MCAT General Chemistry Question 164: Answer and Explanation

Test Information

• Use your browser's back button to return to your test results.
• Do more MCAT general chemistry practice tests.

Question: 164

14. After balancing the following oxidation–reduction reaction, what is the sum of the stoichiometric coefficients of all of the reactants and products?

S₈ (s) + NO₃^- (aq) → SO₃^2- (aq) + NO (g)

• A. 4
• B. 50
• C. 91
• D. 115

Correct Answer: D

Explanation:

Utilize the method described earlier to balance this redox reaction. The balanced half-reactions are:

To get equal numbers of electrons in each half-reaction, the oxidation half-reaction will have to be multiplied by 3, and the reduction half-reaction will have to be multiplied by 32:

This makes the overall reaction:3S₈ + 32 NO₃^- + 8 H₂O → 24 SO₃^2- + 32 NO + 16 H⁺