A double displacement reaction is a type of reaction where two reactants exchange ions to form two new compounds. Double displacement reactions typically result in the formation of a product that is a precipitate.
Double displacement reactions take the form:
AB + CD → AD + CB
For the reaction:
Zn(NO₃)₂(aq) + Na₂S(aq) → ZnS(s) + X
If Zn bond with S, NO₃ must be react with Na to produce NaNO₃ that is a soluble salt (Is in aqueous state (aq)). As there are 2 Na and 2 NO₃ the right answer is:
