MCAT General Chemistry Question 269: Answer and Explanation

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Question: 269

1. How long would it take for a 1 L sample of methane to decrease to 1 percent of its original amount from atmospheric oxidation?

  • A. 38 years
  • B. 42 years
  • C. 47 years
  • D. 50 years

Correct Answer: C

Explanation:

C The passage states that the half-life of methane is 7 years. Starting with 100 percent and dividing by 2 for each half-life, six half-lives would leave 1.5 percent of the methane remaining, and seven half-lives would leave 0.8 percent of the methane remaining. Therefore, it would require 42 to 49 years, making answer choice C the correct answer.

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