Question

The pH of a cup of black coffee is 5 while the pH of glass of tomato juice is 4. Comparing the pH of the two liquids, the tomato juice has _______________ [H+] than the coffee.

A) half as many
B) 10 times more
C) 10 times less
D) 100 times more

Answer 1

The pH scale is a logarithmic scale of acidity based on the concentration of hydronium ions [H3O+]. Each 1 step smaller indicates a ten times increase in [H3O+] concentration; for example, take a solution with a pH of 6, a solution with a pH of 7, and another solution with a pH of 8. The pH 6 solution has a ten times greater concentration of [H3O+] than the pH 7, and a 100 times greater concentration than the pH 8.

This means that the tomato juice with a pH of 4 will have B, ten times the concentration of the coffee with a pH 5.

Answer 2

Answer: THE ANSWER IS B!!

Explanation: Comparing the pH of the two liquids, the tomato juice has 10 times more [H+] than the coffee. Another way to represent the [H+] of the two liquids is: coffee = 1 X 10-5 and tomato juice = 1 X 10-4. You can then see that tomato juice has 10 times more [H+].