Chemistry Help?

Question

Explain the results in part 9 based on the observations from part 6 to part 8.

So in part 6, I had to add 20 mg of sodium sulfate to 2 ml of water. My observations were that sodium sulfate dissolved and the color of the soultion was clear.

In part 7, I had to add 20 mg of barium chloride to 2 ml of water. My observations were the same as for part 6.

In part 7, I had to add 20 mg of barium sulfate to mL of water. My observations were that the barium sulfate did not dissolve causing a precipitate to for at the bottom.

With this in mind, how should I answer the question?