Q108 / 270 · NDA 2025 (Phase 2) · General Ability
Which one of the following is an endothermic reaction?
- A$CH_4(g) + 2O_2(g) \rightarrow CO_2(g) + 2O_2(g)$
- B$C_6H_{12}O_6(aq) + 6O_2(g) \rightarrow 6CO_2(g) + 6H_2O(l)$
- C$N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$
- Correct answerD$2Pb(NO_3)_2(s) \rightarrow 2PbO(s) + 4NO_2(g) + O_2(g)$
Solution
Combustion of methane ($CH_4$) is an exothermic reaction as it releases heat.
The oxidation of glucose ($C_6H_{12}O_6$) during respiration is an exothermic process that provides energy to living cells.
The synthesis of ammonia ($NH_3$) from nitrogen and hydrogen (Haber process) is an exothermic reaction.
The thermal decomposition of lead nitrate ($Pb(NO_3)_2$) requires heat to break down the reactant into simpler products ($PbO$, $NO_2$, and $O_2$). Since heat is absorbed, it is an endothermic reaction.
Answer: $2Pb(NO_3)_2(s) \rightarrow 2PbO(s) + 4NO_2(g) + O_2(g)$
The oxidation of glucose ($C_6H_{12}O_6$) during respiration is an exothermic process that provides energy to living cells.
The synthesis of ammonia ($NH_3$) from nitrogen and hydrogen (Haber process) is an exothermic reaction.
The thermal decomposition of lead nitrate ($Pb(NO_3)_2$) requires heat to break down the reactant into simpler products ($PbO$, $NO_2$, and $O_2$). Since heat is absorbed, it is an endothermic reaction.
Answer: $2Pb(NO_3)_2(s) \rightarrow 2PbO(s) + 4NO_2(g) + O_2(g)$
Hence, the correct answer is option: 'D'.