Question

question 16 (5 points)
solid zinc is added to aqueous cobalt chloride. using the metal activity series, which chemical equation reflects this reaction and its outcome?
a) 2zn (s) + 3cocl₂ (aq) → 2zncl₂ (aq) + 3co (s)
b) zn (s) + cocl₂ (aq) → nr
c) 2zncl₂ (aq) + 3co (s) → 3cocl₂ (aq) + 2zn (s)
d) zn (s) + cocl₂ (aq) → zncl₂ (aq) + co (s)

Explanation:

Step1: Recall Metal Activity Series

The metal activity series tells us that a more reactive metal can displace a less reactive metal from its compound in a single - displacement reaction. Zinc (Zn) is more reactive than cobalt (Co). So, zinc will displace cobalt from cobalt chloride.

Step2: Write the Correct Reaction

The reaction is a single - displacement reaction. The general form for the reaction of a metal (M) with a metal chloride ($M'Cl_x$) is $M(s)+M'Cl_x(aq)
ightarrow MCl_x(aq)+M'(s)$ (when M is more reactive than $M'$).
For zinc (Zn) and cobalt chloride ($CoCl_2$), the reaction should be:
$Zn(s)+CoCl_2(aq)
ightarrow ZnCl_2(aq)+Co(s)$
Now let's analyze each option:

• Option A: The coefficients are incorrect. The correct ratio for the reaction between Zn and $CoCl_2$ is 1:1 (for Zn and $CoCl_2$) as seen from the formula of the chlorides (Zn has a + 2 charge, Co has a + 2 charge, so the reaction is 1:1 stoichiometry for Zn and $CoCl_2$).
• Option B: Since Zn is more reactive than Co, a reaction should occur, so "NR" (no reaction) is wrong.
• Option C: This reaction is the reverse of what should happen. It would imply that Co is more reactive than Zn, which is not true.
• Option D: This reaction follows the single - displacement reaction pattern, with Zn displacing Co from $CoCl_2$, and the stoichiometry is correct.

Answer:

D) $Zn (s) + CoCl_2 (aq)
ightarrow ZnCl_2 (aq) + Co (s)$