Question

Tarnishing of silver is due to formation of

• A. Its sulphate layer
• B. Its nitrate layer
• C. Its sulphide layer
• D. Its chloride layer

Hint:

Remember the colors of common corrosion products:
- Iron \(\rightarrow\) Reddish-brown rust (hydrated iron(III) oxide).
- Copper \(\rightarrow\) Greenish-blue patina (copper carbonate/sulfate).
- Silver \(\rightarrow\) Black tarnish (silver sulfide).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We are asked to identify the chemical compound that forms on silver, causing it to tarnish (turn black).

Step 2: Key Formula or Approach:
This is a factual question about the corrosion of silver. Tarnishing is the chemical reaction between silver and sulfur compounds present in the atmosphere.

Step 3: Detailed Explanation:
Silver (Ag) is a relatively unreactive metal but is susceptible to reaction with sulfur compounds. The atmosphere contains trace amounts of hydrogen sulfide (H\(_2\)S), which originates from pollution and biological decay.
Silver reacts with H\(_2\)S in the presence of oxygen to form a black layer of silver sulfide (Ag\(_2\)S). This layer is the tarnish.
The reaction is:
\[ 4\text{Ag}(s) + 2\text{H}_2\text{S}(g) + \text{O}_2(g) \rightarrow 2\text{Ag}_2\text{S}(s) + 2\text{H}_2\text{O}(l) \]
This black silver sulfide layer obscures the metal's luster.

Step 4: Final Answer:
Tarnishing of silver is due to the formation of its sulphide layer.