AP Environmental Science

Answer: B - The pH of water is 7.

Key Takeaway: By measuring the concentration of hydronium ions, pH is generally used to determine if a given solution is an acid or a base. This can be done using a pH indicator, which will change color around a particular pH level. Pure water should have a pH around 7. When an acid is dissolved into the water, the pH will become lower than 7 (down to 0); when a base is dissolved into the water, the pH will become greater than 7 (up to 14).