Bleaching powder and bleach solution are produced on a large scale and used in several household products. The effectiveness of bleach solution is often measured by iodometry. Bleaching powder contains a salt of an oxoacid as one of its components. The anhydride of that oxoacid is

P Block Elements PYQ — JEE Advanced 2012 · Shift 2 · Q13 with Solution

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Correct answer: A

Identify the oxoacid-related salt present in bleaching powder

Bleaching powder is commonly represented as calcium oxychloride, and it contains the hypochlorite component.

The relevant oxoacid is therefore hypochlorous acid: $HClO$
Find the acid anhydride of hypochlorous acid

The anhydride is the oxide which forms the acid on reaction with water.

Check: $Cl_2O + H_2O \rightarrow 2HClO$

Thus, $Cl_2O$ is the anhydride of hypochlorous acid.
Evaluate the options
- A: $Cl_2O$ gives $HClO$ on hydration, so this is correct.
- B: $Cl_2O_7$ is the anhydride of perchloric acid, $HClO_4$ .
- C: $ClO_2$ is chlorine dioxide, not the anhydride of $HClO$ .
- D: $Cl_2O_6$ is related to chloric/perchloric oxidation states, not $HClO$ .
Final answer

The required anhydride is: $\boxed{Cl_2O}$

So, the correct option is A.