Multiple choice

Name plates made of brass get discolored in air because of the presence of which of the following gases in the air?

  1. Oxygen

  2. Nitrogen

  3. Carbon dioxide

  4. Hydrogen sulphide
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hydrogen sulphide (H2S) reacts with copper in brass to form black copper sulphide, causing discoloration. Oxygen and nitrogen don't react noticeably with brass under normal conditions. Carbon dioxide doesn't significantly tarnish brass compared to H2S's strong reaction with copper.

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