Q. 14.5( 4 Votes )

The solutions of ZnSO4, FeSO4, CuSO4, and AgNO3 are taken in four different test tubes. Suppose, an iron nail is kept immersed in each one.

• In which test tube the iron nail undergoes a colour change?

• What is the reaction taking place here?

• Justify your answer. (Refer reactivity series of metals).

Answer :

(i) The iron nail undergoes a colour change in that test tube which has CuSO4 solution.

Since Fe is more reactive than Cu and Ag but less reactive than Zn because in reactivity series Fe is above to Cu and Ag. So, Fe will displace Cu and Ag from their salts. But colour will change in a test tube of CuSO4 solution from blue to green. Because AgNO3 is colourless and Fe(NO3)2 is also colourless so there is no colour change in test tube of AgNO3.


(ii) Fe(s) + CuSO4(aq) FeSO4(aq)+ Cu(s)


(iii) Since Fe is more reactive than Cu and Ag but less reactive than Zn because in reactivity series Fe is above to Cu and Ag. So Fe will displace Cu and Ag from their salts. But colour will change in test tube of CuSO4 solution from blue to green. Because AgNO3 is colourless and Fe(NO3)2 is also colourless so there is no colour change in a test tube of AgNO3.


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