Phosphorous acid disproportionates on heating: 4H3PO3 -> 3H3PO4 + PH3. Complete decomposition of 8.20 g of H3PO3 (molar mass 82 g mol^-1) gives how much phosphoric acid (molar mass 98 g mol^-1)?

JEE Advanced levelSingle correct optionDifficulty 3 of 3pn049

Phosphorous acid disproportionates on heating: $4 H X_{3} PO X_{3} 3 H X_{3} PO X_{4} + PH X_{3}$ . Complete decomposition of $8.20 g$ of $H X_{3} PO X_{3}$ (molar mass $82 g mo l^{- 1}$ ) gives how much phosphoric acid (molar mass $98 g mo l^{- 1}$ )?

Moles of

H X_{3} PO X_{3}

8.20/82 = 0.100

. Four moles give three moles of

H X_{3} PO X_{4}

, so

H X_{3} PO X_{4}

0.100 \times 3/4 = 0.075

mol. Mass =

0.075 \times 98 = 7.35 g

(the remaining 0.85 g is

PH X_{3}