Which equation represents an incorrectly balanced chemical equation?

na2co3(s)→na2o(s)+co2(g)

4al(s)+3o2(g)→2al2o3(s)

zn(s)+2hcl(aq)→zncl2(aq)+h2(g)

2zns(s)+2hcl(aq)→4zncl2(aq)+h2s(g)

2ZnS (s)  + 2HCl (aq)  → 4ZnCl₂ (aq)  + H₂S (g)

Explanation:

The last equation is incorrectly  balanced:

2ZnS (s)  + 2HCl (aq)  → 4ZnCl₂ (aq)  + H₂S (g)

In this chemical equation two zinc and sulfur atoms are present in reactant side while in product side four atoms of zinc and one atom of sulfur are present, that's why it is incorrectly balanced.

The other equations:

Na₂CO₃ (s)   →  Na₂O (s)  + CO₂ (g)

It is correctly balanced because two sodium one carbon and three oxygen atoms are present on both side of reaction.

4Al(s)  + 3O₂ (g)  →   2Al₂O₃ (s)

It is correctly balanced because four aluminium and six oxygen atoms are present in reactant and product side.

Zn (s)  + 2HCl (aq)    →  ZnCl₂(aq)   + H₂ (g)

It is correctly balanced because one zinc two chlorine and two hydrogen atoms are present on both side of reaction.

the answer is option a.