time:

→

Cis-azobenzene is more polar than trans-azobenzene so cis-azobenzene is more water soluble than trans-azobenzene.

Reference:
Szymon Wiktorowicz, Heikki Tenhu, Vladimir Aseyev. Using Light To Tune Thermo-Responsive Behavior and Host–Guest Interactions in Tegylated Poly(azocalix[4]arene)s. Macromolecules, 2013; 46 (15): 6209 DOI: 10.1021/ma4011457

Further Reading:
Cis-trans (geometric) Isomers

Suggested Study Questions:

1. Give the molecular formula for cis-azobenzene and trans-azobenzene.
2. Explain why azobenzene displays cis-trans (geometric) isomerism.
3. If the N=N bond in azobenzene was replaced with N-N, would the resulting molecule display cis-trans (geometric) isomerism? Explain your answer.
4.  On a drawing of the structural formula of trans-azobenzene, circle a phenyl group.
5. Diazene (diimine) has the molecular formula (NH)₂ . It contains the same N=N bond as azobenzene or diphenyldiazene. Diazene also displays cis-trans (geometric) isomerism. Draw both cis-diazene and trans-diazene.
6. Hydrazine has the molecular formula N₂H₄. Draw a possible structural formula for hydrazine. 
7. Do you expect hydrazine to display cis-trans (geometric) isomerism? Explain your answer.
8. Draw the molecular formula for the molecule trans-dibutyldiazene.
9. Dibutyldiazene undergoes an addition reaction with hydrogen gas. Draw the structural formula for the product of this reaction.

New AUS-e-TUTE Resources

AUS-e-TUTE has added new tutorials, games, tests and exams on the following chemistry topics:

• Types of Chemical Reactions

• Chemical and Physical Properties of Alkenes

• cis-trans (geometric) Isomers of Alkenes

• Structural (constitutional) Isomers of Haloalkanes (alkyl halides)

• Thin Layer Chromatography

The following syllabus study guides have also been updated:

• HSC chemistry
• VCE chemistry
• SACE chemistry
• AP chemistry
• A.C.T. chemistry
• QLD chemistry

Year 12 students preparing for the HSC, VCE or WACE  should also log-in to the Test Centre and use the exam preparation resources available for these courses.

6 Random Questions Answered

1/ Question From USA, "How do you calculate density for chemistry?"
Answer: density = mass/volume
(http://ausetute.com.au/density.html)

2/ Question from Canada, "What is the main functional group in aspirin?"
Answer: Aspirin (acetylsalicylic acid) contains a carboxyl and an ester functional group. The carboxyl group is responsible for the acidic properties of aspirin.
(http://ausetute.com.au/aspirin.html)

3/ Question from USA, "What is the magnetic quantum number for iron?"
Answer: Magnetic quantum number, m_l,  has a value from -l to +l
For iron (Z=26), m_l can have values of -2, -1, 0, +1, +2
(http://ausetute.com.au/quantum.html )

4/ Question from Australia, "What is the enthalpy of combustion of ethanol?"
Answer: 1367 kJ/mol
(http://ausetute.com.au/members/alkanolp.html)

5/ Question from Australia, "What is enthalpy of combustion?"
Answer: Enthalpy (or heat) of combustion of a substance is the amount of energy released when 1 mole of the substance combusts (burns) in excess oxygen at constant pressure.
(http://ausetute.com.au/members/heatcomb.html)

6/ Question from Australia, "How do you tell a non reducing sugar?"
Answer: Reducing sugars can be oxidised by mild oxidising agents, non-reducing sugars can not be oxidised by mild oxidising agents.
(http://ausetute.com.au/members/redsugar.html)

Spelling Mistakes vs Incorrect Science

It's that time of year in Australia when tens of thousands of students get ready to sit their final exams.
For many of these students it will be the first time they have sat an external assessment, that is, these exams will not be marked by teachers who know them. This time there will be no kindly teacher marking the exam paper and thinking, "oh dear, well I know what Chris really meant ....", this time a complete stranger will be sitting in front of your paper, and not only that, a complete stranger who has by now had to try to read and mark thousands of papers, and this stranger is only going to give you a mark based on exactly what you did write NOT on what he/she thinks you might have meant!

Which brings me to the subject of this discussion. 
When is a spelling mistake (typo) going to be marked as wrong on a Chemistry exam paper?
A spelling mistake will be marked wrong if it introduces ambiguity into your answer or if it makes what you are saying scientifically incorrect.

Spelling mistakes that will be probably not be marked as wrong include misplaced apostrophes, for example it's instead of its, or misspelling non-science-specific-words like using 'their' instead of 'there', as long as this does not alter the scientific meaning of what you have written.

Spelling mistakes that will definitely be marked wrong are those that make your answer scientifically "wrong".
In chemistry, changing just one letter in a word can have an enormous impact!
For example, ethane has the molecular formula C₂H₆ and is a saturated, and not very reactive, hydrocarbon. On the other hand, ethyne has the molecular formula C₂H₂ and is an unsaturated, and very reactive, hydrocarbon. Changing one letter, an a to a y, has a huge impact on the formula and properties of the compound! If you start writing about the addition of bromine to ethane instead of ethyne you will, and certainly should be, marked wrong.
Then there is the problem of capitalization, which is very important when writing chemical formula.
If you write Co then you have given the chemical symbol for the transition metal cobalt, but if you write CO you have given the molecular formula for the covalent compound carbon monoxide. Just using a lowercase letter instead of a capital (uppercase) letter  has changed the substance from a metallic element to a covalent compound! So, if you start talking about the metallic bonding of CO in the solid state at room temperature and pressure, you will be marked wrong.

After you have written an answer to an exam question, read the question again. Then read your answer. Make sure you have written an answer to the question that was asked, and, make sure that your answer says what you meant it to say! Be on the look-out for those spelling mistakes (typos) that could lose you marks.

Nobel Prize in Chemistry 2013

Martin Karplus, Michael Levitt and Arieh Warshel have been awarded the 2013 Nobel Prize in Chemistry "for the development of multiscale models for complex chemical systems", that is, they have made it possible to model complex chemical reactions using computers.

When light hits the retina in your eye, the free electrons in retinal are filled with energy, which changes the shape of the molecule. This is the first stage in the process of your sense of sight.
In 1972, Karplus and Warshel modelled retinal by developing a computer program that used quantum  physics when it performed calculations on free electrons and then used classical physics for all electrons and all atomic nuclei. This was the first time that anyone had managed to bring about a chemically relevant collaboration between classical and quantum physics.

Enzymes are crucial to life, but in order to simulate the reactions of enzymes, a computer program would need classical and quantum physics to collaborate more smoothly. In 1976 Levitt and Warshel successfully simulated an enzymatic reaction, and this program would work for any kind of molecule.

The use of computers to simulate chemical reactions is increasingly important as a tool for understanding how reactions occur and the paths the reactants take. Computer programs can be used to optimize chemical process in order to produce better solar cells, improve catalysts in motor vehicles, develop more effective drugs, and so much more.

Reference:
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2013/popular-chemistryprize2013.pdf

Further Reading:
Enzymes: http://ausetute.com.au/members/enzymes.html 
Proteins: http://ausetute.com.au/members/proteins.html
 

Nobel Prize Facts 2013

Alfred Nobel was a Swedish Chemist and the inventor of dynamite. The fortune that he made from this during his lifetime, about SEK 31 million (today about SEK 1,702 million or about $265 million), was left in his will to institute the Nobel Prizes. One of these prizes is awarded to "the person who shall have made the most important chemical discovery or improvement". The announcement regarding the award of Nobel Prizes is made in October each year.
While we wait for this years announcement, here are a few facts about the Nobel Prize in Chemistry:

• 104 Nobel Prizes in Chemistry have been awarded since 1901.
• A Nobel Prize in Chemistry was not awarded in 1916, 1917, 1919, 1924, 1933, 1940, 1941 and 1942
• 63 Chemistry Prizes have been given to one Laureate only
• 23 Chemistry Prizes have been shared between 3 Laureates. 
• A Nobel Prize in Chemistry can not be awarded to more than 3 people in each year.
• 162 individuals have been awarded the Nobel Prize in Chemistry (these people are called Laureates).
• 1 person, Frederick Sanger, has been awarded the Nobel Prize in Chemistry twice.
• 4 women have been awarded the Nobel Prize in Chemistry:
  • Marie Curie 1911
  • Irene Joliot-Curie 1935
  • Dorothy Crowfoot Hodgkin 1964
  • Ada Yonath 2009
• 2 Chemistry Laureates have been awarded Nobel Prizes in other areas as well:
  • Marie Curie (Physics 1903, Chemistry 1911)
  • Linus Pauling (Chemistry 1954, Peace 1962)
•  1 person, Linus Pauling, is the only person who has been awarded 2 unshared Nobel Prizes.
• 4  Nobel Prize Families:
  • Marie and Pierre Curie - husband and wife (Physics 1903)
  • Irene Joilot-Curie and Frederic Joliot - husband and wife (Chemistry 1935)
  • Hans von Euler-Cheplin (father, Chemistry 1929) and Ulf von Euler (son, Medicine 1970)
  • Arthur Kornberg (father, Medicine 1959) and Roger D. Konberg (son, Chemistry 2006)
• Average age of all Chemistry Laureates is 57
• Youngest Chemistry Laureate was Frederic Joliot who was 35 years old when awarded his Nobel Prize in 1935 (together with his wife Irene Joliot-Curie)
• Oldest Chemistry Laureate was John B. Fenn who was 85 years old when he was awarded the Nobel Prize in Chemistry in 2002.
• 0 posthumous Nobel Prizes in Chemistry. A Nobel Prize cannot be awarded posthumously unless death occurred after the announcement of the Nobel Prize.
• 2 Nobel Laureates in Chemistry have been forced by authorities to decline the Nobel Prize. Adolf Hitler forbade Richard Kuhn (Chemistry 1938) and  Adolf Butenandt (Chemistry 1939) from receiving their Nobel Prizes.

Reference:
http://www.nobelprize.org/nobel_prizes/facts/chemistry/

6 Random Questions Answered

If you are an AUS-e-TUTE member you can just ask us a question and we'll do our best to answer it in a meaningful way, but, if you are not an AUS-e-TUTE member you'll have to resort to asking a search engine, and if you are lucky, we might answer your question here (if you have encrypted your search, for example if you are logged into a gmail account when you search google, we can't answer your question here).

Question from USA, "a substance that cannot be separated into simpler substances by physical or chemical mean is an it a mixture"
Answer from ausetute.com.au Yes, a substance that cannot be separated into simpler substances by physical means is a pure substance and not a mixture. If the pure substance can be separated by chemical means, then it is a compound and not an element.
Reference: http://ausetute.com.au/puresubs.html
http://ausetute.com.au/elements.html

Question from USA, "what is the density of a substance with a mass of 47.2 g and a volumn of 36 mL ?"
Answer from ausetute.com.au density = mass(g)/volume(mL) = 47.2/36 = 1.31g/mL
Reference: http://ausetute.com.au/density.html

Search from Canada, "what are some princeples of pure substance and mixturs"
Reply from ausetute.com.au "Mixtures can be separated by physical means. Pure substances cannnot be separated into their component parts using physical means"
Reference: http://ausetute.com.au/puresubs.html

Search from Malaysia, "why stable compound release less energy"
Reply from ausetute.com.au "Breaking bonds requires energy, making bonds releases energy. The more energy that is required to break the bonds, the more stable the compound will be."
Reference: http://ausetute.com.au/members/heatbond.html

Search from USA, "density of elements between 3.0g/ml and 6.0g/ml"
You can look these up for yourself here http://www.ausetute.com.au/members/ptablei.html

Search from USA, " electron neon orbitals"
Response from ausetute.com.au Do you want the set of orbitals (s and p orbitals) or the electron configuration of neon (1s² 2s² 2p⁶)?
Reference: http://www.ausetute.com.au/econfig.html

Propene on Titan

 Titan, one of Saturn's moons, is very special. It is the only satellite in our solar system that has a fully developed atmosphere.
Hydrocarbons were first detected in the atmosphere of Titan by NASA's Voyager 1 spacecraft way back in 1980. Titan's atmosphere is made up of 98.4% nitrogen gas and 1.4% methane. Sunlight breaks this methane apart and the fragments then link up to form chains with 2, 3 or more carbon atoms in the chain. Voyager found the presence of propane and propyne, but not propene.

More recently, NASA's Cassini spacecraft's mass spectrometer data suggested that propene might be present in Titan's upper atmosphere, and in 2013, using a form of infrared spectroscopy, propene was indeed found in Titan's atmosphere.

On planet Earth, propene is second only to ethene as a starting product in the petrochemical industry. About two thirds of all the propene produced is used to make the plastic known as polypropene, or polypropylene, which is used widely in packaging materials.

Reference:
C. A. Nixon, D. E. Jennings, B. Bézard, S. Vinatier, N. A. Teanby, K. Sung, T. M. Ansty, P. G. J. Irwin, N. Gorius, V. Cottini, A. Coustenis, F. M. Flasar. DETECTION OF PROPENE IN TITAN'S STRATOSPHERE. The Astrophysical Journal, 2013; 776 (1): L14 DOI: 10.1088/2041-8205/776/1/L14

Further Reading
http://ausetute.com.au/namctut1.html
http://ausetute.com.au/namsanes.html
http://ausetute.com.au/namsenes.html
http://ausetute.com.au/namsynes.html
http://ausetute.com.au/members/polymers.html
http://ausetute.com.au/members/polythen.html

Suggested Study Questions:

1. What is meant by the term "hydrocarbon"?
2. Give the molecular formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne
3. Give the structural formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne 
4. Propene is used to produce polypropene (polypropylene). Draw a representative section of polypropene.
5. Would you describe the polymerisation of propene as an addition polymerisation or as a condensation polymerisation? Explain your answer.
6. Ethene is used to produce polythene or polyethylene. Draw a representative section of polythene.
7. Would you describe the polymerisation of ethene as an addition polymerisation of as a condensation polymerisation? Explain your answer.
8. Both ethene and propene have been found in Titan's atmosphere. Do you think it is likely that polythene and polypropylene will be found in Titan's atmosphere? Explain your answer.

Cyclodextrin

Researchers at Temple University's Water and Environmental Technology (WET) Center have been investigating the use of cyclodextrins in the treatment of waste water.
Cyclodextrins are made up of sugar molecules, bonded together to form a ring. An example of the structure of a cyclodextrin, alpha-cyclodextrin which is a 6-membered sugar ring, is shown below:

Cyclodextrins can be used in water treatment because they can bond to substances such as toxic organic compounds or heavy metals and hold them inside the ring structure. Owing to the many polar OH functional groups, cyclodextrins are water soluble, but the researchers have produced insoluble materials by coating a thin layer of cyclodextrin on sand, glass, silica and filter paper. Doing this allows the absorbent material to be collected, washed and re-used.

Reference:
Temple University (2013, September 24). New adsorbent is more effective and environmentally friendly for treating wastewater. ScienceDaily. Retrieved September 30, 2013, from http://www.sciencedaily.com­ /releases/2013/09/130924174152.htm

Further Reading
Carbohydrates: http://ausetute.com.au/members/sugars.html 
Functional Groups: http://ausetute.com.au/fungroup.html
Solubility: http://ausetute.com.au/intermof.html

Zeolites: http://ausetute.com.au/members/zeolites.html
Polymers: http://ausetute.com.au/members/polymers.html 

Suggested Study Questions:

1. What does the "cyclo" part of the name in cyclodextrin refer to?
2. Use the structure above to determine the molecular formula for alpha-cyclodextrin.
3. Use the molecular formula to determine the empirical formula for alpha-cyclodextrin.
4. Calculate the percentage composition of alpha-cyclodextrin.
5. Draw the structure of alpha-cyclodextrin and locate and identify the functional groups.
6. Use a diagram to explain how alpha-cyclodextrin dissolves in water.
7. Use a diagram to explain how alpha-cyclodextrin could be used to remove lead ions from water.
8. Draw the structure of alpha-cyclodextrin an clearly identify all 6 of the sugar molecules making up the structure. 
9. Activated carbon is commonly used to remove contaminants from water. What benefits do you think there might be in using cyclodextrin-derived absorbant materials instead of activated carbon? 

Why Use a Volumetric Flask?

In order to prepare an aqueous standard solution, you transfer the solute to a volumetric flask and then you add water "up to the mark", that is, until the bottom of the meniscus lies on the "mark" when viewed at eye-level. You can quickly convince yourself of the need to view the "mark" at eye-level just be preparing your standard solution as above and then changing the angle you view it from.
But what about this need to add water to the solute in this oddly-shaped vessel called a volumetric flask?
Why couldn't you just weigh out the solute into a beaker then add the required volume of water from a pipette?
Or, if the solute is a liquid or a solution, why not just pipette the required volume into a beaker then pipette the required volume of solvent into the same beaker?

So, why not try it?

Experiment (a) For solid solutes such as sodium chloride (table salt) or sucrose ("sugar") just pour the solid into a small DRY measuring cylinder until you have 5 mL for example. Pour this solid into a 100 mL measuring cylinder. Add 50 mL of water from a pipette (you will need to keep swirling the flask while you add the water). Record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using sand as the "solute" and water as the solvent.

Experiment (b)  For liquid solutes such as ethanol (ethyl alcohol) or acetone (propanone) use a pipette to place 50 mL of the solute into a 100 mL measuing cylinder then add 50 mL of water from a pipette and record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using vegetable oil as the "solute" and water as the solvent.

If a solute dissolves in a solvent, the volume of the final solution is not equal to the volume of the solute plus the volume of the solvent. Sometimes adding a solute to a solvent results in a solution with a volume less than that of the solvent + solute, and sometimes adding a solute to a solvent results in a solution with a volume greater than that of the solvent + solute. Right now, there are no good, general theories to explain this behaviour! But it is because of this that we use that oddly shaped piece of glassware called a volumetric flask when we make up a standard solution.

Acetylene by Accident

Before the discovery of acetylene, it could take 7 men 10 days to chip out a porthole on a steel ship.
With the invention of the oxy-acetylene torch, it took 1 man 12 minutes to cut out the same porthole!
The oxy-acetylene torch that revolutionised the building industry would never have been invented had it not been for a series of accidents which started in 1836......
......read more in the September 2013 issue of AUS-e-NEWS.

If you would like to subscribe to AUS-e-TUTE's quarterly newsletter, please email

using "subscribe" as the subject.

Help for Students

AUS-e-TUTE has updated its "Student Help" and "School Help" pages.
Now there are more instructions for students on how to use AUS-e-TUTE's resources, including specific instructions for keyboard/mouse-devices and touchscreen-devices (iPads and iPhones included).
We've also added a new page to make it easier for students and teachers registered with a class or school group to access the interactive learning activities (scaffolded activities) and online quizzes.
Just click on a Class/School Log-in to see the new page.

Kinetic Energy Distributions

New kinetic energy, or Maxwell-Boltzman, distribution resources are now available at :

http://www.ausetute.com.au

Members can log-in to access the new tutorial, game, test and exam.

Heat of Neutralisation

AUS-e-TUTE has added a new tutorial, game, test and exam on the topic of heat of neutralisation.

Visit http://www.ausetute.com.au and log-in.
The new resources are in the Thermochemistry section.

Introduction to Buffers

AUS-e-TUTE has just uploaded two new sets of resources:

• Buffer Concepts (tutorial, game, test, exam)
• pH of Salt Solutions (tutorial, game, test, exam)

There has also been a significant update to the tutorial on Titration Curves (Graphs) with improved graphs and explanations.

Members should log-in and go to the Acid and Base section to find these new resources.

New Polyamide Resources

AUS-e-TUTE has just added new resources for synthetic polyamides (nylons).
Members can log-in to use the new tutorial, game, test and exam.

Concentration of Calcium Ions in Hard Water

AUS-e-TUTE has just added new complexometric titration resources for the determination of calcium ions in hard water.
Members should log-in to see the new tutorial, game, test and drill.

New Titration Resources

AUS-e-TUTE has just added new Complexometric Titration resources for the determination of calcium and magnesium ions in hard water.
Members can log-in to use the new tutorial, game, test and drill.

ausetute.com.au

Methanol and the Home-Brewer

In June 2013, a young man in Queensland died as a result of drinking homemade liquor. It is believed that the liquor contained a toxic level of methanol (also known as wood alcohol). Drinking 10 mL of pure methanol can cause permanent blindness, drinking 30 mL of methanol can kill you.

The first step in the production of homemade liquors, is the fermentation of sugar.
Methanol, CH₃OH,is formed during fermentation.
When fermenting 6 kg of sugar dissolved in water for the production of distilled spirits such as whiskey or vodka, the home-brewer (and home-distiller) will typically find that the concentration of methanol in their brew is about 3 parts per million.

Many fruits are used by the home-brewer as the source of sugar to be fermented. Each fruit will lend a distinctive flavour to the final product. But fruits that are high in pectin will produce greater concentrations of methanol. Apples, apricots, guavas, quinces, plums, gooseberries, and citrus fruits like oranges, all contain high levels of pectin, typically more than 1% by mass pectin. Grapes, cherries and strawberries contain low levels of pectin, less than 1% by mass pectin.

Pectin contains  galacturonic acid which has the structural formula shown below:

In pectin, about 80% of the carboxyl groups in galacturonic acid are esterified with methanol. The remaining non-esterified carboxyl groups exist as the acid, or as salts with sodium, potassium or calcium. When pectin is broken down by enzymes during the brewing process, the methyl esters react with water to produce methanol.

The second step in the production of homemade liquor is the distillation step.
This is the crucial step in removing as much of the toxic methanol as possible.
The boiling point of methanol is about 65^oC, but the boiling point of ethanol (the desired product) is about 78^oC. During the distillation process, the first fraction collected should contain the methanol. This fraction should be collected and discarded. The next fraction should contain the desired liquor. It is highly recommended that any distillate collected after about 96^oC also be discarded.


Reference:
http://www.couriermail.com.au/news/queensland/ballandean-man-bill-lynam-who-lost-his-son-joel-to-homemade-liquor-poisoning-is-thankful-that-other-son-joshua-survived/story-fnihsrf2-1226664893229

Further Reading
http://ausetute.com.au/members/alkanolp.html (members only tutorial on alkanols)
http://ausetute.com.au/members/carboxyl.html (members only tutorial on alkanoic acids) 
http://ausetute.com.au/partspm.html 
http://ausetute.com.au/density.html 

Suggested Study Questions:

1. Draw the structural formula for methanol.
2. Locate the functional group present in methanol on the structural formula above. Name the functional group. 
3. At 25^oC methanol has a density of  0.79 g mL^-3. Calculate the mass of methanol present in a lethal dose of pure methanol .
4.  Convert the concentration of methanol given for homemade whiskey into a concentration in g mL^-1.
5. Assume the young man who died drank homemade whiskey. What minimum volume of homemade whiskey did he drink?
6. For galacturonic acid given the:
   • molecular formula
   • molar mass
7.  On the structural formula for galacturonic acid identify and name the functional groups present.
8. Draw the structure for the sodium salt of galacturonic acid.
9. Draw the structure for galacturonic acid esterified with methanol.
10. Give the molecular formula and molar mass for the structure above.
11. Apples contain about 1% by mass pectin. 10 kg of apples are to be used in the production of a homemade liquor. What mass of pectin will be present?
12. Assume exactly 100% of the carboxyl groups in galacturonic acid are esterified with methanol. How many moles of the ester are present in 10 kg of apples?
13. Write an equation representing the reaction between this ester and water to form methanol  and galacturonic acid.
14. How many moles of methanol could be produced by the break down of pectin in 10 kg of apples?
15. Assuming the young man who died had drunk this apple concoction without distilling and removing the methanol, what minimum volume of fermented apple-drink would he have had to have drunk?
16. Why do you think most countries have outlawed home-distilling?

AUS-e-NEWS June 2013

Have you ever noticed that the price of E10 fuel, also known as gasohol, is less than the price of petrol (gasoline) ?

Just today, when I went to put fuel into my car, the price for standard unleaded petrol (ULP) was 130.6 cents per litre while the price of E10 fuel was 128.4 cents per litre.

Will using E10 instead of ULP save me money?

Read the June 2013 edition of AUS-e-NEWS to find out!

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