The poster’s chemical formula was wrong, it should be Cu2(OH)2CO3

1. The relative molecular mass of basic copper carbonate:

64×2 ( 16 1)×2 12 16×3

=222

2. The mass ratio of each element in basic copper carbonate: (m represents mass)

m(Cu)：m(O)：m(H)：m(C)=64×2：16×5：1×2：12×1

That is

Copper: Oxygen: Hydrogen: Carbon = 128: 80: 2: 12

=64: 40: 1: 6

3. Mass fraction of oxygen element in basic copper carbonate:

(16×5)÷222≈36.04

Answer: (1) The relative molecular mass of basic copper carbonate is 222;

(2) Basic copper carbonate The mass ratio of copper, oxygen, hydrogen and carbon elements in copper carbonate is 64:40:1:16;

(3) The mass fraction of oxygen element in basic copper carbonate is approximately 36.04.