1. The problem statement, all variables and given/known data How many ions are present in 1 formula unit of HI(aq)? HBr(g)? N2S5? 2. Relevant equations These two questions have the same concept, I believe. I went the simple way and thought the answer was 2 for both of them, but apparently that was wrong. Can someone show me how to do this, please? 3. The attempt at a solution Does it have something to do with these compounds being consisted of diatomic molecules? HI(aq) is 2, but HBr(g) is not 2. I'm guessing it has something to do with the fact that one is aq and the other is a gas, but how does that affect it? How many ions would HBr(g) have? And the N2S5 one is not 7 ions. Why? I am confused. Please help!