Which of the following produces black spots when it comes in contact with organic substances such as skin and cellulose?
Correct answer: B. AgNO3
- A. CuSO4
- B. AgNO3
- C. K2MnO4
- D. CH3COOH
Explanation
AgNO3 produces black spots on skin and cellulose because light or organic matter reduces Ag+ to finely divided metallic silver, which appears black or dark grey. The likely mistake is choosing CuSO4 because copper salts are coloured, but copper sulfate does not characteristically form black stains in this test.
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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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