pBlock ElementsII - Result Question 126

####11. The pair in which phosphorus atoms have a formal oxidation state of +3 is

(2016 Main)

(a) pyrophosphorous and hypophosphoric acids

(b) orthophosphorous and hypophosphoric acids

(c) pyrophosphorous and pyrophosphoric acids

(d) orthophosphorous and pyrophosphorous acids

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Solution:

  1. Orthophosphorous acid, $H _3 PO _3: HO-{ } _P^{P}-OH$

$H _3 PO _3=3+x+3(-2)=0$ or $x=+3$

Pyrophosphorous acid, $H _4 P _2 O _5$ :

$H _4 \stackrel{x}{P} O _5=4+2 x+5(-2)=0$

$4+2 x-10=0, x=+3$



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