Question

Why an aqueous solution of NH4Cl is acidic while that of HCOOK is basic

Answer 1

Answer:

Explanation:

When NH4Cl dissolved in water it hydrolyses to weak base NH4OH and strong acid HCl. So, the aqueous solution of NH4Cl is acidic due to presence of excess H3O+ ion concentration over OH- ion. It can be explained with the help of Bronsted Lowery concept of acid-base. NH4+ ion is the conjugate acid of weak base NH3. So, it is strong conjugate acid and strongly reacts with water and forms huge number of H3O+ ions. But, as Cl- is conjugate base of strong acid HCl, it is weak base and it almost doesn't react with water to produce H3O+ ion.

NH4+(aq) + 2 H2O(l) → NH4OH (aq) + H3O+ (aq)

When HCOOK is dissolved in water, it hydrolyses to weak acid, formic acid, HCOOH and strong base, potassium hydroxide, KOH. So, the aqueous solution of HCOOK is alkaline due to presence of excess OH- concentration over H3O+. Again, HCOO- is conjugate base of weak acid HCOOH, so it is strong base and reacts with water to form huge number of OH- ions. So, the solution is alkaline.

HCOO-(aq) + H2O(l) → HCOOH (aq) + OH- (aq)

Hope this helps.

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Answer 2

An aqueous solution of NH4Cl is acidic while that of HCOOK is basic because they hydrolyzed to form a strong acid and strong base respectively.

• In nature, NH4Cl is an acidic salt created by neutralising a strong acid, HCl with a weak base, NH4OH. As a result of the excess H+ concentration over OH- the solution is mildly acidic.
• When HCOOK is dissolved in water, it hydrolyzes into HCOOH and KOH. HCOOH is a weak acid while KOH is a strong base. As a result of the excess OH- concentration over H3O+, the aqueous solution of HCOOK is alkaline.