Answer:
S²⁻(aq) + Cr²⁺(aq) ⇄ CrS(s)
Explanation:
The molecular equation includes all the species in the molecular form. Usually, it is useful to write this first to balance the equation. This is a double displacement reaction.
K₂S(aq) + Cr(NO₃)₂(aq) ⇄ 2 KNO₃(aq) + CrS(s)
The full ionic equation includes all ions and the species that no dot dissociate in water.
2 K⁺(aq) + S²⁻(aq) + Cr²⁺(aq) + 2 NO₃⁻(aq) ⇄ 2 K⁺(aq) + 2 NO₃⁻(aq) + CrS(s)
The net ionic equation includes only those ions that participate in the reaction and the species that do not dissociate in water.
S²⁻(aq) + Cr²⁺(aq) ⇄ CrS(s)