Question

Which of the following when added to water will cause a significant change in the pH of the solution?
1 NH4HSO4
2 (NH4)2SO4
3 Na2SO4


I believe the answer is 1 & 2. is that right.

Answer 1

I think the secret word here is significant.
Yes, 1 will do it.
Although a solution of 2 will be acidic, I don't think it is nearly as acidic as 1. Whereas 1 might change pure water from pH 7.0 to about 1 or 2, #2 probably won't change much more than 7.0 to 5.0.
3 is not acidic at all.