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

Question

A. The substance with the lower pH has 1,000 times as many hydrogen ions per volume of water
B. The substance with the higher pH has twice as many hydrogen ions per volume of water
C. The substance with the higher pH has 1,000 time as many ions per volume of water
D. The substance with the lower pH has twice as many hydrogen ions per volume of water

Answer 1

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

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

Here's the reasoning:

The pH scale is logarithmic, meaning each whole number change on the scale represents a tenfold change in hydrogen ion concentration. Therefore:

• A substance with a pH of 3.0 has a hydrogen ion concentration of ${10}^{-3}$ M.
• A substance with a pH of 6.0 has a hydrogen ion concentration of ${10}^{-6}$ M.

To find the difference in hydrogen ion concentration:

$$\frac{{10}^{-3}}{{10}^{-6}}={10}^3=1000$$

This shows that the substance with a pH of 3.0 has 1,000 times as many hydrogen ions as the substance with a pH of 6.0.