Question

0.40 g of an organic compound containing phosphorus gave 0.555 g of ${Mg}_2{P}_2{O}_7$ by usual analysis calculate the % of phosphorus in the organic compound ?

• A. 75.38 %
• B. 387.5%
• C. 38.75%
• D. 72.38%

Answer 1

The correct option is C 38.75%

Molecular mass of $M{g}_2{P}_2{O}_7=222g$

Moles of $M{g}_2{P}_2{O}_7$ in the organic compound$=\frac{0.555}{222}$

Therefore, mass of P in the organic compound$=\frac{0.555}{222}\times 31\times 2$

Therefore percentage of P in 0.4g of the organic compound$=\frac{\frac{0.555}{222}\times 62}{0.4}\times 100\%$$=38.75\%$

Hence, the correct answer is (c).