Question

P and Q are the two elements which form P2Q3 and PQ2 molecules. If 0.15 g mole of each weighs 15.9 g and 9.3g
respectively, what are the atomic masses of the elements P and Q?
​

Answer 1

Answer:

0.15 moles of P2Q3 weighs 15. 9 g

So, 1 moles of P2Q3 weigh 106 g

Now, 0.15 moles of PQ2 weigh 9.3 gm

1 mol of PQ2 will weigh 62 g

Now,

2P+3Q=106....(1)

P+4Q=62........(2)

2P+4Q=124......(3)

equation (3) - equation (1)

2P+4Q−(2P+3Q) =124−106

Q = 18, P =26

Answer 2

Explanation:

Let at. wt. of P and Q be a and b respectively

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b 

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b  and Mol. wt. of PQ2 = a + 2b 

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b  and Mol. wt. of PQ2 = a + 2b  (2a + 3b) x 0.15 = 15.9 

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b  and Mol. wt. of PQ2 = a + 2b  (2a + 3b) x 0.15 = 15.9  (a + 2b) x 0.15 = 9.3 

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b  and Mol. wt. of PQ2 = a + 2b  (2a + 3b) x 0.15 = 15.9  (a + 2b) x 0.15 = 9.3  ( wt. = Mole x Mol. wt.) 

Let at. wt. of P and Q be a and b respectively   Mol. wt. of P2Q3 = 2a + 3b  and Mol. wt. of PQ2 = a + 2b  (2a + 3b) x 0.15 = 15.9  (a + 2b) x 0.15 = 9.3  ( wt. = Mole x Mol. wt.)  a = 26, b =18