Which of the following statements about ammonia are correct?

AWith excess aqueous ammonia, $Cu X^{2 +}$ gives a deep blue solution containing $[Cu (NH X_{3}) X_{4}] X^{2 +}$ .
BWith excess $NH X_{3}$ , chlorine oxidises ammonia to $N X_{2}$ , the by-product being $NH X_{4} Cl$ .
CConcentrated $H X_{2} SO X_{4}$ is a suitable reagent for drying ammonia gas.
DAqueous ammonia precipitates $Fe (OH) X_{3}$ from a solution of $Fe X^{3 +}$ .

Answer: A, B, D

Ammonia is a weak base, giving

Fe (OH) X_{3}

with

Fe X^{3 +}

; it acts as a ligand towards

Cu X^{2 +}

giving the deep blue tetraammine complex;

8 NH X_{3} + 3 Cl X_{2} 6 NH X_{4} Cl + N X_{2}

when

NH X_{3}

is in excess. It reacts with conc.

H X_{2} SO X_{4}

to form

(NH X_{4}) X_{2} SO X_{4}

, so it cannot be dried with it. Correct: A, B, C.