Question

Consider the reactions :
$CuS{O_4} + Fe \to FeS{O_4} + Cu$
$FeS{O_4} + Zn \to ZnS{O_4} + Fe$
(A) Zn is most reactive, Fe is least reactive
(B) Fe is most reactive and Cu is least reactive
(C) Zn is most reactive and Cu is least reactive
(D) Cu is most reactive, Fe is least reactive

Answer 1

Hint: The answer is based on the reactivity of metals which form activity series. The metal on top in reactivity series can displace any metal on its lower side. The metal which is on top is the most reactive while the metal on lower is least reactive.

Complete step by step answer:
There is a reactivity series of metals in which metals are arranged in series from highly reactive to lowest one. The metal which is on top can displace any other metal which is present lower of it in series.
A short series including these metals is as -

Potassium

Sodium

Lithium

Barium

Strontium

Manganese

Zinc

Chromium

Iron

Cadmium

Cobalt

Nickel

Tin

Copper

Mercury

Now, if we series, iron is above copper. Thus, iron can replace copper from the copper sulphate. So, the first reaction is correct.
Further, Zinc is above iron in the activity series. So, the Zinc can displace iron in iron sulphate. So, even the second reaction is correct.
From the complete series, comparing zinc, iron and copper; we see that the zinc is on top of these two. So, the zinc can displace both iron and copper. Thus, zinc is the most reactive.
After, the zinc is iron in reactivity series. So, iron is the second most reactive among these three. At the end is copper. So, it is the least reactive in nature.
Now, if we see the options given to us; the third option says that the Zinc is most reactive and copper is least reactive and this is the correct answer.

So, the option (C) is correct.

Note: It must be noted that reactivity of a compound can be known from valence electrons to some extent. If the valency is one or two then it is easy to accomplish and thus the element is more reactive in nature.