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MCAT Chemistry Questions — Iron Production

  • by Kerry Goldstein
  • Jan 19, 2015
  • MCAT Blog, MCAT Chemistry, MCAT Question of the Day

Fe2+ is reduced to Fe using a current of 4 A for a total time of 96.5 seconds. How much iron metal will be produced in this time?

A) 10-6 g

B) 10-1 g

C) 102 g

D) 106 g

 

 

Explanation

This question requires your understanding of metal formation through a chemical reduction. In this case, Fe2+ + 2 e–  –> Fe. To determine the amount of iron that is produced in a given time provided the current, you must use Faraday’s constant and the molecular weight, as follows:

(4 C/s)(96.5 s)(1 mole e/96,500 C)(1 mole Fe/2 mole e)(55.8 g Fe/mole Fe) = 10-1 g

If you were unsure of how to go about solving for the iron produced, you may want to consider using dimensional analysis so that you can cancel out all units until you are left with grams of iron. B is the correct answer.

 

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