Which of the following processes does not involved oxidation of iron?

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Questions Match

1.
Which of the following processes does not involved oxidation of iron?

1. Liberation of H2 from steam by iron at high temperature2. Rusting of iron sheets3. Decolourisation of blue CuSO4 solution by iron4. Formation of blue CuSO4 solution by iron

Which of the following processes does not involved oxidation of iron?