Question

The mass of phosphoric acid required to obtain $53.4$ g pyrophosphoric acid is :

• A. 58.8 g
• B. 60.2 g
• C. 65.8 g
• D. 68.3 g

Answer 1

The correct option is A 58.8 g

$2H_{3}P{O}_4\to H_4{P}_2{O}_7+H_{2}O$

One mole of pyrophosphoric acid will require two moles of phosphoric acid.

The molar masses of pyrophosphoric acid and phosphoric acid are $177.98$ g/mol and $98$ g/mol respectively.

$177.98$ gm of pyrophosphoric acid requires $2\times 98$ gm phosphoric acid.

Therefore 53.4 gm requires $\frac{2\times 98\times 53.4}{177.98}$ gm of phosphoric acid.

$=58.8gm$

Hence, option A is correct.