Question

Referring to the following reactions the missing products A,B,C, and D respectively are

• A. $N_2,N_2,NO,N{O}_2$
• B. $N_2,N{H}_3,N_2,NO$
• C. $N_2,N_2,N{O}_2,N{O}_2$
• D. $N_2,N{H}_3,N{O}_2,N_2{O}_4$

Answer 1

Answer: (A)

(i) In the laboratory, dinitrogen is prepared by treating an aqueous solution of ammonium chloride with sodium nitrite.
$N{H}_{4}Cl(aq)+NaN{O}_2(aq)\to N_2(g)+2H_{2}O(l)+NaCl(aq)$
Small amounts of $NO$ and $HN{O}_3$ are also formed as impurities, which can be removed by passing the gas through aqueous sulphuric acid containing potassium dichromate.
(ii) Dinitrogen can also be prepared by heating ammonium dichromate
${\left(N{H}_4\right)}_{2}C{r}_2{O}_7(s)\stackrel{\Delta }{⟶}{N}_2(g)+4H_{2}O(l)+C{r}_2{O}_3(s)$
(iii) Copper metal reacts with dilute $HN{O}_3$ to form nitrogen (II) oxide (NO)
$3Cu(s)+8HN{O}_3(\text{ dilute })\to 3Cu{\left(N{O}_3\right)}_2(aq)+2NO(g)+4H_{2}O(l)$
(iv) Copper metal reacts with conc. $HN{O}_3$ to form nitrogen (IV) oxide or nitrogen dioxide $\left(N{O}_2\right)$.
$Cu(s)+4HN{O}_3\text{ (conc. })\to Cu{\left(N{O}_3\right)}_2(aq)+2N{O}_2(g)+2H_{2}O(l)$$N{H}_{4}Cl(aq)+NaN{O}_2(aq)\to N_2(g)+2H_{2}O(l)+NaCl(aq)$
Small amounts of $NO$ and $HN{O}_3$ are also formed as impurities, which can be removed by passing the gas through aqueous sulphuric acid containing potassium dichromate.
(ii) Dinitrogen can also be prepared by heating ammonium dichromate
${\left(N{H}_4\right)}_{2}C{r}_2{O}_7(s)\stackrel{\Delta }{⟶}{N}_2(g)+4H_{2}O(l)+C{r}_2{O}_3(s)$
(iii) Copper metal reacts with dilute $HN{O}_3$ to form nitrogen (II) oxide (NO)
$3Cu(s)+8HN{O}_3(\text{ dilute })\to 3Cu{\left(N{O}_3\right)}_2(aq)+2NO(g)+4H_{2}O(l)$
(iv) Copper metal reacts with conc. $HN{O}_3$ to form nitrogen (IV) oxide or nitrogen dioxide $\left(N{O}_2\right)$.
$Cu(s)+4HN{O}_3\text{ (conc. })\to Cu{\left(N{O}_3\right)}_2(aq)+2N{O}_2(g)+2H_{2}O(l)$