Question

Explain why an equimolar mixture of HCl (aq) and NaCl (aq) cannot be a buffer.

Answer 1

I know that a buffer solution is one which resists changes in pH when SMALL amounts of acid or base (or water) are added to it. Buffer solutions also contains comparable amounts of weak acid and its conjugate base or comparable amounts of weak base and its conjugate acid.
However, i don't know how to explain why an equimolar HCl and NaCl mixture cannot be a buffer :( Please help me !

Answer 2

your second statement answers the question: buffer solutions contain comparable amounts of WEAK acid and its conjugate

HCl\NaCl certainly is a system of an acid and its conjugate, but is HCl a WEAK acid?

Answer 3

oh xD LOL.
No because HCl is a strong acid :) ?

Answer 4

wait so... since HCl (aq) is a strong acid and NaCl is its weak conjugate base, so there will virtually be no HCl molecules to react with added OH- ions which are added to the system. Therefore the weak base cannot react with any added H+ ions? Thus it cannot be a buffer?

Answer 5

it's actually the opposite. because HCl is such a strong acid, the \(backwards\) reaction of the conjugate base will not absorb \(H^+\) ions. The strong acid will push the entire system forward, so it is not a buffer

Answer 6

oh oops!
Thank you so much :))

Answer 7

when you say it would push the entire system forward. Do you mean the equilibrium would shift to the right? Or am i going off topic?

Answer 8

it would shift the equilibrium to the right. because the HCl is SUCH a strong acid, the reaction is said to not be at equilibrium anymore, but we can treat it as if it does

Answer 9

oh okay ^_^ Just making sure