White phosphorus disproportionates in alkaline solution: P4 + OH^- + H2O -> PH3 + H2PO2^-. Balance the equation and calculate the mass of PH3 formed from 12.4 g of P4. Atomic masses: P 31, H 1 (so P4 = 124 g/mol and PH3 = 34 g/mol). Give the answer in grams to two decimal places.

JEE Advanced levelNumerical answerDifficulty 3 of 3rx081

White phosphorus disproportionates in alkaline solution: $P X_{4} + OH X^{-} + H X_{2} O PH X_{3} + H X_{2} PO X_{2} X^{-}$ . Balance the equation and calculate the mass of $PH X_{3}$ formed from 12.4 g of $P X_{4}$ . Atomic masses: P 31, H 1 (so $P X_{4}$ = 124 g/mol and $PH X_{3}$ = 34 g/mol). Give the answer in grams to two decimal places.

Numerical answer type, answer in g, tolerance 0.02.

Balanced:

P X_{4} + 3 OH X^{-} + 3 H X_{2} O PH X_{3} + 3 H X_{2} PO X_{2} X^{-}

(3 P go 0 to +1, 1 P goes 0 to -3). n(

P X_{4}

) = 12.4/124 = 0.10 mol and 1 mol

P X_{4}

gives 1 mol

PH X_{3}

. Mass = 0.10 x 34 = 3.40 g.