Question

Solution 1 has a pH of 6.5. When Solution 2 is poured into Solution 1, the new solution has a pH of 5.2. What must be true of Solution 2?

Answer 1

The new solution is an average pH of Solution 1 and 2.
(I'm assuming sorry if I'm wrong)
You could also say solution 2 is more acidic and less basic because of the new lower pH.

Answer 2

"Averaging" pH values does not work because they are based on logarithms of [H+] ion. However, can be sure that since solution 2 made the combination more acidic, solution 2 is more acidic than solution 1.