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MolSynapse / Question bank / p-Block Elements: Groups 15 and 16 / Phosphorus allotropes, phosphine, halides and oxyacids of phosphorus

JEE Advanced levelSingle correct optionDifficulty 3 of 3pn054

White phosphorus ( $12.4 g$ , $P X_{4}$ ; P = 31) is boiled with excess concentrated $NaOH$ solution in an inert atmosphere: $P X_{4} + 3 NaOH + 3 H X_{2} O PH X_{3} + 3 NaH X_{2} PO X_{2}$ . The mass of sodium hypophosphite, $NaH X_{2} PO X_{2}$ (molar mass $88 g mo l^{- 1}$ ), formed is

A $8.8 g$
B $17.6 g$
C $35.2 g$
D $26.4 g$

Answer: D

Molar mass of

P X_{4}

= 124, so moles =

12.4/124 = 0.10

. One mole of

P X_{4}

gives 3 mol

NaH X_{2} PO X_{2}

, i.e. 0.30 mol. Mass =

0.30 \times 88 = 26.4 g

.

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