Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: anastasiaaleexev on March 17, 2020, 06:23:45 PM
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1. Adding NaNO3 to a HNO3 solution
2. Adding NaCN to a HCN solution
3. Adding NaOH to a NH3 solution
I said that all 3 will increase in pH. Is that correct?
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No.1 I would think again. No.2 is also questionable, regarding built up of a buffer.
No.3 is correct.
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My thinking was that when you add NaNO3 and the NaCN, you will be increasing the concentration of the products (NO3- and CN-), so the equilibrium will shift to the reactants, causing [H+] to decrease.
Since this is incorrect, what would be the explanation for it?
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A lot depends on how much detailed answer you are seeking, you asked in a High School forum, so I assume HS level.
In the case of a strong acid adding salt doesn't matter at all - it is still fully dissociated and (assuming there were no volume/concentration changes) pH doesn't change. In reality it is a bit more complicated.
You are right with 2. though, yes, presence of CN- will shift the dissociation and the pH will go up.
3. is OK as well.
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Got it, thank you! :)