Question

in which reaction is precipitation occurring?
a. mgcl₂(aq) + cuso₄(aq) → cucl₂(aq) + mgso₄(aq)
b. cdso₄(aq) + k₂s(aq) → cds(s) + k₂so₄(aq)
c. naoh(aq) + nh₄cl(aq) → nacl(aq) + nh₄oh(aq)
d. k₂so₄(aq) + naoh(aq) → k₂oh(aq) + naso₄(aq)
e. hno₃(aq) + koh(aq) → kno₃(aq) + h₂o(l)

Explanation:

To determine which reaction has precipitation, we check if a solid (s) product forms.

• Option A: All products are aqueous, no precipitate.
• Option B: \( \text{CdS}(s) \) is a solid precipitate (sulfides of Cd are insoluble).
• Option C: All products are aqueous ( \( \text{NH}_4\text{OH} \) is aqueous, actually \( \text{NH}_3\cdot\text{H}_2\text{O} \) ), no precipitate.
• Option D: Products are not valid (formulas incorrect, and no solid).
• Option E: This is a neutralization reaction forming water and aqueous salt, no precipitate.

Answer:

B. \( \text{CdSO}_4(\text{aq}) + \text{K}_2\text{S}(\text{aq})
ightarrow \text{CdS}(\text{s}) + \text{K}_2\text{SO}_4(\text{aq}) \)