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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: INeedSerotonin on July 15, 2019, 06:08:07 PM

Title: Which one of these salts makes a chemical reaction with vinegar?
Post by: INeedSerotonin on July 15, 2019, 06:08:07 PM
Hello

I was doing chemistry exercises, and I found this one that mentioned three salts: NH4NO3, Na2CO3, and NaNO3. It proceeds to mention that each of these is in its own container in an aqueous solution.

Then it asks, "which one of these can react with vinegar?"

I know the answer is Na2CO3, but I don't know why the others can't make a chemical reaction with vinegar. Can anybody here explain it to me or give me a hint?

Thank you
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: Borek on July 15, 2019, 06:19:55 PM
Do you know what a spectator is?

Can you think of any reaction with acetic acid in which any of the ions present in the two other solutions could take place?
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: jeffmoonchop on July 15, 2019, 06:22:57 PM
What is the pH of each solution before you add vinegar?
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: INeedSerotonin on July 16, 2019, 08:36:40 AM
Quote from: Borek on July 15, 2019, 06:19:55 PM
Do you know what a spectator is?

I didn't, but now I know. How can I resolve this exercise with this knowledge?

Quote from: Borek on July 15, 2019, 06:19:55 PM
Can you think of any reaction with acetic acid in which any of the ions present in the two other solutions could take place?

Yes!

CH3COOH + NH4+NO3- ---> CH3COO(NH4)+ + HNO3

And

CH3COOH + Na+NO3- ---> CH3COO(Na)+ + HNO3
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: INeedSerotonin on July 16, 2019, 08:39:40 AM
Quote from: jeffmoonchop on July 15, 2019, 06:22:57 PM
What is the pH of each solution before you add vinegar?

I believe that, in pH order, it goes like NH4NO3, NaNO3, Na2CO3. So Na2CO3 acts like a basic salt, and thus it should react with vinegar (an acid). NH4OH is a weak base, and HNO3 is a strong acid; NaOH is a strong base, and HNO3 is a strong acid; and NaOH is a strong base, and H2CO3 is a weak acid.

This is how the answer made sense to me, but I don't know how to calculate the exact values of pH from such little information. Shouldn't the others react with vinegar too?
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: Borek on July 16, 2019, 09:32:14 AM
Quote
Quote
Can you think of any reaction with acetic acid in which any of the ions present in the two other solutions could take place?

Yes!

CH3COOH + NH4+NO3- ---> CH3COO(NH4)+ + HNO3

And

CH3COOH + Na+NO3- ---> CH3COO(Na)+ + HNO3

Write them in ionic form, cancel out spectators.
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: INeedSerotonin on July 16, 2019, 09:57:35 AM
Quote from: Borek on July 16, 2019, 09:32:14 AM
Quote
Quote
Can you think of any reaction with acetic acid in which any of the ions present in the two other solutions could take place?

Yes!

CH3COOH + NH4+NO3- ---> CH3COO(NH4)+ + HNO3

And

CH3COOH + Na+NO3- ---> CH3COO(Na)+ + HNO3

Write them in ionic form, cancel out spectators.

They all have cancelled each other! Is there a name to this phenomenon? Does this mean that no HNO3 is actually formed?
Title: Re: Which one of these salts makes a chemical reaction with vinegar?
Post by: Borek on July 17, 2019, 03:13:44 AM
Quote from: INeedSerotonin on July 16, 2019, 09:57:35 AM
They all have cancelled each other! Is there a name to this phenomenon?

Yes, it is called "no reaction" ;)

Quote
Does this mean that no HNO3 is actually formed?

This is a bit more complicated.

Please note that to some extent every solution containing both H+ and NO3- is a solution of the nitric acid. If you prepare 1M solution of HNO3 there is no doubt this is a nitric acid solution. Now add 1 M NaCl. Would you agree it is still a nitric acid solution, just with some NaCl added? Now prepare 1 M solution of HCl and add 1 M NaNO3. Can you distinguish it from the previous solution? Is it a hydrochloric acid solution with NaNO3 added, or a nitric acid solution with NaCl added?

Or perhaps it actually doesn't matter how we call it as long as we just list all the ions present?