Question

When dissolved in aqueous solution, which pair would behave as a buffer?

A) HCl and NaCl
B) KOH and KCl
C) HNO2 and NaNO2
D) HNO3 and NH4NO3
E) Ca(OH)2 and CaSO4

Answer 1

You can make buffers in the following ways:
a weak acid and a salt of its conjugate base in solution
or
a weak acid and enough strong base to neutralize a portion of the weak acid
or
a weak base and enough strong acid to neutralize a portion of the weak base

Answer 2

Thanks for the reply, so:

A) HCl and NaCl
A weak acid (HCl) and its conjugate base in solution (Cl- from NaCl)

B) No acid present

C) HNO2 and NaNO2
A weak acid (HNO2) and its conjugate base in solution (NO2- from NaNO2)

D) HNO3 and NH4NO3
A strong acid (HNO3) and a weak base NH4NO3

E) No acid present.

So it's either A, C, or D.

I know it can't be two of them but how can I eliminate them? I've got to be wrong on two ;P

Answer 3

HCl is not a weak acid

Answer 4

oops xD

so A) HCl (Strong acid) and NaCl (Weak base)

Cl- is the conjugate base.

How do I know if it's A, C, or D?

Answer 5

it's not A, NaCl is not an acid nor a base

I would go with C because it's a weak acid and it's conjugate base

Answer 6

C can be a buffer, i'm not completely sure about D

Answer 7

okay. So in that case answer D bothers you because the NH4NO3 can be rewritten as H4N2O3, an conjugates are defined as add/remove H+ proton? :D

Answer 8

yeah NH4NO3 is a weak acid

Answer 9

Alright cool :)

Answer 10

(Y)