HNO3 & CH3COONa: A Buffer Solution That Doesn't Follow the Rules

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Discussion Overview

The discussion centers on the potential for HNO3 and CH3COONa to function as a buffer solution, despite not fitting traditional criteria for buffer systems. Participants explore the chemical interactions and equilibrium reactions involved, questioning the roles of the resulting compounds.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that HNO3 and CH3COONa do not fit the classic definitions of buffer solutions, which typically involve weak acids and their salts or strong acids and bases.
  • Another participant suggests considering the compounds and ions present in the solution and the equilibrium reactions that occur.
  • A participant proposes a reaction between HNO3 and CH3COONa, leading to the formation of NaNO3 and CH3COOH, questioning whether CH3COOH and CH3COONa are responsible for buffering.
  • There is a discussion about the nature of nitric acid and whether it can contribute to buffering capacity.
  • Concerns are raised about the presence of NaNO3 and its potential effect on the buffer system, with one participant asserting that it only alters the ionic strength of the solution.

Areas of Agreement / Disagreement

Participants express differing views on whether HNO3 and CH3COONa can effectively act as a buffer. Some acknowledge the formation of CH3COOH and CH3COONa as a buffer, while others question the role of NaNO3 and the nature of nitric acid in this context. The discussion remains unresolved regarding the overall buffering capacity of the system.

Contextual Notes

Participants highlight the complexity of the reactions and the definitions of buffer systems, indicating that the discussion is limited by assumptions about the roles of strong acids and bases in buffering.

zorro
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I read somewhere that HNO3 and CH3COONa can act as a buffer solution. I know that the following solutions can act as a buffer-

1) A solution of weak acid and its salt with a strong base.
2) A solution of strong base and its salt with a strong acid.
3) A solution of a salt of weak acid and a weak base.

The above two compounds don't fit in any of these criteria.
How can they act as a buffer?
 
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Try to think about it. What compounds/ions are in solution? What are the equilibrium reactions?
 
HNO3 + CH3COONa -------> NaNO3 + CH3COOH

Here we have a mixture of salt of a strong acid and strong base and a weak acid on the product side.
So do you mean CH3COOH and CH3COONa (at equilibrium) are responsible for buffer here? What about NaNO3 and HNO3? Do they play any role? Give reason for your answer.
 
Abdul Quadeer said:
1) A solution of weak acid and its salt with a strong base.

Agreed - that will be mixture of acetic acid and sodium acetate.

2) A solution of strong base and its salt with a strong acid.

Like mixture of NaON and NaCl? It is not a classic buffer. Relatively concentrated solutions of strong bases or strong acids do resist pH changes, so in a way they are similar to buffers, but they don't require presence of salts.

3) A solution of a salt of weak acid and a weak base.

Like solution of ammonium acetate? Buffering capacity close to zero, much lower than in both earlier cases.

How can they act as a buffer?

What happens if you mix - say - 2 moles of sodium acetate, with 1 mole of nitric acid?

Edit: I see you were on the right track already. Think about composition of the solution after the reaction. Does it contain nitric acid?
 
Borek said:
What happens if you mix - say - 2 moles of sodium acetate, with 1 mole of nitric acid?

Edit: I see you were on the right track already. Think about composition of the solution after the reaction. Does it contain nitric acid?

HNO3 would be completely consumed and 1 mole of sodium acetate would remain as a reactant.
1 mole each of NaNO3 and CH3COOH are present in product side.

So here CH3COOH and CH3COONa form a buffer solution.
But we still have 1 mole of NaNO3. Will it not affect the buffer?
 
What kind of acid is nitric acid? Will this kind of acid make a buffer?
 
Abdul Quadeer said:
But we still have 1 mole of NaNO3. Will it not affect the buffer?

No, it just changes ionic strength of the solution.
 
Thanks Mr. PH
 

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