In which of the following reactions, $\mathrm{H}_{2} \mathrm{SO}_{4}$ acts as an oxidising agent?

In which of the following reactions, $\mathrm{H}_{2} \mathrm{SO}_{4}$ acts as an oxidising agent?
  1. $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{conc}) \longrightarrow 6 \mathrm{C}+6 \mathrm{H}_{2} \mathrm{O}$
  2. $5 \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{conc})+4 \mathrm{Zn} \longrightarrow \mathrm{H}_{2} \mathrm{S}+4 \mathrm{Zn}^{2+}+4 \mathrm{SO}_{4}{ }^{2-}+4 \mathrm{H}_{2} \mathrm{O}$
  3. $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{dil})+\mathrm{Zn} \longrightarrow \mathrm{Zn}^{2+}+\mathrm{H}_{2}+\mathrm{SO}_{4}^{2-}$
  4. Both Option 2 and 3 are correct

Solution

a. As a dehydrating agent, since it simply removes water from glucose.
b. $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{~S}$ in $+6$ state $) \longrightarrow \mathrm{H}_{2} \mathrm{S}$ ($\mathrm{S}$ in $-2$ state), i.e., acid is reduced. So it acts as an oxidising agent.
c. All strong acids liberate $\mathrm{H}_{2}$ with active metals such as $\mathrm{Zn}$ (i.e., it is reduced) unless $\mathrm{SO}_{4}{ }^{2-}$ is reduced. In this case, $\mathrm{H}^{\oplus}$ is reduced to $\mathrm{H}_{2}$. So it acts as an oxidising agent. We can also call it as an acidic property. ~

Asked in: JEE-TOPICTESTS-CHEMISTRY

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