Question

Of the four reactions you observed, which was already balanced?
Group of answer choices

CuCl2 + Al --> Cu + AlCl3

Mg + O2 --> MgO

HCl + Zn --> H2 + ZnCl2

CuCO3 --> CO2 + CuO

Answer 1

CuCO3 → CO2 + CuO

Explanation: atoms on each side — Cu:1, C:1, O:3 — so the equation is already balanced.