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:
The task is to calculate water hardness in ppm after converting MgCl₂ into CaCO₃ equivalent.

Step 2: Key Formula or Approach:
Determine the equivalent mass of CaCO₃ using the molar mass ratio and calculate ppm using the sample mass.

Step 3: Detailed Explanation:
The equivalent hardness due to 19 mg of MgCl₂ is \(19\times100/95=20\) mg of CaCO₃. Dividing this by the 2 kg water sample gives 10 mg/kg. As mg/kg is equal to ppm for water, the hardness is 10 ppm.

Step 4: Final Answer:
The water hardness is 10 ppm.