How many of the following statement(s) is/are correct for making a buffer solution ?
(i) It can be formed by mixing equal concentrations of HCl and CH 3 COONa
(ii) It can be formed by mixing equal concentrations of HNO 3 and NH 3
(iii) It can be formed by mixing equal concentrations of HCOOH and Aniline.
(iv) It can be formed by mixing equal volumes of NH 4 OH and HClO 4 .
(v) It can be formed by mixing equal volumes of HCN and KOH.
(vi) There is no change in the pH of a buffer solution on adding small amount of a strong acid/base.
(vii) The concentrations of acid and base being mixed must be different to form a buffer.
(viii) The volumes of acid and base being mixed must be different to form a buffer.
(ix) The concentrations and volumes of acid and base being mixed must be different to form a buffer.
Text Solution
Verified by Experts(i) (equal concentrations); (ii) (equal concentrations); (iv) (equal volumes); (v) (equal volumes)
[5 (i) to (v)]
For a buffer solution, we need:
A weak acid + its salt with a strong base, or
A weak base + its salt with a strong acid.
Let's check each statement:
(i) 
(equal concentrations)
Partial reaction leaves 
and 
buffer.
(ii) 
(equal concentrations)
Forms 
; with equimolar amounts 
is completely neutralized → not a buffer.
(iii) 
Aniline (equal concentrations)
Weak acid + weak base produce salt; not a standard buffer.
(iv) 
(equal volumes)
Weak base + strong acid in equivalent amounts gives only salt → not a buffer.
(v) 
(equal volumes)
Partial neutralization gives 
buffer.
(vi) No change in pH on adding small amount of strong acid/base pH changes slightly; it is not exactly unchanged.
(vii) Concentrations of acid and base being mixed must be different
(viii) Volumes being mixed must be different
(ix) Both concentrations and volumes must be different
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