Question

question 4 (2 points)
which of the following is a precipitation reaction?
mg (s) + 2hcl (aq) → mgcl2 (aq) + h2 (g)
naoh (aq) + hno3 (aq) → h2o (l) + nano3 (aq)
none of these
hcl (aq) + lioh (aq) → licl (aq) + h2o (l)
pb(c2h3o2)2 (aq) + 2 nacl (aq) → pbcl2 (s) + 2 nac2h3o2 (aq)

Explanation:

A precipitation reaction forms an insoluble solid (precipitate) from two aqueous - phase reactants. In the reaction $\text{Pb}(\text{C}_2\text{H}_3\text{O}_2)_2(\text{aq})+2\text{NaCl}(\text{aq})
ightarrow\text{PbCl}_2(\text{s}) + 2\text{NaC}_2\text{H}_3\text{O}_2(\text{aq})$, $\text{PbCl}_2$ is a solid precipitate. The other reactions do not form a solid product. The first is a single - displacement reaction, the second and fourth are acid - base neutralization reactions.

Answer:

$\text{Pb}(\text{C}_2\text{H}_3\text{O}_2)_2(\text{aq})+2\text{NaCl}(\text{aq})
ightarrow\text{PbCl}_2(\text{s}) + 2\text{NaC}_2\text{H}_3\text{O}_2(\text{aq})$