Which pair of compounds will form a buffer in aqueous solution?

Question

Which pair of compounds will form a buffer in aqueous solution?

a) HCN and NaCN b) HCl and NaOH c) NaCN and NaOH d) HCN and HCl e) HCl and NaCl f) NaCN and KCN

Answer 1 ( Expert Verified )

a) HCN and NaCN

Explanation:

Buffer solution is made by mixing either a weak base and its salt like ammonia and ammonium chloride or weak acid and its salt like HCN and its salt NaCN or acetic acid and sodium acetate .

In the given option , all of the rest of option has either strong acid or strong base or both  . In the last option both are salt so it can not form buffer solution .

It is capable of keeping the pH of the solution constant .

Answer 2 ( Expert Verified )

Buffer solutions consist of an aqueous solution of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffer solutions are used to have better control of the pH of solutions.

An example of a weak acid and its conjugate base is acetic acid (CH3COOH) and sodium acetate (CH3COONa).

Answer 3 ( Expert Verified )

Concepts and reason
The concept used to solve this problem is that a buffer is formed by the combination of a weak acid and its salt of a strong acid or by the combination of a weak base and its salt of strong acid.

Fundamentals
A buffer solution is a solution that resists change in pH on addition of a strong base or a strong acid.

Buffer solutions are of 2 types:

  1. Acidic buffer- This is formed by a weak acid and its salt of strong base.
  2. Basic buffer- This is formed by a weak base and its salt of strong acid.

Answer:

Part A
HCN and NaCN form a buffer in aqueous Solution.
Part B
HCl and NaOH don’t form a buffer in aqueous Solution.
Part C
NaOH and NaCN will not form a buffer in aqueous Solution.
Part D
HCl and HCN don’t form a buffer in aqueous Solution.
Part E
HCl and NaCl will not form a buffer in aqueous Solution.
Part F
NaCN and KCN don’t form a buffer in aqueous Solution.

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