Suppose the elements P and Q combine to form two compounds PQ2 and P3Q2 . When 0.1 mole of PQ2 weight 10 g and 0.05 mole of P3Q2 weight 9 g, the atomic weights of P and Q are

Question

Suppose the elements P and Q combine to form two compounds PQ2 and P3Q2 . When 0.1 mole of PQ2 weight 10 g and 0.05 mole of P3Q2 weight 9 g, the atomic weights of P and Q are (A) 40, 30 (B) 60, 40 (C) 20, 30 (D) 30, 20

Tardigrade Admin · Accepted Answer

Let atomic weight of element P is p and that of element Q is q.

For

P Q_{2}, n = \frac{w}{M o l . wt .}

0.1 = \frac{10}{p + 2 q}

p + 2 q = \frac{10}{0.1} = 100

...(i)

For

P_{3} Q_{2}, n = \frac{w}{M o l . wt .}

0.05 = \frac{9}{3 p + 2 q}

3 p + 2 q = \frac{9}{0.05} = 180

...(ii)

On solving equation (i) and (ii) we get q = 30

p + 2 (30) = 100

p = 100 - 60 = 40

Q. Suppose the elements P and Q combine to form two compounds PQ2​ and P3​Q2​ . When 0.1 mole of PQ2​ weight 10 g and 0.05 mole of P3​Q2​ weight 9 g, the atomic weights of P and Q are

40, 30

60, 40

20, 30

30, 20

Let atomic weight of element P is p and that of element Q is q. For PQ2​,n=Mol.wt.w​ 0.1=p+2q10​ p+2q=0.110​=100 ...(i) For P3​Q2​,n=Mol.wt.w​ 0.05=3p+2q9​ 3p+2q=0.059​=180 ...(ii) On solving equation (i) and (ii) we get q = 30 p+2(30)=100 p=100−60=40

Q. Suppose the elements P and Q combine to form two compounds $P Q_{2}$ and $P_{3} Q_{2}$ . When 0.1 mole of $P Q_{2}$ weight 10 g and 0.05 mole of $P_{3} Q_{2}$ weight 9 g, the atomic weights of P and Q are