Step 1: Understanding the Question:
The problem requires balancing a redox reaction to find the stoichiometric coefficient $x$ accompanying the hydrogen peroxide ($\text{H}_2\text{O}_2$) and oxygen gas ($\text{O}_2$).
Step 2: Detailed Explanation:
Let us balance the equation using the half-reaction method in an acidic/neutral framework:
1.
Oxidation Half-Reaction ($\text{H}_2\text{O}_2 \rightarrow \text{O}_2$):
Oxygen changes its oxidation state from $-1$ in peroxide to $0$ in molecular oxygen.
Balancing atoms and charges:
$$ \text{H}_2\text{O}_2 \rightarrow \text{O}_2 + 2\text{H}^+ + 2\text{e}^- \quad \text{--- (Equation 1)} $$
2.
Reduction Half-Reaction ($\text{ClO}_4^- \rightarrow \text{ClO}_2^-$):
Chlorine drops from an oxidation state of $+7$ to $+3$ (a gain of $4\text{e}^-$).
Balancing oxygens with water and hydrogens with $\text{H}^+$:
$$ \text{ClO}_4^- + 4\text{H}^+ + 4\text{e}^- \rightarrow \text{ClO}_2^- + 2\text{H}_2\text{O} \quad \text{--- (Equation 2)} $$
3.
Equalizing Electron Flow:
Multiply Equation 1 by 2 so that it releases $4\text{e}^-$, balancing Equation 2:
$$ 2\text{H}_2\text{O}_2 \rightarrow 2\text{O}_2 + 4\text{H}^+ + 4\text{e}^- $$
4.
Combining the Half-Reactions:
Adding the balanced expressions together cancels out the $4\text{e}^-$ and $4\text{H}^+$ ions perfectly:
$$ 2\text{H}_2\text{O}_2 + \text{ClO}_4^- \rightarrow 2\text{O}_2 + \text{ClO}_2^- + 2\text{H}_2\text{O} $$
Comparing this balanced result to the question's format yields $x = 2$.
Step 3: Final Answer:
The correct coefficient value is 2, matching option (D).