In: Chemistry

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

Which pair of compounds will form a buffer in aqueous solution?
• NaCN and NaOH
• NaCN and KCN
• HCl and NaOH
• HCN and HCl
• HCN and NaCN
• HCl and NaCl

## Solutions

##### Expert Solution

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 a strong acid.

Fundamentals

A buffer solution is a solution that resists change in $$\mathrm{pH}$$ on the addition of a strong base or a strong acid. Buffer solutions are of 2 types:

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

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

To form a buffer solution you must mix a weak acid and a weak base on an aqueous solution.
The last option: HCN and NaCN will form a buffer.

Once you put HCN and NaCN in water will occur the following molecular dissociation:
HCN -----> H+ + CN-
NaCN -----> Na+ + CN-

The HCN will act as a weak acid and NaCN as a conjugated base.