Question

Cl₂O₇ is the anhydride of which acid?

• A. Hypochlorous acid (HClO)
• B. Chlorous acid (HClO₂)
• C. Chloric acid (HClO₃)
• D. Perchloric acid (HClO₄)

Hint:

Higher oxides of chlorine (like Cl\textsubscript{2}O\textsubscript{7}) form oxyacids with higher oxidation states. Cl\textsubscript{2}O\textsubscript{7} corresponds to perchloric acid, where Cl is in +7 state.

Answer 1

The Correct Option is D

Step 1: Understand what an acid anhydride is
An acid anhydride is an oxide that, when reacted with water, forms an oxyacid. For non-metals like chlorine, this is especially common. Step 2: Identify the oxide and write its hydrolysis reaction
The molecular formula given is Cl₂O₇, which is the heptoxide of chlorine. When it reacts with water: \[ \text{Cl}_2\text{O}_7 + \text{H}_2\text{O} \rightarrow 2 \text{HClO}_4 \] This reaction yields perchloric acid (HClO₄), a strong acid where chlorine is in the +7 oxidation state. 
Step 3: Conclusion
Cl₂O₇ is the anhydride of perchloric acid (HClO₄). \[ \boxed{\text{Cl}_2\text{O}_7 \rightarrow \text{Anhydride of } \text{HClO}_4} \]