Question

give reason why copper is used to make hot water tanks and not steel (an alloy of iron)

Answer 1

Copper is used to make hot water tanks and not steel because iron is more reactive than copper and it also reacts with hot steam to produce ferrousoferric oxide, and due to this the body of tank will become weak. Therefore copper is used because it does not react with hot water and will not make the tank weak.

Answer 2

Copper is used to make hot water tank because it doesn't react with hot water or steam but steel (an alloy of iron) reacts with steam. The reaction is given below:
3Fe+4H2O----->Fe3O4+4H2
Hope it helps:))