Question

Which of the following reactions cannot occur?

• A. $2{AgNO}_3\left(aq\right)+Fe\left(s\right)\to Fe{\left({NO}_3\right)}_2\left(aq\right)+2Ag\left(s\right)$
• B. ${CuSO}_4\left(aq\right)+Zn\left(s\right)\to {ZnSO}_4\left(aq\right)+Cu\left(s\right)$
• C. ${CuSO}_4\left(aq\right)+2Ag\left(s\right)\to {Ag}_2{SO}_4\left(aq\right)+Cu\left(s\right)$
• D. $2{AgNO}_3\left(aq\right)+Zn\left(s\right)\to Zn{\left({NO}_3\right)}_2\left(aq\right)+2Ag\left(s\right)$

Answer 1

The correct option is C

${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)\to {\mathrm{Ag}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

The explanation for correct option C:

• Arrangement of the metals on the basis of their reactivity towards other elements is termed as activity series. The activity series in decreasing order is:

$\mathrm{K}>\mathrm{Na}>\mathrm{Li}>\mathrm{Ba}>\mathrm{Sr}>\mathrm{Ca}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Mn}>\mathrm{Zn}>\mathrm{Cr}>\mathrm{Fe}>\mathrm{Cd}>\mathrm{Co}>\mathrm{Ni}>\mathrm{Sn}>\mathrm{Pb}>\mathrm{H}>\mathrm{Sb}>\mathrm{Bi}>\mathrm{Cu}>\mathrm{Hg}>\mathrm{Ag}>\mathrm{Au}>\mathrm{Pt}$

• Elements at the starting of this series are comparatively more reactive than elements present after them in the series.
• In a single displacement reaction, an element from its compound is substituted by another element to form two product molecules. Elements that are more reactive according to the activity series can displace the elements less reactive than them from their compounds.
• Since Silver $\left(\mathrm{Ag}\right)$ is less reactive than Copper $\left(\mathrm{Cu}\right)$ in the activity series, Silver $\left(\mathrm{Ag}\right)$ cannot displace Copper $\left(\mathrm{Cu}\right)$ from Copper sulphate $\left({\mathrm{CuSO}}_4\right)$. Hence, the reaction between Silver $\left(\mathrm{Ag}\right)$ and Copper sulphate will not occur.

${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)\to \mathrm{No}\mathrm{reaction}$

The explanation for incorrect options:

A

• Since Iron $\left(\mathrm{Fe}\right)$ is more reactive Silver $\left(\mathrm{Ag}\right)$ in the activity series, Iron can displace Silver $\left(\mathrm{Ag}\right)$ from Silver nitrate $\left({\mathrm{AgNO}}_3\right)$. Hence, the reaction between Iron and Silver nitrate will occur.

$2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)+\mathrm{Fe}\left(\mathrm{s}\right)\to \mathrm{Fe}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)$

B

• Since Zinc $\left(\mathrm{Zn}\right)$ is more reactive Copper in the activity series, Zinc can displace Copper from Copper sulfate $\left({\mathrm{CuSO}}_4\right)$ . Hence, the reaction between Zinc and Copper sulfate will occur.

${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+\mathrm{Zn}\left(\mathrm{s}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

D

• Since Zinc is more reactive Silver in the activity series, Zinc can displace Silver from Silver nitrate. Hence, the reaction between Zinc and Silver nitrate will occur.

$2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)+\mathrm{Zn}\left(\mathrm{s}\right)\to \mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right)$

Final Answer: Hence, option C is correct.