Question

Which of the following is not an intermolecular redox reaction?

• A. $MgCO _3 \rightarrow MgO + CO _2$
• B. $O _2+2 H _2 \rightarrow 2 H _2 O$
• C. $K + H _2 O \longrightarrow KOH +(1 / 2) H _2$
• D. $MnBr _3 \rightarrow MnBr _2+(1 / 2) Br _2$

Answer 1

Answer: (A)

Intermolecular redox reaction and redox reactions are same.
a. Oxidation states of $Ca$ and $C$ are $+2$ and $+4$, respectively, in both reactant and product: hence, not redox,
b. $4 e ^{-}+ O _2 \rightarrow 2 O ^{2-}$ (Reduction)
$H _2 \rightarrow 2 H ^{\oplus}+2 e ^{-}$(Oxidation)Hence, redox
c. $Na \rightarrow Na ^{\oplus}+ e ^{-}$(Oxidation)
$2 H ^{\oplus}+2 e ^{-} \rightarrow H _2$ (Reduction) Hence, redox
d. $e ^{-}+ Mn ^{3+} \rightarrow Mn ^{2+}$ (Reduction)
$2 Cl ^{\ominus} \rightarrow Cl _2+2 e ^{-}$(Oxidation) Hence, redox