MCAT General Chemistry Question 42: Answer and Explanation

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Question: 42

12. In the structure shown, which atom(s) have the most positive charge?

  • A. The phosphorus atom has the most positive charge.
  • B. All atoms share the charge equally.
  • C. The four oxygens share the highest charge.
  • D. The oxygen at the peak of the trigonal pyramidal geometry has the most positive charge.

Correct Answer: A

Explanation:

In this Lewis diagram, the phosphate molecule has an overall formal charge of -3. The four oxygens would each be assigned a formal charge of -1. Given the overall charge of -3 and the -1 charge on each oxygen, the phosphorus must have a formal charge of +1.

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