Question

Dr Kumar is trying to identify an unknown metal Z. When he places it in copper sulphate solution, there is a reaction and red brown pieces of copper fall to the bottom the test tube. When he placed it in magnesium sulphate solution, nothing happens. Which one of the elements given below do you think it is?
(a) sodium
(b) iron
(c) calcium
(d) barium

Answer 1

(b) iron

The unknown metal Z should be iron. Among the given choices, only iron is less reactive than magnesium. Thus, iron, (placed above copper in the reactivity series) being more reactive than copper, displaces copper from the copper sulphate solution. But, iron, (placed below magnesium in the reactivity series) being less reactive than magnesium, cannot displace magnesium from its magnesium sulphate solution.