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JAMB Chemistry 2005 Question 4

Question 4

Energy Changes

When iron is exposed to moisture and it rusts, the value of ΔG for the reaction is

  1. A.neutral
  2. B.zero
  3. C.positive
  4. D.negative
Show the answer and explanation

Answer: D (negative)

Explanation

A reaction that takes place spontaneously has a negative free-energy change (ΔG below zero). Iron rusts by itself in moist air, so ΔG is negative.