Question

The reaction of Zinc with dilute and concentrated nitric acid ,respectively ,produces :
A . $N{O_2}$ and $NO$
B . $NO$ and ${N_2}O$
C . $N{O_2}$ and ${N_2}O$
D . ${N_2}O$ and $N{O_2}$

Answer 1

Hint : We are aware that the reaction of nitric acid with metal depends upon the concentration of acid .There the following reaction which is asked in the problem .
Reaction of zinc with dilute nitric acid- $Zn + 10HN{O_3}(dil) \to 4Zn{(N{O_3})_2} + {N_2}O + 5{H_2}O$
Reaction of zinc with concentrated nitric acid -$Zn + 4HN{O_3}(con) \to Zn{(N{O_3})_2} + 2N{O_2} + 2{H_2}O$

Complete answer:
> We can see here when zinc metal reacts with dilute nitric acid it produces nitrous oxide which is colourless ,non-flammable gas. It is also known as laughing gas. It is mainly used for sedation and pain relief because it slows down the body’s reaction time when inhaled. It has medical uses such as anaesthetic drugs. In the second reaction concentrated nitric acid reacts with zinc metal to give nitrogen dioxide gas .Nitrogen dioxide is used as a catalyst in some oxidation reactions ,as a rocket fuel and explosive, as a flour bleaching agent. At a higher temperature it looks like reddish brown gas. It is paramagnetic in nature and has a bent shape .Mostly it is formed in the combustion process using air as oxidant while in the laboratory it is prepared by the dehydration of nitric acid.
So here the option D is correct which is ${N_2}O$ and $N{O_2}$.

Note : We have seen in this problem the reaction of nitric acid with zinc with two conditions first is when nitric acid is dilute and second one when it is concentrated .In first condition when dilute and cold nitric acid reacts with zinc it liberates Nitrous oxide $({N_2}O)$ and second condition when hot and concentrated nitric acid then it liberates reddish brown nitrogen dioxide $(N{O_2})$ gas.