Answer
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