Question

When the ammonia reacts with oxygen gas at high temperature following reactions are observed. Based on the given reactions and observations, identify R and S.​
4 ${NH}_3$ + 5 $O_2$ → 6 $H_{2}O$ + R + Heat​

R + $O_2$ → S (brown gas)​

Reddish brown fumes are observed in the flask during oxidation.​

• A. R: ${NO}_2$; S:$NO$;
• B. R: $NO$; S:$N_2{O}_5$
• C. R: ${NO}_2$; S: $N_2{O}_5$
• D. R: $NO$; S: ${NO}_2$

Answer 1

The correct option is D

R: $NO$; S: ${NO}_2$

Ammonia gas is oxidised by oxygen in the presence of platinum at 800${}^o$C. The products of this reaction are water and nitrogen oxide gas. The nitrogen oxide gas will get oxidised to give nitrogen dioxide. Brown vapours evolve when ammonia and oxygen gas are passed over platinum heated at 800${}^o$C in a combustion tube.
Chemical reaction is given as:
4 ${NH}_3$ (g) + 5 $O_2$ (g) → 6 $H_{2}O$ (g) + 4 $NO$ (g) + Heat​
NO(g) + $O_2$(g) → 2 ${NO}_2$ (brown gas)​

The correct answer is option (b).