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Topic: Which one of these salts makes a chemical reaction with vinegar?  (Read 289 times)

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Offline INeedSerotonin

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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

Offline Borek

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #1 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?
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Offline jeffmoonchop

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #2 on: July 15, 2019, 06:22:57 PM »
What is the pH of each solution before you add vinegar?

Offline INeedSerotonin

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #3 on: July 16, 2019, 08:36:40 AM »
Do you know what a spectator is?

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

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

Offline INeedSerotonin

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #4 on: July 16, 2019, 08:39:40 AM »
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?

Offline Borek

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #5 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.
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Offline INeedSerotonin

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #6 on: July 16, 2019, 09:57:35 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?

Offline Borek

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Re: Which one of these salts makes a chemical reaction with vinegar?
« Reply #7 on: July 17, 2019, 03:13:44 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?
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