Q. Copper substances when exposed to air gains a green coating due to the formation of:
Answer: CuCO3.Cu(OH)2
Notes: When copper is exposed to air, it reacts with moist carbon dioxide in the air and slowly loses its shiny brown surface and gains a green coat. This green substance is basic copper carbonate (CuCO3. Cu(OH)2). The formation of this green coating on the surface of a copper object corrodes it.

• Cu + H2O(g) + CO2 —> [CuCO3.Cu(OH)2]

This question is part of 40000+ General Studies MCQ Series Course on GKToday Android app. Question Number: 99 in Chemistry-17-Important Metals in above course in App.