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

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

Explosive Medicine

You’ve probably heard of Alfred Nobel, the inventor of dynamite and gelignite. The commercialisation of these explosives enabled him to accumulate great wealth during his lifetime which, by the terms of his will signed in 1895, was used to establish the Nobel Prize. In later life he was prescribed Trinitrin, a medication used to relieve a heart condition known as angina.

What do dynamite, gelignite and Trinitrin all have in common?

They all contain nitroglycerin!

This is not a story about the life of Alfred Nobel.

It is a story about the fascinating chemistry of nitroglycerin…

Read more in the June 2018 issue of AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter for chemistry students and teachers.

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

Energy Content of Food

As I read the"nutritional information" panel on my box of cereal this morning I wondered how you would measure the "energy content" of food.
At AUS-e-TUTE we've come up with a straight-forward experiment that you could do in the school laboratory (or at home if you really wanted too!). We even provided some sample results and calculations so that you can measure the energy content of your favourite foods.

If you are an AUS-e-TUTE Member, you will also find additional resources such as a game, test and drill with worked solutions to help you prepare for your exams.

If you are not an AUS-e-TUTE member, you can access a "free-to-view" tutorial for evaluation purposes at http://www.ausetute.com.au/heatfood.html

Biodiesel

What's the difference between diesel and biodiesel?
I'm glad you asked!
AUS-e-TUTE has just added new resources (tutorial, game, test, exam) to help you learn how to synthesize and characterize biodiesel, as well as to distinguish between diesel and biodiesel.
AUS-e-TUTE Members should log-in to access these new resources: http://www.ausetute.com.au

If you are not an AUS-e-TUTE Member, there is a "free-to-view" biodiesel temporarily available at http://www.ausetute.com.au/biodiesel.html for evaluation purposes.

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Heat of Solution

Have you ever wondered why some salts dissolve in water to release heat while others absorb energy?

If so, you should take a look at AUS-e-TUTE's new resources on the Molar Enthalpy of Solution (or Molar Heat of Solution).

AUS-e-TUTE members should log-in to view the new tutorial, game, test, exam and homework checker under the heading Thermochemistry, and the topic heading Heat (enthalpy) of Solution.

Not an AUS-e-TUTE Member?
Currently there is a "free-to-view" tutorial available for evaluation purposes at http://www.ausetute.com.au/heatsolution.html

Find out about the benefits of AUS-e-TUTE membership at
http://www.ausetute.com.au/membership.html

then, when you are ready to start improving your chemistry results, you can join AUS-e-TUTE at
http://www.ausetute.com.au/register.html

Exploding Pool Chemicals

Sydney Morning Herald, Sunday 12^th January 2014, "Sydney man severely injured mixing chlorine for pool"
In summary, the victim of this accident had a backyard pool which had turned green. He had been advised to add 2 kilograms of "chlorine" to his pool to turn it sparkling blue again. He went home, put 2 kg of the "chlorine" granules into a bucket, and added water. Within 30 seconds the mixture exploded. The man was taken to hospital in a critical condition.

Now, for some chemistry....

From the description of the "chlorine" it sounds like it was calcium hypochlorite, Ca(OCl)₂ , a white solid at room temperature and pressure that is commonly sold as "pool chlorine".
When added to water, calcium hypochlorite produces hypochlorous acid, HOCl, and calcium hydroxide, Ca(OH)₂(aq).

Word equation:	calcium hypochlorite	+	water	gives	hypochlorous acid	+	calcium hydroxide
Chemical equation:	Ca(OCl)2	+	2H2O	→	2HOCl	+	Ca(OH)2

Dissolving calcium hypochlorite in water produces energy. The heat (or enthalpy) of solution is about 630 kJ mol^-1
We can now calculate how much energy was released when the man added water to 2 kg of calcium hypochlorite in the bucket.
First we need to calculate how many moles of calcium hypochlorite were in the bucket:
moles (Ca(OCl)₂ ) = mass ÷ molar mass
            and mass (Ca(OCl)₂) = 2 kg = 2 x 1000 = 2,000 g
            and molar mass (Ca(OCl)₂) = 40 + 2(16 + 35.5) = 143 g mol^-1
moles (Ca(OCl)₂ )  = 2000 ÷ 143 ≈ 14 mol
Now,  from the heat (enthalpy) of solution, we know that 1 mole of calcium hypochlorite dissolves in water to produce 630 kJ of energy.
We can calculate how much energy is released when 14 mol of calcium hypochlorite dissolves in water:
energy released = moles x energy in kJ mol^-1
energy released  = 14 x 630 = 8820 kJ
which is equivalent to exploding about 100 g of TNT in the bucket !

Reference:
http://www.smh.com.au/nsw/sydney-man-severely-injured-mixing-chlorine-for-pool-20140111-30nl3.html

Suggested Reading:
Defining Enthalpy Change 
Energy Profiles 
Strength of Acids
Strength of Bases 
pH of Aqueous Salt Solutions 


Suggested Study Questions:

1.  What is the name given to the type of reaction that produced energy?
2.  What name is given to the type of reaction that absorbs energy in order to produce products?
3. Sketch an energy profile diagram for the reaction between calcium hypochlorite and water.
4. Sketch an energy profile diagram for the explosion of TNT.
5. For 2 kg of calcium hypochlorite completely dissolving in water, calculate the moles of calcium hydroxide that would be produced.
6. For 2 kg of calcium hypochlorite dissolving in water, calculate the mass of hypochlorous acid that would be produced.
7. Assume the man used a 30 L of water in a 40 L bucket, what is the concentration of calcium hydroxide expected to be?
8. Hypochlorous acid is considered to be a very weak acid. What does this mean? 
9. Calcium hydroxide is considered to be a strong base. What does this mean?
10. What is the approximate pH of the solution when 2 kg of calcium hypochlorite is dissolved in  30 L of water?
11. What safety precautions do you think pool owners should take when mixing calcium hypochlorite granules with water?
12. Design a safety poster that could be displayed in a pool shop clearly showing the safest way to mix calcium hypochlorite granules with water. 

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.

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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Fracking

Marcellus shale is a massive rock formation that is possibly the largest source of natural gas in the USA. It extends from New York through Pennsylvania, Ohio and West Virginia. Marcellus shale naturally traps metals such as uranium at levels higher than usually found naturally but lower than man-made contamination levels.
Hydraulic fracturing, or fracking, is a process that results in the creation of fractures in rocks in order to tap into oil and natural gas deposits such as those present in Marcellus shale. Millions of gallons of water and chemicals are pumped deep underground to blast through the rocks in order to release the natural gas. University of Buffalo scientists have shown that the metals and the hydrocarbons are chemically bonded, so, the process of drilling to extract the hydrocarbons could force the metals into the soluble phase, enabling them to move around. When the millions of gallons of water used in hydraulic fracturing, or fracking, come back to the surface, it is likely to contain toxic uranium contaminants, potentially polluting streams and other ecosystems and generating hazardous waste.

Reference:
University at Buffalo (2010, October 27). Uranium in groundwater? 'Fracking' mobilizes uranium in marcellus shale. ScienceDaily. Retrieved October 29, 2010, from http://www.sciencedaily.com­ /releases/2010/10/101025172926.htm

Further Reading:
http://www.ausetute.com.au/usehydrc.html
http://www.ausetute.com.au/combusta.html
http://www.ausetute.com.au/chemphys.html
http://www.ausetute.com.au/fuelsdef.html

Study Questions:

1. What is the name and chemical formula of the major constituent of natural gas?
2. What is meant by the term hydrocarbon?
3. Give the names, chemical formulae, and uses for 3 other hydrocarbons.
4. Explain what is meant by the phrase "force the metals into the soluble phase".
5. Is forcing the metals into the soluble phase an example of a chemical or a physical change? Explain your answer.
6. Explain what is meant by a Chemist when he/she refers to a substance as a fuel.
7. Is natural gas defined as a renewable or non-renewable fuel? Explain your answer.
   
8. Natural gas is combusted for use as a fuel. Is this an example of chemical or a physical change? Explain your answer.
9. Write a balanced chemical equation for the complete combustion of the main constituent of natural gas.
10. Of the 3 hydrocarbons you named in question 3, which one would be considered the "best" fuel? Explain your answer.