Chemistry Question – Acids, Bases & Salts

06 Apr

Posted by: sean in: Chemistry Notes & Tips

This is an application question on Acids, Bases & Salts that was sent to sean@simplechemconcepts.com by a local “Student X” to be shared and discussed with “chemists” in the world. Student X has also contributed her ideas and answers with the question. Do leave some comments for Student X and other students reading this Chemistry Blogsite. Btw, i need to empahsize that it is ok to make mistakes now as we discussed questions. It is definitely better to make mistakes now as compared to mistakes during your examinations.

Question:
Use your knowledge of the nature of acids, bases and salts to explain the following observations or practices.

Among other ingredients, cake mixes contain a solid mixture of tartaric acid and sodium hydrogen carbonate. The mixture can only “rise” if water is added.

Student X’s suggested answer:
“Tartaric acid reacts with sodium hydrogen carbonate to give metal salt + water + carbon dioxide. Carbon dioxide released is trapped in the mixture, thus causing the mixture to “rise”.”

PS: Check out “Comments” below for suggested answers.

What's Next?

Digg it

Stumble it

Twitter it

5 Responses

Sean Chua
16|Apr|2008 1

Hi. I am the founder & master trainer of SimpleChemConcepts.com.

Your concept is correct. However, you are not answering to the question directly.
Main question is asking you why the cake will only rise if “water” is added. Thus,
the focus is on the word “water” itself.

My suggested answer will be:
In the cake mixture, there is sodium hydrogen carbonate and solid tartaric acid.
However, the solid tartaric acid has no acidic properties and will not react with the
carbonates. When water is added to the cake micture, the tartaric acid gains its
acidic properties and react with the carbonates to form salt + water + carbon
dioxide. The carbon dioxide produced will caused the rise of the cake.

Hope this helps,
Sean
http://www.SimpleChemConcepts.com

Reply
JO.
26|May|2008 2

hi.
i have an inquiry about this question regarding the acids and bases that i hope you can help me with.

in the case that there is a weak acid (ethanoic acid) of higher concentration than the strong acid (sulphuric acid) of weaker concentration, and they are both made to react with calcium carbonate. which acid would be the one which produces more carbon dioxide?

thank you.

Reply
Helen
29|May|2008 3

Hey … how r u ?

I would like to ask you a question about a diagram of strong acids and weak acids which you had posted on the website … the diagram depics sulphurous acid as being a strong acid ……

I used to think that sulphurous acid was known to be a weak acid and thus a weak electrolyte …

so is it not that way ?

by the way .. thanks alot for the great website.. you are doing a great job here

thanks

Reply
sean
07|Jun|2008 4

Hi Jo,

Comparing:

A) Strong Acid (but with weak concentration)
B) Weak Acid (but with high concentration)

I will go for Answer A.

Reason is because strong acid has 100% dissociation of H+ ions. Even when its
concentration is low, there are enough H+ ions around.

If you look at weak acid like ethanoic acid, no matter how migh you concentration
is, the number of H+ ions is still very low. This is because for weak acid, there is
only partial dissociation of acid to give small number of H+ ions.

There is mention in most text books that for ethanoic acid, only 4% of H+ ions are
dissociated. Most remain intact.

Hope this is clear.

Reply
sean
07|Jun|2008 5

Hi Helen,

I am doing fine. Will be conducting a 40hrs Intensive Chemistry Revision Bootcamp
for Singapore students in a weeks time. Been very busy to make sure this Bootcamp
will provide this special group of students with the tools & strategies for them to
score that grade that they truly deserve.

Back to your question, 1st i would want to differentiate:
Sulphuric Acid H2SO4
Sulphrous Acid H2SO3
–> They are 2 different acids but have one similarity, they are STRONG ACID.

WEAK ACID is usually fruit/organic acid such as acetic acid, ethanoic acid, etc.

Hope you will find this information useful to u.

Reply