Of the three metals X, Y and Z. X reacts with cold water, Y with hot water and Z with steam only. Identify X, Y and Z and also arrange them in order of increasing reactivity.

Soln:

X reacts with cold water.

Hence , the element should be Sodium Ca + H₂O Ca(OH)₂ + H₂

Y reacts with hotwater, Hence, it is "Magnesium" Mg + H₂O Mg(OH)₂ + H₂

Z reacts with steam only. Hence , it is Iron Fe + H₂O Fe₂O₃+ H₂

Arranging in ascending order (increasing order of reactivity) Fe < Mg < Ca