Mass Chemistry Exam Help?

8. Which of the following metal ions form sulfate compounds that are insoluble in water? A. K+ and Ba2+ B. Ag+ and Mg2+ C. K+ and Ag+ D. Ba2+ and Pb2+ E. Ag+, Mg2+, and Pb2+ The answer is D, but im not sure how to get the answer. How do i know whether it will form sulfate compounds? and how do i know if... show more 8. Which of the following metal ions form sulfate compounds that are insoluble in water?

A. K+ and Ba2+
B. Ag+ and Mg2+
C. K+ and Ag+
D. Ba2+ and Pb2+
E. Ag+, Mg2+, and Pb2+

The answer is D, but im not sure how to get the answer. How do i know whether it will form sulfate compounds? and how do i know if it will be insoluble in water without the reference os a colubility curves chart?

15. For silicon atoms, which ionization energy will show an exceptionally large increase over the preceding ionization energy?

A. 2nd
B. 3rd
C. 4th
D. 5th
E. 6th

I know what ionization energy is (the energy needed to remove an electron from a ground state.. right?), but I have no idea what this 2nd, 3rd, 4th is! please explain!

17. Which of the following shows the correct reactivity of an alkali metal with oxygen?

A. Li(s) + O2(g)  LiO2(s)
B. 4K(s) + O2(g)  2K2O(s)
C. K(s) + O2(g)  KO2(s)
D. 4Na(s) + O2(g)  2Na2O(s)
E. 2K(s) + O2(g)  2KO(s)

To me B and D both look logical!!
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