Underwater Bubbles

 A backyard experiment you can do that will help you see Boyle's law in action.

https://www.youtube.com/watch?v=aHvGtWXTdso

 You will find more information in the feature article about SCUBA diving in the June 2022 issue of AUS-e-NEWS.

Let's Go SCUBA Diving

In 2021, Mitchell Goodwin, an experienced SCUBA diver, was diving off the coast of Mandurah in Western Australia. According to the report in the "West Australian", he descended to a depth of 42 m and stayed at this depth for 27 minutes. On his ascent, he made one decompression stop. When he got back to the boat he felt nauseous, lost his hearing, his sight, and blacked out.

What had gone wrong?

Read more in the June 2022 edition of AUS-e-NEWS.

Subscribe to AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter for chemistry students and teachers, at https://www.ausetute.com.au/ausenews.html

Converting Between Concentration Units

The concentration of carbon dioxide dissolved in water is about 0.000011 mol/L, while the concentration of carbon dioxide in blood is about 1100 ppm. It is not easy to tell which of these two solutions is the most concentrated because they are in different units. However, if we were to convert the concentration of carbon dioxide in water from mol/L to ppm, we could easily compare these two concentrations.

AUS-e-TUTE has just added a new tutorial, game, test, drill, prac, flashcards, quiz, worksheet wizard, and problem solving template to help!

 

Members should log-in to use these new resources: https://www.ausetute.com.au

 

If you are not an AUS-e-TUTE member you can view the tutorial for free at https://www.ausetute.com.au/concconv.html

Chinese Milk Scandal

 When we buy food from a shop, we assume that food is safe to eat, but sometimes it isn't!

In 2008 six babies died from kidney stones and an estimated 54,000 babies were hospitalized in China after being fed "Infant Formula" (baby milk) adulterated with melamine, an industrial chemical. It is thought that about 300,000 babies in total were affected by what came to be known as the "Chinese Milk Scandal".

Why was melamine added to Infant Formula? And why did it take so long to discover its addition?

Read more in this edition of AUS-e-NEWS:

Subscribe to AUS-e-NEWS at https://www.ausetute.com.au/ausenews.html

 

SI Units for Chemistry Students

What is an SI unit?

What is the SI Unit of mass?

Is ms a metre second or a millisecond?

Is V the symbol for electric potential or volts?

The answers to these and other questions about SI units can be found at https://www.ausetute.com.au/siunits.html

AUS-e-TUTE members should log-in to use the new SI Unit learning resources, including digital flash cards.

Mass Concentration (m/v)

 There are lots of ways to measure concentration in chemistry.

One method is to divide the mass of solute by the volume of solution: m/v

This is called a mass concentration and common units for mass concentration are g/L or g L^-1

AUS-e-TUTE has just added new teaching and learning resources for mass concentration calculations (game, test, drill, quiz, worksheet and problem solving template).

Members should log-in to use these new resources.

Non-members can go to the "free-to-view" tutorial at https://www.ausetute.com.au/massconc.html

Energy from Hydrogen

Hydrogen releases a lot of energy when it combusts, so much energy that it is hoped we will be able to use it to power our future.

Where does all that energy come from?

Read the June 2021 edition of AUS-e-NEWS to find out more.

Subscribe for free at https://www.ausetute.com.au/ausenews.html

Chemical Equations for Equilibrium Reactions

 

When do you use single arrow → in a chemical equation and when do you use a double-headed arrow ⇌ in a chemical equation?

Go to https://www.ausetute.com.au/equilibriumeqtn.html to find out!

 

AUS-e-TUTE Members should log-in to use the new Writing Chemical Equations for Equilibrium Reactions tutorial, game, test and exam with worked solutions.

Coming to terms with chemical equilibrium

In order to understand chemical reactions, you are going to have to come to terms with an important concept, that is, chemical equilibrium.

In AUS-e-TUTE's new set of resources (tutorial, game, test and exam questions with worked solutions) we look at how the type of system (open or closed) and the type of reaction (reversible or irreversible) determines whether a system can achieve a state of balance otherwise known as chemical equilibrium.

AUS-e-TUTE members should log-in to use these new resources.

If you are not an AUS-e-TUTE members you can view the tutorial for free at 

https://www.ausetute.com.au/equilibriumsystem.html

Reversible and Irreversible Changes

 Physical changes are, in general, reversible, but only some chemical changes are reversible while others are irreversible.

AUS-e-TUTE has just added new resources to help you classify changes as reversible or irreversible.

AUS-e-TUTE members should log-in to use the new resources.

If you are not an AUS-e-TUTE Member you can access a "free-to-view" tutorial at https://www.ausetute.com.au/reversible.html

pH After Mixing Weak Acids

 Acetic acid is a weak acid (K_a = 1.8×10^-5).  The pH of 100 mL of 0.10 mol L^-1 acetic acid is 2.9.

Hydrocyanic acid is a weak acid (K_a=6.3×10^-10). The pH of 100 mL of 0.10 mol L^-1 hydrocyanic acid is 5.1.

But what is the pH of the resultant solution if you mixed these two weak acids together?

AUS-e-TUTE has just added new resources to help you understand how to calculate the pH of solutions after mixing weak acids together. AUS-e-TUTE Members should log-in to access the new tutorial, game and test with worked solutions.

If you are not yet an AUS-e-TUTE member, you can access the "free-to-view" tutorial at https://www.ausetute.com.au/phmixwa.html

What is an indicator?

What is an acid-base indicator?

What does it do?

Where do we use acid-base indicators?

These and other questions about acid-base indicators can be answered at 

https://www.ausetute.com.au/indicators.html

AUS-e-TUTE Members also have access to the game, test and exam with worked solutions on this topic.

Join AUS-e-TUTE Today!

Brønsted-Lowry Theory of Acids and Bases

 Ammonia, NH₃, is a base right?

Well, yes it is sometimes... but it can also be an acid.

Welcome to the wonderful world of Brønsted-Lowry acids and bases.

At AUS-e-TUTE, we've just added a new tutorial, game, tests and exam to help you understand Brønsted-Lowry acids, bases and their conjugates.

If you are not an AUS-e-TUTE Member you can view a tutorial on this subject for free at https://www.ausetute.com.au/bronstedlowry.html

pH of a Solution When Weak Acid and Strong Base are Mixed

What happens to the pH of a weak acid as you add strong base to it?

For example, aqueous sodium hydroxide solution (NaOH_(aq)) is a strong base and acetic acid (CH₃COOH_(aq)) is a weak acid.

If you add 10 mL of 0.20 mol/L NaOH_(aq) to 25 mL of 0.10 mol/L CH₃COOH_(aq), what is the pH of the resultant solution?

Find out how to work this out, and work through other examples with worked solutions at AUS-e-TUTE.

A "free-to-view" tutorial is available at https://www.ausetute.com.au/phmixwasb.html

AUS-e-TUTE Members should log-in to play the new game, do the test and get repetitive endless practice with the new drill.

Elimination of HX from Haloalkanes

One way to synthesize alkenes is to remove hydrogen halide (HX) from a haloalkane (alkyl halide) in an elimination reaction.

Learn how in AUS-e-TUTE's new tutorial Dehydrohalogenation of Haloalkanes

AUS-e-TUTE Members should log-in to play the game and take the test (with immediate feedback and worked solutions).

Classification of Haloalkanes

Question: How do you classify haloalkanes (alkyl halides) as primary, secondary or tertiary?

Answers at https://www.ausetute.com.au/rxclassify.html

Test your knowledge of how to classify haloalkanes with AUS-e-TUTE's games and tests (with instant feedback and worked solutions!). Find out more at https://www.ausetute.com.au/register.html

Monoprotic acid pH with a concentration of 0.022M

Question: What is the pH of a monoprotic acid with a concentration of 0.022 M?

Answer:
1. Assume this is a strong monoprotic acid so that it fully dissociates: HA → H⁺ + A^-

2. [HA] = [H⁺] = 0.022 M

3. pH = -log₁₀[H⁺] = -log₁₀[0.022] = 1.7

Find out more, and see questions with worked solutions, at https://www.ausetute.com.au/phstronga.html

What is the weight/volume percent (w/v) of a solution prepared from 50 g NaCl and 2.5 L of water?

Question: What is the concentration, weight/volume percent (w/v), of a solution prepared from 50. g NaCl and 2.5 L of water?

Answer:
1. w/v % is a measure of the concentration of a solution.
Units are often given as g solute/100 mL solvent.

2. w/v% = (mass solute in grams/volume of solution in mL) × 100

3. w= mass solute = 50 g
v = volume of solution = 2.5 L = 2.5 L × 1000 mL/L = 2500 mL (assuming the NaCl does NOT increase the volume as it dissolves in the water)

4. w/v% = (50 g/2500 mL) × 100 = 2 g/100 mL

Find out more, and see worked solutions to questions, at https://www.ausetute.com.au/wtvol.html

Why is the heat of formation for gaseous oxygen equal to 0?

Question: Why is the heat of formation for gaseous oxygen equal to 0?

Answer:
1. The standard heat of formation of any compound is defined as the enthalpy change for the compound when it is formed from its elements in their standard states.

2. Gaseous oxygen (O_2(g)) is a molecule (not a compound). The standard state for oxygen is as a gas, O_2(g).

3. There is no need to change gaseous oxygen, O_2(g) into its standard state because that is how it exists under standard conditions, therefore its heat of formation is 0.

Find out more at, and see worked examples, at https://www.ausetute.com.au/heatform.html

How to know what species will spontaneously react in redox reactions

A redox reaction is spontaneous if the standard electrode potential is positive,
that is,
if E^o_(reaction) > 0

Find out more, and look at a worked example, at: https://www.ausetute.com.au/redoxspon.html