Answer: The correct answer is Option 1 and Option 2.
Explanation:
Redox reactions are termed as the reactions in which reduction and oxidation reactions occur simultaneously.
Reduction reactions are the ones where a substance gains electrons. The oxidation state of the substance gets reduced.
Oxidation reactions are the ones where a substance looses electrons. The oxidation state of the substance is increased.
All the given reactions are a type of single displacement reactions. In this, a more reactive metal displaces a less reactive metal from its chemical reaction. The reactivity is determined from a series known as reactivity series. A metal which lies above in the series is more reactive than the metals which lie below in the series.
\(A+BC\rightarrow AC+B\)
From the given options:
Option 1: \(Ni(s)+Pb^{2+}(aq.)\rightarrow Ni^{2+}(aq.)+Pb(s)\)
Here, nickel lies above in the series than lead. Thus, it will easily replace lead from its chemical reaction.
Option 2: \(Al(s)+3Ag^+(aq.)\rightarrow Al^{3+}(aq.)+3Ag(s)\)
Here, aluminium lies above in the series than silver. Thus, it will easily replace silver from its chemical reaction.
Option 3: \(Ni(s)+Zn^{2+}(aq.)\rightarrow Ni^{2+}(aq.)+Zn(s)\)
Here, nickel lies below in the series than zinc. Thus, it will not easily replace zinc from its chemical reaction.
Option 4: \(Fe^{2+}(aq.)+Cd(s)\rightarrow Fe(s)+Cd^{2+}(aq.)\)
Here, cadmium lies below in the series than iron. Thus, it will not easily replace iron from its chemical reaction.
Thus, the correct answer is Option 1 and Option 2.
