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

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!

Recovering Gold from e-Waste

 We use electronic devices every day; computers, drones, home security systems, mobile phones, smart speakers, smart watches, etc. If the device stops working, or we want to upgrade to a newer version, we throw away the old device resulting in electronic waste or e-waste. Each of these devices contains a printed circuit board (PCB) and the metal content of each PCB can be as high as 40% by mass. 

Recycling 1 tonne of mobile phones alone could produce more than 130 kg metal, including about 340 g of gold. The value of just the gold in that tonne of rubbish is over $25,000(AUD). Recovering metal from waste electronics and electrical equipment is becoming big business, but what impact does this have on us and our environment?

 Read this edition of AUS-e-NEWS to find out more ...

You can 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

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

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 Aqueous Salt Solutions

If you titrate acetic acid with sodium hydroxide, what is the pH at the equivalence point?

If you dissolve ammonium chloride in water, what is the pH of the solution?

To answer these questions you will have to calculate the pH of an aqueous salt solution!

AUS-e-TUTE has just added new resources to help you do just that!

Members should log-in to use the new tutorial, game, test, drill, worksheet wizard, and problem solving template.

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

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

Alkanol + HX

What happens when you add a concentrated hydrohalic acid, like hydrobromic acid or hydrochloric acid or hydroiodic acid, to an alkanol?
A substitution reaction!
Find out more in AUS-e-TUTE's new tutorial at https://www.ausetute.com.au/alkanolhx.html

AUS-e-TUTE Members should log-in to use the new tutorial, game and test (with worked solutions!).

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 + Carbonate

Carbonate is found in lots of rock-forming minerals as well as in egg shells, corals and oyster shells. It is a major component of limestone, and of marble. 
What happens when carbonate minerals, shells, corals and marble statues meet acids?  
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you write word equations for carbonate and acid chemical reactions. AUS-e-TUTE members should log-in to use these new resources.

A "free-to-view" tutorial is currently available to non-members at

https://www.ausetute.com.au/weacidcarbonate.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

acid + metal

When you add an acid to a metal you expect a chemical reaction to occur in which you produce a salt and hydrogen gas.
Your teacher expects you to be able to write a word equation to describe this chemical reaction.
AUS-e-TUTE has just added a new tutorial, game, test, and exam to help you write word equations for the chemical reaction between an acid and a metal.
AUS-e-TUTE Members should log-in to use these new resources.
If you are not a Member of AUS-e-TUTE, you can access the "free-to-view" tutorial : https://www.ausetute.com.au/weacidmetal.html

pH of Weak Acid After Dilution

What happens to the pH of a solution of weak acid, such as acetic acid, if you dilute it by adding water to it?
How much water would you have to add to 100 mL of 0.20 mol L^-1 acetic acid in order to make a solution with a pH of 3.0 ?
What is the pH of 1 × 10^-11 mol L^-1 acetic acid?
AUS-e-TUTE can help you answer these questions with our new resources.
AUS-TUTE Members should log-in to access the new "pH of Weak Acid After Dilution" tutorial, game and test (with worked solutions).
A "free-to-view" tutorial is currently available for non-members at:
https://www.ausetute.com.au/phdilwa.html

pH after mixing acid and base

If you add enough strong base to a strong acid you can neutralise the solution and its pH will be 7.
But what if you don't add enough base to the acid.
Will the solution be neutral?
Will the pH of the solution be 7?
These are all very good questions which is why AUS-e-TUTE has just added a new tutorial, game, test and exam on this topic.
AUS-e-TUTE Members should log-in to use these resources.

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

Effect of Dilution on pH of Strong Acid Solution

Need to know what the pH of your hydrochloric acid is after you dilute it?
Need to know how much water to add to your hydrochloric acid to make a solution with a particular pH?
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you with this.
AUS-e-TUTE members should log-in to use the new resources.
If you're not an AUS-e-TUTE Member, there is a "free-to-view" tutorial currently available at https://www.ausetute.com.au/phdilsa.html

Name and Formula of Inorganic Acids

There are systematic ways to name inorganic acids, however, for many acids no-one uses these systematic names because the "acid name" for these particular acids has been in use for a very long time. So, IUPAC recognises the "acid name" for a number of acids.
AUS-e-TUTE has just added a new tutorial, game, test, quiz and worksheet wizard, as well as a card game, to help you give the name and molecular formula of these acids. AUS-e-TUTE members should log-in to use these new resources.

If you are not an AUS-e-TUTE member, there is a "free-to-view" tutorial currently available at
https://www.ausetute.com.au/acidnames.html

Don't forgot to download our free "Inorganic Acid Names Card Games" when you visit!
(includes instructions for 3 games and a set of game cards).

Sodium Bicarbonate

One of the single most useful and versatile chemicals I have in my kitchen pantry is a box of sodium bicarbonate, also known as baking soda or bicarbonate of soda.
Read the March 2018 issue of AUS-e-NEWS to find out what makes this compound so special.

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

Gutful of Gas

People can eat interesting things.
In the 1960s in Australia, Leon Samson was eating razor blades to amuse audiences, he even started to eat, slowly, in bits, a car for a bet. A little later, France produced Michel Lotito who was also eating odd things to entertain us, including an airplane between 1978 and 1980.

A razor blade is made out of steel, a particular kind of steel known as razor blade steel. A 2.61 gram razor blade contains between about 13% chromium, 0.6% carbon, and  the rest is iron. Samson would chew up a razor blade and swallow it.

After leaving the mouth, the chewed-up bits of razor blade travel to the stomach. An empty stomach has a volume of about 75 mL but when we eat the volume of the stomach can expand out to about 1 L. Protein-digesting enzymes known as proteases are released into the stomach to help begin the break up of the proteins like you find in meat, fish, eggs and cheese. The optimum pH for these proteases is at about pH 2, so hydrochloric acid is also released into the stomach.

So the small bits of razor blade now find themselves surrounded by hydrochloric acid. Hydrochloric reacts with metals, like the iron in steel, to produce hydrogen gas. Now gases have an interesting property, they expand out to fill the available space. This suggests that eating razor blades might result in a feeling of being bloated. Thankfully, it appears that it takes about 24 hours for the complete reaction between a razor blade and hydrochloric acid in the stomach, plenty of time to remove the gas build-up via burping or, um, farting.

Hydrogen gas is commonly found in our intestines, along with other gases like carbon dioxide, oxygen and nitrogen. Some of these gases get there when we swallow air along with our food and drink, but they also come from chemical reactions inside our bodies. If our bodies are healthy and working well, all the usual gases will be present in the usual concentration, but if there is something wrong, if we are sick, the nature and composition of the gases will change.

Researchers at RMIT University in Melbourne, Australia, have developed and trialed an "ingestible electronic capsule" which is capable of sensing and measuring the gases in the gut like hydrogen, carbon dioxide and oxygen. These capsules offer a new, non-invasive way to monitor the health of our gut. The capsules can be collected after they have been excreted (apparently painlessly).

Reference: 
Kourosh Kalantar-Zadeh, Kyle J. Berean, Nam Ha, Adam F. Chrimes, Kai Xu, Danilla Grando, Jian Zhen Ou, Naresh Pillai, Jos L. Campbell, Robert Brkljača, Kirstin M. Taylor, Rebecca E. Burgell, Chu K. Yao, Stephanie A. Ward, Chris S. McSweeney, Jane G. Muir, Peter R. Gibson. A human pilot trial of ingestible electronic capsules capable of sensing different gases in the gut. Nature Electronics, 2018; 1 (1): 79 DOI: 10.1038/s41928-017-0004-x

Suggested Further Reading 
Experimental Design: http://www.ausetute.com.au/experimentd.html
Name and Formula of Binary Covalent Compounds: http://www.ausetute.com.au/namcform.html
Percentage Composition:  http://www.ausetute.com.au/percentc.html
Mass-moles Calculations: http://www.ausetute.com.au/massmole.html
Molar Gas Volume Calculations: http://www.ausetute.com.au/molarvol.html
Ideal Gas Law Calculations:  http://www.ausetute.com.au/idealgas.html
Metal + Non-Oxidising Acid Reaction: http://www.ausetute.com.au/metalhcl.html
Hydrogen Ion Concentration of Strong Acids: http://www.ausetute.com.au/hstronga.html 
Reaction Calculations: Mass and Moles http://www.ausetute.com.au/molreact.html 

Suggested Study Questions

1.   Design an experiment to determine how long it would take for a razor blade to react completely with the hydrochloric acid in the stomach. Investigate ways to speed up, or, to slow down, this reaction.
2. Give the formula for each of the following:
   • hydrogen gas
   • nitrogen gas
   • oxygen gas
   • carbon dioxide gas
   • hydrochloric acid
3.   Determine the percentage composition of each of the following compounds
   • hydrogen chloride gas
   • carbon dioxide gas
4. From the information in the article, calculate the mass of each of the following elements found in a razor blade:
   • iron
   • chromium
   • carbon
5. Using the information above, calculate the moles of each of the following elements found in a razor blade:
   • iron
   • chromium
   • carbon
6. Calculate the moles of hydrogen gas that occupy the entire volume of a "full" stomach under the following conditions:
   • 0^oC and 100 kPa
   • 25^oC and 100 kPa
   • 37^oC and 100 kPa
7. Write a balanced chemical equation for the reaction between the hydrochloric acid in the stomach and the iron in a razor blade.
8. Calculate the concentration of acid released into the stomach using the information in the article. 
9. Use the balanced chemical equation to determine the volume of hydrogen gas produced when all the iron in a razor blade has reacted with hydrochloric acid.
10. Consider all the information in the article, and the calculations you have performed so far. Explain why it takes 24 hours for a razor blade to be completely digested in the stomach.