The order of the oxidation state of the phosphorus atom in $\mathrm{H}_{3} \mathrm{PO}_{2}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{H}_{3} \mathrm{PO}_{3}$, and $\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}$ is

(C) $\mathrm{H}_{3} \mathrm{PO}_{4}>\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}>\mathrm{H}_{3} \mathrm{PO}_{3}>\mathrm{H}_{3} \mathrm{PO}_{2}$

(A) $\mathrm{H}_{3} \mathrm{PO}_{3}>\mathrm{H}_{3} \mathrm{PO}_{2}>\mathrm{H}_{3} \mathrm{PO}_{4}>\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}$

(B) $\mathrm{H}_{3} \mathrm{PO}_{4}>\mathrm{H}_{3} \mathrm{PO}_{2}>\mathrm{H}_{3} \mathrm{PO}_{3}>\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}$

(D) $\mathrm{H}_{3} \mathrm{PO}_{2}>\mathrm{H}_{3} \mathrm{PO}_{3}>\mathrm{H}_{4} \mathrm{P}_{2} \mathrm{O}_{6}>\mathrm{H}_{3} \mathrm{PO}_{4}$

JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Redox Reactions and Electrochemistry

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The order of the oxidation state of the phosphorus atom in

H_{3} PO_{2}, H_{3} PO_{4}, H_{3} PO_{3}

, and

H_{4} P_{2} O_{6}

(A) $H_{3} PO_{3} > H_{3} PO_{2} > H_{3} PO_{4} > H_{4} P_{2} O_{6}$
(B) $H_{3} PO_{4} > H_{3} PO_{2} > H_{3} PO_{3} > H_{4} P_{2} O_{6}$
(C) $H_{3} PO_{4} > H_{4} P_{2} O_{6} > H_{3} PO_{3} > H_{3} PO_{2}$ ✓ Correct
(D) $H_{3} PO_{2} > H_{3} PO_{3} > H_{4} P_{2} O_{6} > H_{3} PO_{4}$

Answer: (C)

Solution

The oxidation states of phosphorus in the given compounds are:

Species	Oxidation state of P
$H_{3} PO_{4}$	+5
$H_{4} P_{2} O_{6}$	+4
$H_{3} PO_{3}$	+3
$H_{3} PO_{2}$	+1

Therefore, the order is:

H_{3} PO_{4} > H_{4} P_{2} O_{6} > H_{3} PO_{3} > H_{3} PO_{2}

JEE Advanced · 2017 · 21 May 2017 · Paper 2 · Single correct option

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