The reaction of HClO_3 with HCl gives a paramagnetic gas, which upon reaction with O_3 produces

P Block Elements PYQ — JEE Advanced 2022 · Shift 2 · Q16 with Solution

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Correct answer: C

Chloric acid oxidizes hydrochloric acid. The reaction is:

\mathrm{HClO_3 + 3HCl \rightarrow ClO_2 + \tfrac{1}{2}Cl_2 + 2H_2O}

A better balanced integer form is:

2\mathrm{HClO_3} + 2\mathrm{HCl} \rightarrow 2\mathrm{ClO_2} + \mathrm{Cl_2} + 2\mathrm{H_2O}

The important product here is $\mathrm{ClO_2}$ .

$\mathrm{ClO_2}$ has an odd number of electrons, so it contains one unpaired electron. Hence, it is paramagnetic.

Therefore, the paramagnetic gas mentioned is:

\mathrm{ClO_2}

Ozone oxidizes chlorine dioxide to chlorine trioxide radical:

\mathrm{ClO_2 + O_3 \rightarrow ClO_3 + O_2}

Then two $\mathrm{ClO_3}$ units dimerize to form:

2\mathrm{ClO_3} \rightarrow \mathrm{Cl_2O_6}

So overall, the product formed is:

\mathrm{Cl_2O_6}

A: $\mathrm{Cl_2O}$ — incorrect
B: $\mathrm{ClO_2}$ — this is the intermediate gas, not the final product with $\mathrm{O_3}$
C: $\mathrm{Cl_2O_6}$ — correct
D: $\mathrm{Cl_2O_7}$ — incorrect

The paramagnetic gas is $\mathrm{ClO_2}$ , and on reaction with $\mathrm{O_3}$ it gives:

\boxed{\mathrm{Cl_2O_6}}