Which combination will produce a precipitate? A) NaOH(aq) and HCl (aq) B) NaF (aq) and HCl (aq) C) NaC2H3O2 (aq) and HCl (aq) D) KOH (aq) and Mg(NO3)2 (aq) E) AgNO3(aq) and Ca(C2H302)2 (aq)
The Correct Answer and Explanation is:
The correct answer is: E) AgNO₃(aq) and Ca(C₂H₃O₂)₂(aq).
Explanation (300+ words):
To determine which combination produces a precipitate, we need to consider solubility rules and double displacement (metathesis) reactions, where two aqueous ionic compounds exchange ions. A precipitate forms if the product is insoluble in water.
Let’s briefly evaluate each choice:
A) NaOH(aq) + HCl(aq):
This is a neutralization reaction between a strong base and a strong acid:
NaOH + HCl → NaCl + H₂O
Both NaCl and water are soluble, so no precipitate forms.
B) NaF(aq) + HCl(aq):
This is an acid-base reaction:
NaF + HCl → NaCl + HF
Hydrofluoric acid (HF) is soluble in water. Again, no precipitate forms.
C) NaC₂H₃O₂(aq) + HCl(aq):
This results in acetic acid (HC₂H₃O₂), a weak acid:
NaC₂H₃O₂ + HCl → NaCl + HC₂H₃O₂
All products are soluble, so no precipitate.
D) KOH(aq) + Mg(NO₃)₂(aq):
Double displacement:
2KOH + Mg(NO₃)₂ → 2KNO₃ + Mg(OH)₂
Magnesium hydroxide (Mg(OH)₂) is sparingly soluble and can form a precipitate in sufficient concentration. However, it’s borderline and may not precipitate easily depending on conditions.
E) AgNO₃(aq) + Ca(C₂H₃O₂)₂(aq):
Double displacement:
2AgNO₃ + Ca(C₂H₃O₂)₂ → 2AgC₂H₃O₂ + Ca(NO₃)₂
Here, AgC₂H₃O₂ (silver acetate) is only slightly soluble, and in most typical lab conditions, a precipitate forms.
Silver salts are generally insoluble except for a few (like AgNO₃ and AgF). Silver acetate is known to form a white precipitate, especially at higher concentrations.
Conclusion:
E) AgNO₃ and Ca(C₂H₃O₂)₂ produce a precipitate of AgC₂H₃O₂ due to its low solubility. This reaction best meets the criteria for precipitate formation based on solubility rules.