Question

Referring to an activity series, which of the following combinations of reactants would not produce a successful single-replacement reaction?
Zn +CuSO4
Ca + MgSO4
Ag + SnSO4
K + Na2SO4

Answer 1

 I believe the answer is Ca + MgSO4

Answer 2

Answer: The combination of reactants that will not undergo single displacement reaction is $(Ag+SnSO_4)$

Explanation:

Single-displacement reactions are defined as the reactions in which a more reactive metal displaces a less reactive metal from its chemical reaction. The reactivity of metal is judged by a series known as reactivity series.

$A+BC\rightarrow AC+B$

Metal A is more reactive than metal B.

The metal which is present above in the series is more reactive than the metal which is present below in the series.

For the given options:

Option 1:  $Zn+CuSO_4$

Zinc lies above in the series than copper and thus will easily replace copper from its chemical reaction.

$Zn+CuSO_4\rightarrow ZnSO_4+Cu$

Option 2:  $Ca+MgSO_4$

Calcium lies above in the series than magnesium and thus will easily replace magnesium from its chemical reaction.

$Ca+MgSO_4\rightarrow CaSO_4+Mg$

Option 3:  $Ag+SnSO_4$

Silver lies below in the series than tin and thus will not replace tin from its chemical reaction.

$Ag+SnSO_4\rightarrow \text{No reaction}$

Option 4:  $K+Na_2SO_4$

Potassium lies above in the series than sodium and thus will easily replace sodium from its chemical reaction.

$2K+Na_2SO_4\rightarrow K_2SO_4+2Na$

Hence, the combination of reactants that will not undergo single displacement reaction is $(Ag+SnSO_4)$