Question

which could be true about an unknown sample with a ph of 7? it contains only water. it is highly acidic. it has a very high hydroxide ion concentration. it is a solution of hf and water.

Explanation:

A pH of 7 indicates a neutral solution. Pure water has a pH of 7. Acidic solutions have pH < 7, basic solutions (with high hydroxide - ion concentration) have pH > 7, and HF is an acid so its solution with water is acidic.

Answer:

It contains only water.