Which of the following is an acid-base indicator?

Question: Which of the following is an acid-base indicator?

1. hydrochloric acid 
2. sodium hydroxide 
3. water 
4. phenolphthalein

Answer: Phenolphthalein is an acid-base indicator

1. Hydrochloric acid is an acid
2. Sodium Hydroxide is a base
3. Water is neutral

What is the best indicator for titration?

Question: What is the best indicator for titration?
Answer: That all depends on what you are titrating!

If you doing an acid-base titration, then you will need to know the relative strengths of the acid and base you going to be using.
Once you have determined an approximate pH for the equivalence point of the neutralisation reaction, you use this as the pH of the endpoint of the titration in order to determine the best acid-base indicator to use.

Packing Heat the Chemistry Way

Have you ever twisted your ankle or been bruised while playing sport?

The first thing you probably did was place an instant cold pack on the injury.

Sore, aching muscles? There's an instant heat pack for that!

The chemistry of instant cold packs and instant heat packs is discussed in the June 2015 issue of AUS-e-NEWS.

Contact us if you have not received your June 2015 AUS-e-NEWS yet.

Buy and Sell Essays

If you want to know where to go to buy a high school-level essay suitable for use in Australia, the Sydney Morning Herald has a number of suggestions, with some indication of prices:
http://www.smh.com.au/national/education/cheating-endemic-in-nsw-high-schools-20150607-ggw8h9

A couple of years ago I went to a high school science teachers workshop, where, over lunch, I shocked a number of teachers of physics and chemistry by telling them how easy it was for students to buy their "extended experimental investigation" online, and, how cheap it was. My point in doing this was not to shock the teachers (I thought everyone knew about this), it was to point out that the notion of using this type of investigation as an assessment tool was not assessing students' scientific abilities it was only assessing their ability to find relevant information online (arguably just as important and useful in its own right). Unfortunately, as an assessment tool, it also favours those with money to spend. The answer is not to try to "crack down" on this "cheating", which, although possible would almost certainly not be practical, rather the answer is to change the way students are assessed.

There is probably a much more deeply-rooted problem in all of this "cheating". I strongly suspect that for many students, there is no joy in learning or indeed in trying to understand concepts, the only purpose for going to school and doing assessments, is to get a good mark in order to go somewhere else after school (university, TAFE).(No doubt, the only reason they want to go to a tertiary education institution is in order to get a good mark in order to go somewhere else again ..... and it is entirely possible they will spend the rest of their lives being dissatisfied and buying their way to "somewhere else").
Perhaps if we could take everyone's focus off "assessment", and get them to focus on "learning", students might find that not only is there a lot of fun to be had out of learning something new, there is also an intense sense of satisfaction when you realise that you now understand a concept well enough to use to it in different situations, and, there is an enormous sense of power in using your understanding to make and test predictions. They might even find the learning process enjoyable.

Sucralose and Acesulfame potassium

Artificial sweeteners,  especially aspartame, have hit the news headlines once again with PepsiCo's decision to start selling Diet Pepsi without aspartame from August 2015 in the USA. The aspartame is to be replaced by a blend of sucralose and acesulfame potassium.

Sucralose was discovered in 1976 when Shashikant Phadnis at Queen Elizabeth College was asked to "test" a chlorinated sugar compound but he thought he'd been asked to "taste" it, so he did, and found it be very sweet! Sucralose, shown on the right, is synthesised from sucrose in a number of steps in which 3 of sucrose's hydroxyl groups are substituted for chlorine atoms.
Although sucralose is about 300 times sweeter than sucrose, it is not broken down during digestion and therefore does not contribute to ingested calories (kilojoules).
Splenda is a brand name for a common sucralose-based sweetener.


Acesulfame potassium was accidentally discovered in 1967 by German chemist Karl Clauss, who found it to be sweeter than sucrose. It is not as sweet as sucralose, however, and is often used in combination with other artificial sweeteners such as aspartame or sucralose. It has the structural formula shown below:

Acesulfame potassium is currently sold under the brand names Sunette, Sweet One and Sweet 'n Safe and is found in many "sugar-free" foods such as chewing gum, jelly (Jell-O), even in alcoholic drinks.

Reference:
http://www.smh.com.au/business/retail/diet-pepsi-dumps-aspartame-as-consumer-backlash-hurts-sales-20150425-1msz1b.html

Further Reading:

• http://www.ausetute.com.au/sugars.html 
• http://www.ausetute.com.au/proteins.html
• http://www.ausetute.com.au/fungroup.html
• http://www.ausetute.com.au/intermof.html
• http://www.ausetute.com.au/skeletal.html
• http://www.ausetute.com.au/structural2D.html
• http://www.ausetute.com.au/condensedsf.html
• http://www.ausetute.com.au/molecularformula.html

Suggested Study Questions:

1. What is the molecular formula for:
   • sucralose
   • sucrose
   • acesulfame potassium
2. Draw the structural formula for sucrose and circle the hydroxyl functional groups.
3. Draw the structural formula for sucralose and
   • circle the hydroxyl functional groups in red
   • circle the halogen functional groups in green
   • circle any other functional groups blue and name them 
4. What class of compounds does sucrose belong to?
5. Draw the structural formula for acesulfame potassium and identify the functional groups.
6. Is it appropriate to call acesulfame potassium a potassium salt? Explain your answer.
7. Aspartame is the methyl ester of a didpeptide. What functional groups do you expect the aspartame molecule to have? Explain your answer. 
8. Do you expect sucralose and acesulfame potassium to be soluble in water? Explain your answer.

Effect of Temperature on Solubility

What happens to the solubility of a salt or a gas at constant pressure when the temperature of the solution changes?
This can be treated as just a special case of Le Chatelier's Principle .....

And AUS-e-TUTe has just added new resources to help you understand the effect of temperature on solubility.
AUS-e-TUTE Members should log-in to use the new tutorial (includes a drill), game, test and exam.

If you are not an AUS-e-TUTE member, there is non-interactive "free-to-view" tutorial currently available for evaluation purposes at http://www.ausetute.com.au/solubilitylcp.html


Get a better understanding of concepts in chemistry, and improve your problem solving ..... join AUS-e-TUTE today!

Solutes, Solvents and Solutions

Seems like the science of solutions is simply seething with "s" sounds:

• solute
• solvent
• solution
• solubility
• solvation
• saturated (and unsaturated)

 but what do they mean?

AUS-e-TUTE has just added new resources to help you find out, and, understand the differences!
AUS-e-TUTE Members should log-in to use these new "Solutions Concepts" resources.

Not an AUS-e-TUTE Member?
A free-to-view tutorial is currently available on this topic for evaluation purposes at http://www.ausetute.com.au/solutions.html

When you're serious about learning some chemistry, join us at www.ausetute.com.au