Question

use the activity series below to predict whether the following reactions will take place.
li > k > ba > sr > ca > na > mg > al > mn > zn > cr > fe > cd >
co > ni > sn > pb > h > sb > bi > cu > ag > pd > hg > pt > au
ca + znbr₂ → cabr₂ + zn
cu + 2kno₃ → cu(no₃)₂ + 2k

Explanation:

For the reaction $\boldsymbol{\ce{Ca + ZnBr_2

ightarrow CaBr_2 + Zn}}$:

Step1: Check activity series positions

In the given activity series, $\ce{Ca}$ is positioned before $\ce{Zn}$ (i.e., $\ce{Ca > Zn}$).

Step2: Apply single - displacement rule

For a single - displacement reaction of the form $\ce{A + BC
ightarrow AC + B}$, the reaction occurs if the metal $\ce{A}$ is more reactive than the metal $\ce{B}$ in the compound $\ce{BC}$. Since $\ce{Ca}$ is more reactive than $\ce{Zn}$ (as per the activity series), the reaction $\ce{Ca + ZnBr_2
ightarrow CaBr_2 + Zn}$ will take place.

For the reaction $\boldsymbol{\ce{Cu + 2KNO_3

ightarrow Cu(NO_3)_2 + 2K}}$:

Step1: Check activity series positions

In the activity series, $\ce{K}$ is positioned before $\ce{Cu}$ (i.e., $\ce{K > Cu}$).

Step2: Apply single - displacement rule

For the reaction $\ce{Cu + 2KNO_3
ightarrow Cu(NO_3)_2 + 2K}$, we are trying to see if $\ce{Cu}$ can displace $\ce{K}$ from $\ce{KNO_3}$. But since $\ce{K}$ is more reactive than $\ce{Cu}$, $\ce{Cu}$ cannot displace $\ce{K}$ from its compound. So the reaction $\ce{Cu + 2KNO_3
ightarrow Cu(NO_3)_2 + 2K}$ will not take place.

Answer:

s:

• For $\ce{Ca + ZnBr_2

ightarrow CaBr_2 + Zn}$: The reaction will take place.

• For $\ce{Cu + 2KNO_3

ightarrow Cu(NO_3)_2 + 2K}$: The reaction will not take place.