Two elements P and Q form P2O3 and PQ2. If 0.15 mole of P2Q3 weigh 15.9g and 0.5 mole of PQ2 weigh 9.3 g. Find atomic mass of P and Q.

Lets assume the atomic masses of P and Q are x and y respectively.

 

Mw of P2Q3 = 2 x + 3 y 

MW of PQ2 = x + 2 y

 

we know moles = weight/ mw

 

so, 2x + 3y = 15.9/ 0.15 

x + 2y = 9.3/ 0.15

 

Solving these equations, you will get x= 26, y =18