Which of the following salts is the most acidic

Question

in aqueous solutions?
1. KBr
2. NaI
3. Al(NO3)3
4. BaCl2
5. AgNO3
6. Fe(NO3)2
7. Pb(NO3)2

Answer 1

I don't know the Ka values but I suspect Al(NO3)3; however I looked up the Ka values and Fe is about 10^-3 and Al is about 10^-5 so Fe(NO3)3 is a sronger acid than Al(NO3)3.