The presence of which of the following gases in air makes Brass discoloured?

Options :
  1. Carbon dioxide
  2. Oxygen
  3. Hydrogen sulphide
  4. Nitrogen
Answer and Explanation :-

Answer: Option 3


Brass is an alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. Corrosion and rust may appear the same, however they are very different. Brass is not prone to rusting but is susceptible to corrosion. If the zinc content in the brass is higher, the rate of corrosion can be minimized but not eliminated completely. Air exposure corrodes brass over time. The oxidation turns brass into almost black and altogether spoils the overall beauty of the furniture, musical instrument, or jewel. Hydrogen sulfide is the chemical compound with the formula H2S. It is a colorless gas with the characteristic foul odor of rotten eggs; it is heavier than air, very poisonous, corrosive, flammable and explosive. H2S is corrosive to some metals under some conditions (e.g. moisture and temperature). Wet or moist H2S is corrosive to copper, brass, bronze, cast iron and steel. It can tarnish silverware and discolour copper and brass utensils. Hydrogen sulfide also can cause yellow or black stains on kitchen and bathroom fixtures.

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