Question

An iron nail is added to each of the two test tubes ‘P’ and ‘Q’ containing aqueous copper (II) sulphate, and aqueous silver nitrate respectively. Which of the following observation is correct?

विकल्प

• In test tube ‘P’ iron nail is coated with a blue coating and in test tube ‘Q’ there is no reaction.

• Iron nail is coated with a brown coating in test tube ‘P’ and silver coating in test tube ‘Q’.

• There is no reaction in either of the test tubes ‘P’ or ‘Q’.

• There is no reaction in test tube ‘P’ but a silver coating on iron nail is seen in test tube ‘Q’.

Answer 1

Iron nail is coated with a brown coating in test tube ‘P’ and silver coating in test tube ‘Q’.

Explanation:

Fe displaces Cu from CuSO₄, resulting in dark Cu, and it also displaces Ag from AgNO₃, leaving a silver coating on the nail. Don’t assume that silver is too unreactive to be displaced by iron, which leads to an incorrect reaction, because iron does displace silver from AgNO₃, resulting in a silver coating.