When SO2 solution is passed over which of the following it turns green?
Correct answer: A. K2Cr2O7
- A. K2Cr2O7
- B. H2SO4
- C. SO3
- D. P2O5
Explanation
SO2 is a reducing agent and reduces orange dichromate ions, Cr2O7^2-, to green Cr3+ ions in acidic solution. Therefore K2Cr2O7 changes colour to green. The likely wrong choice is H2SO4, because students may focus on the acidic medium required for the reaction rather than on the substance that undergoes reduction.
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About Redox Reactions
Redox reactions involve oxidation and reduction occurring together, with electrons transferred between species or oxidation numbers changing. The topic covers assigning oxidation states, identifying oxidizing and reducing agents, balancing redox equations by oxidation number or half-reaction methods, and connecting chemical changes with galvanic and electrolytic cells.
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