With reference to 'Silver articles', which of the following statements is/are correct?

Question

With reference to 'Silver articles', which of the following statements is/are correct?

1. Silver articles turn black after some time when exposed to air.

2. It happens due to coating of silver sulphide.

Select the correct answer from the code given below:

1. A. Only 2
2. B. Neither 1 nor 2
3. C. Both 1 and 2 (Correct answer)
4. D. Only 1

Correct Answer

Option C — Both 1 and 2

Detailed Solution & Explanation

The correct answer is Both 1 and 2.

Key Points

• Statement 1 is correct. Silver articles lose their shine and turn black on prolonged exposure to air. This is tarnishing, a form of corrosion.
• Statement 2 is correct. The black coating is silver sulphide (Ag₂S), formed when silver reacts with hydrogen sulphide (H₂S) present in trace amounts in air.
• Both are right, giving option (c).

Additional Information

• Reaction: 2Ag + H₂S → Ag₂S + H₂. Tarnish is a surface phenomenon, unlike the rusting of iron which eats progressively into the metal.
• Compare the standard set of metal-corrosion facts:
  • Copper turns green on exposure to moist air, forming basic copper carbonate.
  • Iron rusts to hydrated iron(III) oxide — needs both air and moisture.
  • Aluminium forms a thin, adherent oxide layer that *protects* the metal beneath.
• Tarnished silver is cleaned by treating it with aluminium foil in baking soda solution, which reduces Ag₂S back to silver.