two chem mc

1.
The answer is b.

In ammonia solution, the dissolved ammonia reacts with water (reversible reaction) to give ammonium and hydroxide ions.
NH3(aq) + H2O(l) = NH4+(aq) + OH- (aq)
The solution becomes alkaline because of the presence of OH- (aq) ions (, but not NH4+ ions).

2.
The answer is c .

a. incorrect
Copper reacts with dilute nitric acid to give copper(II) ions, which then react with sodium hydroxide solution to give a blue precipitate of copper(II) hydroxide. The precipitate is NOT white in colour.

b. incorrect
Iron reacts with dilute nitric acid to give iron(III) ions, which then react with sodium hydroxide solution to give a brown precipitate of iron(III) hydroxide. The precipitate is NOT white in colour.

c. correct
Lead reacts with dilute nitric acid to give lead(II) ions, which then react with sodium hydroxide solution to give a white precipitate of lead(II) hydroxide. The precipitate dissolves in excess sodium hydroxide solution.

d. incorrect
Magnesium reacts with dilute nitric acid to give magnesium ions, which then reacts with sodium hydroxide solution to give a white precipitate of magnesium hydroxide. The precipitate does NOT dissolve in excess sodium hydroxide solution.
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