Which of the following is an endothermic process
(i) $O (g) + e^{-} \to O^{-} (g)$
(ii) $N (g) + e^{-} \to N^{-} (g)$
(iii) $Cl^{-} (g) ⟶ Cl (g) + e^{-}$
(iv) $O^{-} (g) + e^{-} \to O^{- 2} (g)$

Question

Which of the following is an endothermic process

(i) $O (g) + e^{-} \to O^{-} (g)$

(ii) $N (g) + e^{-} \to N^{-} (g)$

(iii) $Cl^{-} (g) ⟶ Cl (g) + e^{-}$

(iv) $O^{-} (g) + e^{-} \to O^{- 2} (g)$

TestHub · Accepted Answer

An endothermic process is one in which energy is absorbed during the reaction.

(i) $O (g) + e^{-} \to O^{-} (g)$ is generally exothermic (first electron affinity).

(ii) $N (g) + e^{-} \to N^{-} (g)$ is endothermic due to the stable half-filled 2p³ configuration of nitrogen.

(iii) $C l^{-} (g) \to Cl (g) + e^{-}$ requires energy, so it is endothermic.

(iv) Adding a second electron to oxygen, $O^{-} (g) + e^{-} \to O^{2 -} (g)$ , is also endothermic due to repulsion.

Hence, the correct options are II, III and IV.

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