chemistry help?

Question

A phosphate buffer (H2PO4-/HPO42-) has a pH of 8.3. Which of the following changes will cause the pH to increase?
dissolving a small amount of Na2HPO4
dissolving a small amount of NaH2PO4
adding a small amount of dilute hydrochloric acid
adding a small amount of dilute phosphoric acid
making the buffer more concentrated by removing some water

Answer 1

dissolving a small amount of Na2HPO4

Reason:
Remember, that adding acid will lower pH, but adding base will increase pH. The buffer is an (weak) acid-(weak) base mixture. In this case H2PO4- is the acid and HPO42- is the base.