Which statement best describes the difference between a substance with a pH of 3.0 and a substance with a pH of 6.0?

Question

The substance with the lower pH has 1,000 times as many hydrogen ions per volume of water.

The substance with the lower pH has twice as many hydrogen ions per volume of water. 
 
The substance with the higher pH has twice as many hydrogen ions per volume of water.

The substance with the higher pH has 1,000 times as many hydrogen ions per volume of water.

GPT-4o mini · Answer

The best statement that describes the difference between a substance with a pH of 3.0 and a substance with a pH of 6.0 is:

The substance with the lower pH has 1,000 times as many hydrogen ions per volume of water.

Here's why: pH is a logarithmic scale, specifically based on the concentration of hydrogen ions ( $H^{+}$ ). For every one unit change in pH, the concentration of hydrogen ions changes by a factor of 10. Therefore, a solution with a pH of 3.0 has:

$10^{- 3}$ moles of $H^{+}$ per liter, and
A solution with a pH of 6.0 has $10^{- 6}$ moles of $H^{+}$ per liter.

To compare, you take $10^{- 3} / 10^{- 6} = 10^{3} = 1, 000$ . Thus, the substance with a pH of 3.0 has 1,000 times more hydrogen ions than the substance with a pH of 6.0.