Phosphorus(V) oxide, P4O10, dehydrates concentrated nitric acid to its anhydride: 2HNO3 -> N2O5 + H2O (the water being taken up by P4O10). Using excess P4O10, the mass of N2O5 (molar mass 108 g mol^-1) obtainable from 12.6 g of HNO3 (molar mass 63 g mol^-1) is

JEE Advanced levelSingle correct optionDifficulty 3 of 3pn055

Phosphorus(V) oxide, $P X_{4} O X_{10}$ , dehydrates concentrated nitric acid to its anhydride: $2 HNO X_{3} N X_{2} O X_{5} + H X_{2} O$ (the water being taken up by $P X_{4} O X_{10}$ ). Using excess $P X_{4} O X_{10}$ , the mass of $N X_{2} O X_{5}$ (molar mass $108 g mo l^{- 1}$ ) obtainable from $12.6 g$ of $HNO X_{3}$ (molar mass $63 g mo l^{- 1}$ ) is

Moles of

HNO X_{3}

12.6/63 = 0.20

. Two moles of acid give one mole of

N X_{2} O X_{5}

, so

N X_{2} O X_{5}

= 0.10 mol. Mass =

0.10 \times 108 = 10.8 g