Brass gets discoloured in air because of the presence of which of the following gases in air ________ ?
Correct answer: D. Hydrogen sulphide
- A. Carbon dioxide
- B. Oxygen
- C. Nitrogen
- D. Hydrogen sulphide
Explanation
Hydrogen sulphide reacts with the copper and zinc components of brass, producing dark sulphide compounds that discolour its surface. Oxygen and nitrogen are normal air components but are not the specific cause intended here.
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