Which of the following redox reactions do you expect to occur spontaneously in the forward direction?

check all that apply.

ni(s)+pb2+(aq)→ni2+(aq)+pb(s)
al(s)+3ag+(aq)→al3+(aq)+3ag(s)
ni(s)+zn2+(aq)→ni2+(aq)+zn(s)
fe2+(aq)+cd(s)→fe(s)+cd2+(aq)

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.

From the given options:

Option 1:

Here, nickel lies above in the series than lead. Thus, it will easily replace lead from its chemical reaction.

Option 2:

Here, aluminium lies above in the series than silver. Thus, it will easily replace silver from its chemical reaction.

Option 3:

Here, nickel lies below in the series than zinc. Thus, it will not easily replace zinc from its chemical reaction.

Option 4:

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.