Question

In which of the following reactions, the underlined substance has been reduced?

• A. $\underline{CO} + CuO\rightarrow \underline{CO_2} + Cu$
• B. $\underline{CuO} + 2 HCl\rightarrow \underline{CuCl_2} + H_2O$
• C. $\underline{4H_2O} (g) + 3 Fe \rightarrow \underline{4H_2} (g) + Fe_3O_4$
• D. $\underline{C} + 4 HNO_3 \rightarrow \underline{CO_2} + 2H_2O + 4 NO_2$

Answer 1

Answer: (C)

a) $\overset{+2}{C} O \longrightarrow \overset{+4}{C}O _2$
b) $\overset{+2}{C}uO \longrightarrow \overset{+2}{C} uCl _2$
c) $\overset{+1}{H} _2 O \longrightarrow \overset{0}{ H _2}$
d) $\overset{0}{ C } \longrightarrow \overset{+4}{C} O _2$
Only in (c), O.N. of hydrogen decreases from +1 to 0 and hence $H _2 O$ gets reduced to $H _2$