Question

select the correct answer.
a displacement reaction takes place when calcium is placed in a solution of zinc chloride. which substances will most likely be produced by the reaction?
ca + zncl₂ → ?

a. zn and cacl₂
b. cazn and o₂
c. cacl and zncl
d. ca, zn, and cl₂

Explanation:

In a displacement reaction, a more reactive metal displaces a less reactive metal from its compound. Calcium (Ca) is more reactive than zinc (Zn). So, Ca will displace Zn from zinc chloride ($\ce{ZnCl_{2}}$). The reaction is a single - displacement reaction of the form $\ce{Metal1 + Salt of Metal2 -> Salt of Metal1 + Metal2}$. So the reaction $\ce{Ca + ZnCl_{2} -> Zn + CaCl_{2}}$ (since Ca has a +2 oxidation state and will form $\ce{CaCl_{2}}$ with chloride ions which have a - 1 oxidation state). Option A shows Zn (displaced metal) and $\ce{CaCl_{2}}$ (salt of the more reactive metal), which fits the displacement reaction. Option B is incorrect as there is no oxygen involved in a simple metal - metal displacement from a metal chloride. Option C has incorrect products as the reaction should form $\ce{CaCl_{2}}$ (not CaCl) and Zn (not ZnCl). Option D is incorrect as Ca is the reactant and should be consumed, and there is no reason for $\ce{Cl_{2}}$ to be a product in this displacement reaction.

Answer:

A. Zn and $\ce{CaCl_{2}}$