Question

A buffer solution can be prepared from a mixture of- [jee 1999] (a) sodium acetate and acetic acid in water (b) sodium acetate and hydrochloric acid in water (c) ammonia and ammonium chloride in water (d) ammonia and sodium hydroxide in water.

Answer 1

A buffer is a solution containing either a weak acid and its salt or a weak base and its salt, which is resistant to changes in pH.

So your answers are a and c.

Answer 2

Answer: (a) sodium acetate and acetic acid in water

Explanation:

Buffer is a solution which resists changes in pH when small quantities of acid or alkali are added to it.

It is formed by combination of weak acid and salt of weak acid with strong base called as acidic buffer.Example: $CH_3COOH$ and $CH_3COONa$

Or it is formed by combination of weak base and salt of weak base with strong acid called as basic buffer buffer. Example: $NH_4OH$ and $NH_4Cl$

When acid is added to buffer, the buffer releases $OH^-$ ions to neutralize the acid added and when base is added to buffer, the buffer releases $H^+$ ions to neutralize the base added.