The pH level of a substance can be determined by the formula pH = –log[H+], where [H+] is the hydrogen ion concentration in moles per liter. An alkaline substance has a pH level between 7 and 14. Which ion concentration corresponds to an alkaline substance?

For pH = −log[H+], a pH between 7 and 14 corresponds to a hydrogen ion concentration between 10⁻⁷ and 10⁻¹⁴ moles per liter. For choice B, −log(5.0 × 10⁻¹²) is about 11.3, which is in the alkaline range. Choice A has a pH above 14, while C and D have pH levels of 7 and about 4, respectively.

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