In which chemical equation is the number of atoms in the reactants the same as the number of atoms in the products?

Question

1. CO2 + H20 -- CH2OH + O2
2. CH4 + O2 -- CO2 + 2H2O
3. Li2CO3 -- LiO + CO2
4. Zn + 2HCI -- H2 + ZnCl2

Answer 1

In option 4, Zn + 2HCI -- H2 + ZnCl2, the number of atoms in the reactants (Zn and 2HCI) is the same as the number of atoms in the products (H2 and ZnCl2).