Which of the following statements about the action of heat on nitrates are correct?

A $NaNO X_{3}$ gives $NaNO X_{2}$ and $O X_{2}$ only.
B $Cu (NO X_{3}) X_{2}$ gives black CuO, brown $NO X_{2}$ and $O X_{2}$ .
C $NH X_{4} NO X_{3}$ on careful heating gives $N X_{2} O$ and water.
D $KNO X_{3}$ on moderate heating gives brown fumes and a residue of $K X_{2} O$ .

Answer: A, B, C

Nitrates of Na and K (alkali metals) give nitrite and oxygen, so statement 1 is true and statement 4 is false. Copper nitrate gives the oxide,

NO X_{2}

and

O X_{2}

. Ammonium nitrate gives

N X_{2} O

and

H X_{2} O

on careful heating. Statements 1, 2 and 3 are correct.