Answer : The reaction not spontaneous is:
[tex]Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)[/tex]
Explanation :
The given reactions are the examples of single displacement reactions.
Single displacement reactions : It is defined as the reactions in which most reactive metal displaces the least reactive metal from its chemical reaction. The reactivity of metals is given by the series known as reactivity series.
That means the metals that lie above in the series can replace the metals which lie low in the reactivity series.
For the given options:
Option A :
[tex]Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)[/tex]
Copper lies low in the series than hydrogen and hence is less reactive. So, it will not displace hydrogen. Thus, this is a non-spontaneous reaction.
Option B :
[tex]Mg(s)+2HCl(aq)\rightarrow MgCl_2(aq)+H_2(g)[/tex]
Magnesium lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.
Option C :
[tex]2Ni(s)+H_2SO_4(aq)\rightarrow Ni_2SO_4(aq)+H_2(g)[/tex]
Nickel lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.
Option D :
[tex]2Al(s)+6HBr(aq)\rightarrow 2AlBr_3(aq)+3H_2(g)[/tex]
Aluminum lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.
Option E :
[tex]Zn(s)+2HI(aq)\rightarrow ZnI_2(aq)+H_2(g)[/tex]
Zinc lies above in the series than hydrogen and hence is more reactive. So, it will easily displace hydrogen. Thus, this is a spontaneous reaction.
Hence, the reaction not spontaneous is:
[tex]Cu(s)+2HCl(aq)\rightarrow CuCl_2(aq)+H_2(g)[/tex]
