Question

A student has been collecting silver coin and copper coin. after some days when she took out the coin to count she observed a black coating a black coating on silver coin and green write the chemical reaction involve

Answer 1

2Cu(s) + \displaystyle \frac{1}{2}​2​​1​​O2(g) ⟶ Cu2O(s)        (red)
Cu2O(s) + \displaystyle \frac{1}{2}​2​​1​​O2(g) ⟶ 2CuO(s)     (black)