It is found that in 11.2 litres of any gaseous compound of phosphorus at NTP, there is never less than 15.5 g of P. Also, this volume of the vapour of phosphorus itself at NTP weighs 62 g. What should be the atomic weight and molecular weight of phosphorus?

Explanation

Since 1 mole of any phosphorus compound contains at least 1 mole of P atoms, and also `22.4` litres (at NTP) of the gaseous compound contains 31 g of phosphorus, therefore, 1 mole of phosphorus weighs 31 g, i.e., 31 is the atomic weight of phosphorus. Similarly, the molecular weight of phosphorus is 124 as 1 mole of its vapour weighs 124 g.