A chemist has a bottle of concentrated and another with dilute sulfuric acid. Which has highest pH?

pH scale is from 1-14. 1 is the most acidic anything can be, and 14 is the most basic anything can be. 7 is neutral. Since the concentrated acid is more acidic than the dilute acid, it has a pH closer to 1. In terms of acidity on the pH scale, less is more. And vice versa for bases.