Certain types of chemical reactions result in the formation of an insoluble product, known as a precipitate. These reactions are called precipitation reactions. To determine whether a particular reaction is a precipitation reaction, we can use solubility rules to identify if any of the products are insoluble in water.
Let's analyze each equation step by step to identify if they are precipitation reactions:
1. [tex]\(Na_2S + FeBr_2 \rightarrow 2 NaBr + FeS\)[/tex]
- The products are sodium bromide ([tex]\(NaBr\)[/tex]) and iron sulfide ([tex]\(FeS\)[/tex]).
- Sodium bromide ([tex]\(NaBr\)[/tex]) is soluble in water.
- Iron sulfide ([tex]\(FeS\)[/tex]) is generally insoluble in water.
- Since [tex]\(\text{FeS}\)[/tex] is an insoluble product, this reaction is a precipitation reaction.
2. [tex]\(MgSO_4 + CaCl_2 \rightarrow MgCl_2 + CaSO_4\)[/tex]
- The products are magnesium chloride ([tex]\(MgCl_2\)[/tex]) and calcium sulfate ([tex]\(CaSO_4\)[/tex]).
- Magnesium chloride ([tex]\(MgCl_2\)[/tex]) is soluble in water.
- Calcium sulfate ([tex]\(CaSO_4\)[/tex]) is slightly soluble and often considered insoluble in water.
- Since [tex]\(\text{CaSO_4}\)[/tex] is an insoluble product, this reaction is a precipitation reaction.
3. [tex]\(LiOH + NH_4I \rightarrow LiI + NH_4OH\)[/tex]
- The products are lithium iodide ([tex]\(LiI\)[/tex]) and ammonium hydroxide ([tex]\(NH_4OH\)[/tex]).
- Both lithium iodide ([tex]\(LiI\)[/tex]) and ammonium hydroxide ([tex]\(NH_4OH\)[/tex]) are soluble in water.
- Since all products are soluble, this reaction is not a precipitation reaction.
4. [tex]\(2 NaCl + K_2S \rightarrow Na_2S + 2 KCl\)[/tex]
- The products are sodium sulfide ([tex]\(Na_2S\)[/tex]) and potassium chloride ([tex]\(KCl\)[/tex]).
- Both sodium sulfide ([tex]\(Na_2S\)[/tex]) and potassium chloride ([tex]\(KCl\)[/tex]) are soluble in water.
- Since all products are soluble, this reaction is not a precipitation reaction.
5. [tex]\(AgNO_3 + NaCl \rightarrow AgCl + NaNO_3\)[/tex]
- The products are silver chloride ([tex]\(AgCl\)[/tex]) and sodium nitrate ([tex]\(NaNO_3\)[/tex]).
- Sodium nitrate ([tex]\(NaNO_3\)[/tex]) is soluble in water.
- Silver chloride ([tex]\(AgCl\)[/tex]) is insoluble in water.
- Since [tex]\(\text{AgCl}\)[/tex] is an insoluble product, this reaction is a precipitation reaction.
Based on this analysis, the equations that represent precipitation reactions are:
1. [tex]\(Na_2S + FeBr_2 \rightarrow 2 NaBr + FeS\)[/tex]
2. [tex]\(MgSO_4 + CaCl_2 \rightarrow MgCl_2 + CaSO_4\)[/tex]
5. [tex]\(AgNO_3 + NaCl \rightarrow AgCl + NaNO_3\)[/tex]
Thus, the correct answers are equations 1, 2, and 5.
