AI and chemistry

 How good are AI generated responses to typical chemistry questions?

No better than the source material used for the answer ... which can include common misconceptions.

One such question is "What is the pH of water?". To a chemist this is a nonsense question (comparable to asking what colour an apple is or what shape a building is) yet it is often asked in school science classrooms around the world. 

I asked ChatGPT "What is the pH of water?" This was the answer ...

The pH of pure water at 25 degrees Celsius (77 degrees Fahrenheit) is considered neutral and is defined as 7. A pH value below 7 indicates acidity, while a pH value above 7 indicates alkalinity. It's important to note that the pH of water can be influenced by dissolved substances, and natural water sources may have varying pH levels due to the presence of minerals and other compounds.

I asked perplexity.ai "What is the pH of water?" This was the answer ...

The pH of water is 7, which is considered neutral. A pH of 7 is neither acidic nor basic. It is important to note that the pH of pure water can change due to the presence of impurities or the absorption of carbon dioxide from the air, which can make it slightly acidic. However, under normal conditions, the pH of pure water is 7, indicating neutrality

2

Surprise, surprise, both answers are inaccurate and riddled with common misconceptions (although, to its credit, perplexity.ai does provide sources, but to its discredit it does not refer to a specific temperature which is critical!). ChatGPT emphasizes "pure water", while perplexity.ai is content with just "water". To a chemist, both terms are the same, "water" is a pure substance. If water has substances dissolved in it it is no longer "water" it is an "aqueous solution". Perplexity.ai's referral to "normal conditions" is baffling, perhaps it refers to standard conditions for aqueous solutions? After these issues, both AIs seem to perpetuate the misconception that acidity, basicity (alkalinity) and neutrality are defined by a pH value. This is not true. They are two entirely different concepts (although both are based on an Arrhenius description of aqueous solutions). pH is a measure of aqueous hydrogen ion concentration, independent of whether the aqueous solution has been designated acidic, basic or neutral. Acidic, basic, neutral are terms to describe a the relative amounts of hydrogen ions and hydroxide ions in an aqueous solution.

So, let's start by talking about the neutrality of "pure water". Pure water is always neutral (regardless of its pH). This is because the concentration of acidic protons in the water, H⁺(aq) or H₃O⁺(aq), is always equal to the concentration of basic hydroxide ions in the water, OH^-(aq), that is [H⁺(aq)] = [OH^-(aq)]

An acidic aqueous solution is one in which the concentration of acidic protons is greater than the concentration of basic hydroxide ions, that is, [H⁺(aq)] > [OH^-(aq)]

A basic aqueous solution is one in which the concentration of acidic protons is less than the concentration of basic hydroxide ions, that is, [H⁺(aq)] < [OH^-(aq)] 

So "pure water" is always neutral, but what is its pH? pH is a measure of the concentration of aqueous hydrogen ions in solution, the greater the concentration of hydrogen ions in aqueous solution, the lower the pH. The concentration of these hydrogen ions is very much dependent on the water temperature. The pH of pure water at 10^oC is approximately 7.27 but the water is still described as neutral because [H⁺(aq)] = [OH^-(aq)]. The pH of pure water at 50^oC is about 6.63 but the water is still neutral because [H⁺(aq)] = [OH^-(aq)].

 The pH of water at 25^oC is approximately 7 and is based, NOT on it being defined this way, but on a calculation of the hydrogen ion concentration of water at this temperature.

So, what happens to pH if other substances are dissolved in water to form aqueous solutions at 25^oC? Using an Arrhenius definition of acids and bases (and a pH of 7 which has 1 significant figure but even that digit is uncertain), if an aqueous solution has pH < 7  at 25^oC it could be described as acidic, but if the temperature is greater than 25^oC the solution may be neutral, it may even be basic, we simply do not have enough information to decide. Similarly, If an aqueous solution has pH > 7  at 25^oC it could be described as basic, but if the temperature is less than 25^oC it is not a justifiable conclusion.

It is important to note that if there are dissolved "substances", including "impurities", "minerals" or "carbon dioxide", then the "water" is not "pure water", it is an aqueous solution, and the AI discussions are not relevant. Furthermore, some solutes dissolve in water at 25^oC and increase its pH  (aqueous solution of sodium hydroxide), some decrease its pH  (aqueous solution of hydrogen chloride), and some may have no effect at all on its pH (aqueous solution of sodium chloride).

There is no simple, correct answer for the question "What is the pH of water?". The question does not contain enough information in order for it to be answered. IF the AIs simply stated that the pH of water at 25^oC is approximately 7, that would be a pretty good response, however, by providing additional information in the answer they are repeating, and encouraging, common misconceptions about the nature of "pure water", "pH", "acidity", "basicity" (or "alkalinity") and "neutrality". 

For a discussion on why pure water is always neutral and why its pH varies, see https://www.ausetute.com.au/kw.html

For a discussion on what determines whether an aqueous solution is acidic, basic or neutral, see https://www.ausetute.com.au/abneutral.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!

Arrhenius Acids and Bases

What is an acid?

What is a base?

These are both good questions and there is no simple answer.

It all depends on how you decide to define the terms "acid" and "base".

More than 100 years ago, a clever chemist by the name of Arrhenius proposed the first really useful definitions of acids and bases and AUS-e-TUTE has just added a new tutorial, game, test and exam (with worked solutions!), and even some flash cards o help you understand and apply the Arrhenius definition of an acid and of a base.

Not an AUS-e-TUTE Member? You can go to a free-to-view tutorial at 

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

Hydrolysis of Acids and Bases

If you want to find the value of the acid dissociation constant for a weak acid you look up tables of values. For example, the value of K_a for acetic acid (ethanoic acid) is always tabulated.
But what if you want the value of a base dissociation constant?  What if you want the value of K_b for the acetate ion (ethanoate ion)? You won't find this value in a table, you'll have to know how to calculate it!

AUS-e-TUTE has just added new resources to help you understand and apply the concept of acid and base hydrolysis including calculations. AUS-e-TUTE Members should log-in to access the new tutorial, game, test, exam (with worked solutions), and teacher members can access the worksheet wizard to make printable worksheets and quizzes (with answers).

If you are not an AUS-e-TUTE Member, the "free-to-view" tutorial is currently available at

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

acid + base

When an acid and a base are mixed together they react to produce a salt and water.
The general word equation for this type of acid-base reaction is:

acid + base → salt + water

But can you write the word equation for the reaction between a specific acid, for example hydrochloric acid , and specific base, say sodium hydroxide?

AUS-e-TUTE is here to help!

We've just added new learning resources; a tutorial, game, test and exam to help our members write acid + base word equations. We even have a worksheet wizard that lets teachers make their own printable worksheet or quiz on this topic.

You can join AUS-e-TUTE today at https://www.ausetute.com.au/register.html

If you would like to a view a read-only tutorial for free, you can at https://www.ausetute.com.au/weacidbase.html

What is the pH of a Strong Base After You Dilute It?

The problem with strong bases like sodium hydroxide and potassium hydroxide are that they absorb moisture from the air making it difficult to accurately weigh them. So we rely heavily on obtaining an accurately known concentration for an aqueous solution of a strong base (using titration techniques for example) and then diluting this stock solution to produce new, dilute solutions of known concentration and pH.
When you dilute an aqueous solution of a strong base :

• hydroxide ion concentration decreases (towards 10^-7 M)
• pOH increases (towards 7)
• hydrogen ion concentration increases (towards 10^-7 M)
• pH decreases (towards 7)

Visit AUS-e-TUTE's new tutorial to understand why, then log-in to the Members ONLY area to play the game, answer test and exam questions (which give you instant feedback), take the quiz, or, just for teachers, you could make a printable worksheet or quiz.

AlP Rat Poison

Dozens of mysterious sealed silver canisters containing aluminium phosphide have washed up on Australian beaches between 2012 and 2015. The Australian Maritime Safety Authority (AMSA) suspects all the canisters have come from the same ship which dumped or lost its cargo in the Pacific Ocean. Aluminium phosphide is used as a fumigant to poison rats on ships.

When solid aluminium phosphide, AlP, is exposed to water, it releases highly toxic phosphine gas, PH₃, which smells like rotting fish. The chemical reaction can be represented by the balanced chemical equation shown below:
AlP_(s) + 3H₂O_(l) → PH_3(g) + Al(OH)_3(aq)

This is a proton-transfer reaction in which water is acting as Brønsted-Lowry acid by donating a proton to phosphorus. Phosphorus is therefore acting as a Brønsted-Lowry base by accepting a proton from water. Aluminium phosphide will react with acids according to the following chemical
AlP_(s) + 3H⁺_(aq) → PH_3(g) + Al³⁺_(aq)

These reactions make aluminium phosphide a good choice for ridding a ship of rats.
Firstly, as a solid, AlP can easily be stored as pellets in air-tight, water-tight, containers until it is ready to be used. When required, the pellets can be scattered in the effected area . In the humid air aboard ship, the AlP will start reacting to produce toxic phosphine gas, that is, the area will be fumigated. But it is also possible to entice rats to eat AlP pellets mixed with food, in which case it will act as pesticide, because on entering the acidic stomach of the rat, it will produce the toxic phosphine.

Aluminium phosphide is  a very effective way to get ride of rats, so much so, that is widely used in agriculture to remove rats from grain silos.

References:
"Toxic canisters washing up on Australian beaches pose serious health risk"
 http://www.smh.com.au/environment/toxic-canisters-washing-up-on-australian-beaches-pose-serious-health-risk-20150917-gjp5se.html

"Controlling rabbits with aluminium phosphide tablets"
 http://agriculture.vic.gov.au/agriculture/farm-management/chemical-use/publications/chemical-industry-news/chemical-industry-news-no.-75-summer-autumn-2013

"Phosphine fumigation"
https://www.worksafe.qld.gov.au/injury-prevention-safety/hazardous-chemicals/specific-hazardous-chemicals/phosphine-fumigation

Further Reading
Definition of Acids and Bases
Proton-transfer Reactions
Mass-mole Calculations
Molar Volume of Gases

Suggested Study Questions:

1. The symbols of some elements are listed below. Name each element.
   • Al
   • P
   • H
   • O
   • K
   • He
   • At
2. Calculate the amount of aluminium phosphide in moles given the masses of AlP given below:
   • 10 g
   • 10 kg
   • 10 mg
   • 10 μg
3. Calculate the moles of phosphine gas produced when each mass of AlP below reacts with excess water in a ship's hull:
   • 10 g
   • 10 kg
   • 10 mg
   • 10 μg
4. Based on your answers to question 3 above, calculate the mass of phosphine produced for each mass of AlP used.
5. Your ship is sailing towards eastern Australia and has just crossed the Tropic of Capricorn. You have been asked to estimate the volume of phosphine gas that will be produced when you release AlP pellets into the ships hold. Which molar gas volume will you use; 22.71 L or 24.79 L ? Explain your answer.
6. Rats are currently infesting a small part of your ship, about 150 m³. How much solid AlP would be required to fumigate this area, but not leave any AlP residue left over?
7. The Cook has already tried to fumigate the pantry and is sure there is a silver canister around that still contains some AlP, it could be in the pile of empty canisters, or, it could be in the pile of full canisters. No-one wants to kill themselves by opening the canisters to find out, so can you suggest a method that could be used on board ship to determine how much AlP is present in each canister.
8. Explain why the reaction between aluminium phosphide and water is described as a proton-transfer reaction and not as a redox reaction.
9. Explain why, even though aluminium phosphide and phosphine are toxic, it is considered safe to use these to fumigate silos containing grain which will be eaten by humans.
10. The silver canisters that have washed up on Australian beaches have no labels, presumably these have come off while they were in the ocean. You have been asked to design new labels for the canisters. The labels must include suitable safety and handling information.

Sulfuric Acid - Sodium Hydroxide Titrations

Why does a titration of sulfuric acid using sodium hydroxide have only one equivalence point?
Why isn't the pH 7 at the equivalence point?

These are both excellent questions.

So, we've written a set of resources to help you understand!

AUS-e-TUTE Members should log-in and go to the new tutorial at:
http://www.ausetute.com.au/members/titrh2so4.html
and you can follow the links to the game and test from this page.

Not an AUS-e-TUTE member?
Part of this tutorial is currently available free to non-members for evaluation purposes at
http://ausetute.com.au/titrh2so4.html

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 AUS-e-TUTE Resources

AUS-e-TUTE has just added new resources on the strength of conjugate acids and bases, as well as proton-transfer reactions.

The new resources will be found under the Acids and Bases Topic Heading.

http://www.ausetute.com.au

Calculations for Strong Bases

AUS-e-TUTE has just added new resources!
As part of the update of our "Acids and Bases" topic, tutorials, games, tests, and exams have been added for the following:

• pOH Concepts
• Strength of Bases
• Calculating the pOH of Strong Bases (aqueous solutions)
• Calculating the Hydroxide Ion Concentration of Strong Bases (aqueous solutions)
• Calculating the pH of Strong Bases (aqueous solutions)
• Calculating the Hydrogen Ion Concentration of Strong Bases (aqueous solutions)

pH of the Manning River

"A POISONOUS plume of acid 'comparable to car batteries' is forming in the Manning River, near Taree in northern NSW, researchers from the University of NSW say." reports Ben Cubby in his article "Acid plume poisons river after floods"  in the Sydney Morning Herald, Thursday 28^th February 2013.
Let's take a look at the chemistry behind the story.
Firstly, Taree, a town located about 3 hours north of Sydney, is surrounded by farm land, land reclaimed from the wetlands. The sulfate ion, SO₄^2-, is commonly found in fertilizers used in commercial farming. Recent rain, and flooding, has concentrated these acidic sulfates in the river.

A little later in the story we find that "Tests carried out by the university's water research laboratory show alarming amounts of acid, with a pH level of two - compared with a normal level of seven - meaning the Manning River water is roughly as acidic as lemon juice."
Chemistry students would realize that there are many factors that can effect the pH of river water, for example, if the river runs through limestone rocks the pH of the water will increase, but if the river runs through areas of peat the pH of the water will decrease.
The pH of river water typically lies within the range of about 6.5 to 8.5.  Water with a low pH is said to be acidic, water with a high pH is said to be basic or alkaline. Most organisms, with the exception of some bacteria, can not live in water with a pH less than 6.5. Similarly, a pH greater than 8.5 also presents problems for the survival of most organisms in rivers.
The juice of a lemon often has a pH of about 2, and the vinegar you buy from the shop will also have a pH around 2. Both lemon juice and vinegar are acidic substances.
On the other hand, oven cleaner has a pH of about 13 and soapy water has a pH of about 12. Both oven cleaner and soapy water are basic solutions (or alkaline solutions).

Is river water with a pH of 2 "comparable to car batteries" as claimed in the story?
Lead-acid batteries, such as those found in cars, contain sulfuric acid, H₂SO₄. Sulfuric acid is a strong acid that undergoes dissociation in water so that an aqueous solution of sulfuric acid contains both hydrogen ions, H⁺, and sulfate ions, SO₄^2-. The acidic river water will contain both hydrogen ions, H⁺, and sulfate ions, SO₄^2-, if sulfate fertilizers have been used on the land where the river runs, so the acid in the car's lead-acid battery and the river water are comparable in that they contain the same ions.
The concentration of sulfuric acid in the lead-battery will usually be between 4 and 5 mol L^-1 (let's just assume its 4.5 mol L^-1 ).
If we assume the complete dissociation of sulfuric acid:
H₂SO₄ → 2H⁺ + SO₄^2-
Then the concentration of hydrogen ions, H⁺, in solution is 2 times the concentration of the sulfuric acid:
[H⁺] = 2[H₂SO₄ ] = 2 x 4.5 = 9.0 mol L^-1
We can calculate the pH of the battery acid, since pH = -log₁₀[H⁺] = -log₁₀[9.0] = -0.95
Battery acid is very, very acidic!
While you might be very happy to put vinegar on your chips (pH~2) and eat them, you  should most definitely NEVER put battery acid on your chips and eat them!

Reference:

 http://www.smh.com.au/environment/conservation/acid-plume-poisons-river-after-floods-20130227-2f6bh.html#ixzz2MA2XQ5AJ

Further Reading:
Calculating pH

Suggested Study Questions:

1. Draw up a table with two headings; acid and base. Place each of the following substances in  the correct column in the table : orange juice (pH =3), baking soda (pH = 9), milk (pH =6), tomato juice (pH =4),  drain cleaner (pH =14), black coffee (pH=5).
2. Calculate the concentration of hydrogen ions in each of the substances in the table, in mol/L
3. Assume a drinking glass has a total value of 250 mL, and that a "full glass" of a drink is actually only 225 mL. Calculate the moles of hydrogen ions found in a "full glass" of
   • orange juice
   • milk
   • black coffee
4. Consider 225 mL of the river water with a pH =2. Calculate the moles of hydrogen ions present.
5. Imagine you took 25 mL of orange juice (pH=3) and diluted it with water to a volume of 500 mL. 
   • Calculate the concentration of hydrogen ions in the diluted solution.
   • Calculate the pH of the diluted solution.
6.  Sometimes cooks heat ingredients to "release their flavour". Acids, like vinegar, tend to have a sour taste. A cook has 200 mL of vinegar (pH=2.2)  in a pan.
   • Calculate the concentration of hydrogen ions present in the solution.
   • On very gentle heating, the volume of the vinegar solution is reduced until it is only 50 mL. Calculate the pH of this concentrated solution.
7. We could prepare a solution of sulfuric acid with a pH of 2 using the acid out of the car's lead-acid battery.
   • Calculate the concentration of hydrogen ions present in 4.5 mol L^-1 sulfuric acid.
   • Calculate the concentration of hydrogen ions present in sulfuric acid with a pH of 2.
   • If you had 10 mL of battery acid, what volume of water would you have to add in order to prepare a sulfuric acid solution with a pH of 2?
8. Imagine the a dam with a volume of 250,000ML and a pH=2. How much water would have to be added to the dam in order for the dam to have a pH=7 ?

Neutral pH?

We hear this term a lot, often in advertising. But what does it mean?

From a Chemist's point of view, there are two different concepts involved in this seemingly harmless "neutral pH" expression. These two different concepts are:

• neutral
• pH

Let's take a look at the Chemist's definition of neutral first.
A solution is neutral if the concentration of hydrogen ions, [H⁺], is equal to the concentration of hydroxide ions, [OH^-].
Chemists often use square brackets to denote concentration, the concentration of  hydrogen ions can be written as [H⁺] and the concentration of hydroxide ions can be written as [OH^-].
So, for a neutral solution:

[H⁺] = [OH^-] = neutral solution 

Pure water is an excellent example of a neutral substance.

Some of the water molecules, actually very few of them, dissociate to form hydrogen ions and hydroxide ions:

H2O

H+ + OH-

Every time a water molecule dissociates, it produces one hydrogen ion, H⁺, and one hydroxide ion, OH^-, so that the concentration of hydrogen ions is always the same as the concentration of hydroxide ions.
Therefore, pure water is always neutral!

The pH of a solution is a measure of the hydrogen ion concentration in the solution. pH can be defined as:

pH = -log₁₀[H⁺]

This equation can be used to calculate the pH of our neutral water, but only if we know the concentration of  hydrogen ions in the water.

The concentration of hydrogen ions in water is not constant!

The concentration of hydrogen ions in water depends on the temperature of the water!
The dissociation of water molecules requires energy:

H2O + energy

H+ + OH-

If you put more energy into the system by heating it, then more water molecules dissociate, the concentration of hydrogen ions increases and the concentration of hydroxide ions also increases.
If you take energy away from the system by cooling it, then fewer water molecules dissociate, the concentration of hydrogen ions decreases and the concentration of hydroxide ions also decreases.
If we were to measure the concentration of hydrogen ions in pure water at various temperatures, we would find the following values:

Water temperature	[H+] x 10−7 M	pH
0°C	0.32	7.50
10°C	0.55	7.26
18°C	0.84	7.08
25°C	1.10	6.96
30°C	1.34	6.87
50°C	2.82	6.55
60°C	3.55	6.46
70°C	4.60	6.34
80°C	5.92	6.23
90°C	7.28	6.14
100°C	8.54	6.07

So what is the pH of water?
The pH of water is dependent on the temperature of the water.
Water is neutral for every value of pH because the concentration of hydrogen ions is always equal to the concentration of the hydroxide ions.
We can ONLY talk about the pH of water IF we state the temperature of the water.
For example, we can talk about water having a pH of approximately 7 at 25^oC, or we could say that the pH of water is approximately 6 at 100^oC.
Pure water is always neutral.
Pure water is neutral at 25^oC.
Pure water is neutral at 100^oC.

As Chemistry students, what we can't say is that water has a pH of 7, or that a neutral aqueous solution has a particular pH, unless we state the temperature of the system.

Further Reading:
Definitions of Acids and Bases
pH
Dissociation Constant for Water

Suggested Study Questions:

1. Plot a graph of temperature versus concentration of hydrogen ions in water. Describe the shape of the line, and write a generalization that links hydrogen ion concentration and temperature.
2. Plot a graph of temperature versus pH of water. Describe the shape of the line and write a generalization linking the  temperature of water and its pH.
3. Use your graph to find the pH of water at:
   • 12^oC
   • 22^oC
   • 32^oC
4. Construct a table giving the concentration of hydroxide ions in water at each of the temperatures shown above.
5. Plot a graph of temperature versus concentration of hydroxide ions in water. Describe the shape of the line, and write a generalization linking hydroxide ion concentration in water and temperature.
6. Use your graph to find the concentration of hydroxide ions in water at:
   • 12^oC
   • 22^oC
   • 32^oC
7. Explain why water is neutral at all temperatures.
8. Explain why the pH of water varies with temperature.

Bath Bombs

Fizzy bath bombs, the scented balls you place in your bath, are an example of a chemical reaction between an acid and a carbonate.
Below is a simple recipe for making your own bath bombs.

Equipment	Procedure
mixing bowl jar waxed paper 2 tablespoons citric acid 1/4 cup sodium bicarbonate 1/4 teaspoon fragrant oil (eg lavender oil) 3 tablespoons vegetable oil (eg olive oil)	1. Mix sodium bicarbonate and citric acid together in the mixing bowl. 2. Mix fragrant oil and vegetable oil together in the jar. 3. Slowly add contents of jar to mixing bowl while stirring. 4. Form small balls of mixture and place on waxed paper. 5. Allow balls to dry for 1 or 2 days before storing. 6. Add a ball to your bath water and enjoy!

When you drop your bath bomb into water, the process of dissolving the bath bomb allows the sodium bicarbonate and citric acid to react to produce soluble sodium citrate, water and carbon dioxide gas. The bubbles of carbon dioxide given off during the reaction is why the bath bomb fizzes in the water.

The vegetable oil is not soluble in water, so as the sodium bicarbonate and citric acid react, vegetable oil is released into the water forming a thin layer on your skin which can help "moisturize" it. At the same time, the fragrant oil, which is also insoluble in water, is released, so you can smell the scent.

Further Reading
Definitions and Properties of Acids and Bases
Reaction Calculations: Mass and Moles
Limiting Reagents and Reactants in Excess

Suggested Study Questions

1. Sodium bicarbonate is also known as sodium hydrogen carbonate, baking soda, bread soda and cooking soda. Write the chemical formula for sodium bicarbonate.
2. Write a word equation for the reaction between citric acid and sodium bicarbonate.
3. A balanced chemical equation for the reaction between citric acid and sodium bicarbonate is :
   C₅H₇O₅COOH + NaHCO₃ → C₅H₇O₅COO^-Na⁺ + H₂O + CO₂
   Name each of the following compounds:
   • NaHCO₃
   • C₅H₇O₅COOH
   • C₅H₇O₅COO^-Na⁺
   • CO₂
   • H₂O
   
   
4. Write a chemical equation to show citric acid acting as a Bronsted-Lowry acid.
5. Sodium bicarbonate is amphiprotic.Write a chemical equation to show sodium bicarbonate
   • accepting a proton
   • donating a proton.
6. In the reaction between citric acid and sodium bicarbonate, is sodium bicarbonate acting as an acid or a base? Explain your answer. 
7. For the bicarbonate ion, give the formula for its
   • conjugate base
   • conjugate acid 
8. The density of citric acid is about 1.5 g/mL. If a tablespoon has a volume of 15 mL, what mass of citric acid was used in preparing the bath bomb? 
9. Sodium bicarbonate has a density of about 2.2 g/mL and there are 16 tablespoons in 1 cup. What mass of sodium bicarbonate was used to make the bath bomb?
10. For the reaction between citric acid and sodium bicarbonate given the quantities used in the procedure provided above, which reactant is
    • the limiting reagent
    • the reactant in excess
11. Calculate the mass of carbon dioxide you would expect to be released during the reaction between citric acid and sodium bicarbonate as described in the above procedure. 
12. Assuming a temperature of 25^oC and a pressure of 100 kPa, what volume of carbon dioxide gas would be released using the data above? 
13. If the amount of sodium bicarbonate used to make the bath bombs as described above were doubled, what effect would that have on the amount of carbon dioxide produced when the bombs were placed in water?
14. Write an aim for the experiment described above.

Restricting Chemical Sales

Police in Western Australia want to restrict stores selling some chemicals in a bid to "smash" clandestine drug laboratories according to a story in the Courier Mail today.
The list of chemicals being targeted includes drain cleaners, battery acid, and common lawn fertilizers.

Drain cleaners often contain sodium hydroxide, also known as caustic soda or lye. Sodium hydroxide, a white solid at room temperature, is a strong base that can cause chemical burns.
When sodium hydroxide is added to a blocked drain it dissolves in the water in the pipe and releases heat. This heat can melt the grease blocking the pipe. The sodium hydroxide also reacts with some of the fat in the pipe to form soap. This soap helps remove the grease blocking the drain.

Lead-acid batteries that are typically found in cars contain sulfuric acid, also known as vitriol. It is a strong acid that used in concentrations of around 30% w/w in battery acid. When sulfuric acid dissolves in water, heat is given off. Sulfuric acid can be neutralized by sodium hydroxide with the products of the reaction being water and sodium sulfate.

High-nitrogen content fertilizers can contain ammonium nitrate which is itself a white solid at room temperature and pressure. When ammonium nitrate dissolves in water it absorbs energy from the surroundings. Ammonium nitrate reacts with sodium hydroxide to produce ammonia gas, water and sodium nitrate.
Ammonia is a colourless gas with a pungent odour at room temperature and pressure. "Household ammonia", sold as a cleaning product for ovens, glass, porcelain and stainless steel, is a solution of ammonia in water. The concentration of this basic solution varies from 5% w/w to 10% w/w.
Ammonia is used to make many pharmaceuticals.

Reference
http://www.couriermail.com.au/news/national/police-bid-to-restrict-chemical-sales/story-e6freooo-1226077611068

Further Reading
Naming Ionic Compounds
Writing Ionic Formula
Definitions and Properties of Acids and Bases
Enthalpy Change
Concentration: Percent by Mass
Concentration: Molarity


Study Questions

1. Give the chemical formula for the following compounds:
   
   • sodium hydroxide
   • sulfuric acid
   • sodium sulfate
   • ammonia
   • ammonium nitrate
   • sodium nitrate
   • water
2. Draw up a table with the headings, acidic, basic, neutral. Place the compounds listed above in the appropriate places in the table.
3. Draw up a table with the headings ionic and covalent. Place the compounds listed in question 1 in the appropriate places in the table.
4. Define the terms exothermic and endothermic.
5. Write an equation to show sodium hydroxide dissolving in water. Include the energy term. Is this reaction exothermic or endothermic?
6. Write an equation to show sulfuric acid dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
7. Write an equation to show ammonium nitrate dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
8. Convert the following percent by mass concentrations to concentrations in mol/L
   
   • 30% w/w aqueous sulfuric acid solution
     
   • 5% w/w aqueous ammonia solution
   • 10% w/w aqueous ammonia solution
9. Write balanced chemical equations for each of the following:
   
   • the neutralization of sulfuric acid by sodium hydroxide in aqueous solution
   • ammonium nitrate reacts with sodium hydroxide in solution
10. Write an equation to show how sodium hydroxide can react with a fat to produce soap.
11. Explain how soap can clean up built up grease in your drain.
12. A student found a container of solution in the family's garage. it is believed to be either household cleaner or battery acid. Describe tests that you could conduct in order to determine what solution is in the container. What safety precautions would you take when conducting these tests?