Final answer:
The pair of reactants that will produce a precipitate when mixed together is HCl(aq) and Pb(NO₃)2(aq), as they will form the insoluble salt PbCl₂, which precipitates.
Step-by-step explanation:
To determine which pair of reactants will produce a precipitate when mixed together, we need to consider the possible products of each reaction and consult solubility rules. The reaction that forms an insoluble product will result in a precipitate. Let's go through the options:
- HCl(aq) and NaOH(aq) will undergo a neutralization reaction to form NaCl(aq) and H₂O(l), with no precipitate forming.
- HCl(aq) and Na₂CO₃(aq) will react to form NaCl(aq), H₂O(l), and CO₂(g), also without forming a precipitate.
- HCl(aq) and Na₂S(aq) will react to form NaCl(aq) and H₂S(g), which does not result in a precipitate.
- HCl(aq) and Pb(NO₃)₂(aq) will react to form PbCl₂(s) and HNO₃(aq). According to solubility rules, PbCl₂ is insoluble in water, so this reaction will produce a precipitate.
Therefore, the correct answer is D) HCl(aq) and Pb(NO₃)₂(aq), as the products include an insoluble salt, PbCl₂, which precipitates from the solution.