Question

What is the ratio of Al3+ ions to S2- ions in a neutral compound?
A. 1:1
B 2:1
C.2:3
D. 3:2

Answer 1

Let the number of \(Al^{3+}\) be x and let the number of \(S^{2-}\) ions be y.

Then their charges times their number of atoms must be 0

\((+3)x+(-2)y=0\)

To avoid math, you can just "cross" their charges to be their coefficients, let me illustrate:




so you end up with \(Al_2S_3\)

This makes sense because 2 \(Al^{3+}\) is 6+ and 3 \(S^{2-}\) are -6

This adds up to 0

Answer 2

@aaronq so it would be A. Correct?

Answer 3

no, the ratio is the number of atoms - i.e. their coefficients