The value of oxidation number of chlorine in $ HClO_3 $ is: · Electrochemistry MDCAT Past Paper MCQ

Chemistry Electrochemistry SET 2019

PMDC Verified Question 47 of 73

The value of oxidation number of chlorine in $ HClO_3 $ is:

-1

Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:

Option B: +5

Concept:

For a neutral molecule, the sum of the oxidation states of all the constituent atoms must equal exactly zero.

Formula:

$$(+1) + x + 3(-2) = 0$$

Solution:

Hydrogen (H) generally has an oxidation state of $ +1 $.

Oxygen (O) is $ -2 $.

Let $ x $ be the oxidation state of Chlorine (Cl).

Set up the equation: $ 1 + x - 6 = 0 $.

Solve for $ x $: $ x - 5 = 0 \implies x = +5 $.

Why other options are incorrect:

Chlorine shows $ -1 $ in hydrochloric acid ($ HCl $), $ +3 $ in chlorous acid ($ HClO_2 $), and $ +7 $ in perchloric acid ($ HClO_4 $).

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