Elements A and B form two new compounds. In compound I, 2 grams of A is combined with 4 grams of B. In compound II, 4 grams of A is combined with 12 grams of B. If the formula of compound I is A2B, what is the formula of compound II?

They tell you that compound A2B has twice the mass of B as A. That requires that element A have 1/4 the mass of B.

For a compound to have three times more B than A (my mass), the formula must be A4B3, or (A4B3)n, where n is an integer

To find the formula of compound II, we need to compare the ratios of the masses of elements A and B in both compounds.

In compound I, we have 2 grams of A combined with 4 grams of B. So the ratio of the mass of A to B is 2:4, or 1:2.

In compound II, we have 4 grams of A combined with 12 grams of B. To find the ratio of the mass of A to B in compound II, we divide the mass of A by the mass of B:

4g A / 12g B

Simplifying this ratio gives us:

1/3

Therefore, the ratio of the mass of A to B in compound II is 1:3.

Now, we compare the ratio of the masses of A to B in compound II with the ratio in compound I. We see that the ratio in compound II is different from the ratio in compound I.

Since the ratio in compound II is 1:3, we can conclude that the formula of compound II is A1B3.