Question

A substance, A2B, has the composition by mass of 60% A and 40% B. What is the composition of AB2 by mass?a)40% A, 60% Bb)50% A, 50% Bc)27% A, 73% Bd)33% A, 67% Be)none of these

Answer 1

The composition by mass of AB2 is 27% A, and 73% B

Explanation:

Assuming a basis of 100g

A substance A2B has the composition by mass of 60% A and 40% B

Since we assumed a basis of 100g

A is 60g by mass

B is 40g by mass

Since, there are two As

2A = 60 grams

A = 60/2

A = 30 grams

Each A is 30 grams

B = 40 grams

AB2, would have a total mass of

1 x mass of A + 2 x mass of B

30 + 2*40

30 + 80 = 110grams

The new composition by mass of AB2 can be calculated as follows

A = 30 /110 * 100%

A = 0.2727 x 100%

A = 27.27%

B = 80/110 * 100%

B = 0.7272 x 100%

B = 72.72 %

Hence, the composition by mass of AB2 is 27%A, and 73% B