22) D

1 – Correct

I always remember it like this: Ammonia has fewer letters (in the word Ammonia itself) than Ammonium. 

So Ammonia is NH₃ (1 less Hydrogen since it has fewer letters) and Ammonium is NH₄. 

But everyone has different ways of remembering things!

2 – Wrong

Ammonia in water is a weak alkali. So the pH would be slightly higher than 7. 

3 – Correct

Ammonia has a molecular structure.

4 – Wrong

Again, you must come up with things which help you remember concepts like these. 

I remember it like this: 

Acid has four letters and blue has four letters. So an acid turns blue litmus red. 

So Alkali must be the other way round. Alkali turns red litmus blue. 

5 – Wrong

Ammonia is a gas at room temperature. 

6. Correct

Nitrogen atom covalently bonds to 3 Hydrogen atoms to form Ammonia. 

Statements 1, 3 and 6 are correct. So D is the answer.