Which catalyst is used in the industrial manufacture of hydrogen gas?

When a metal $X$ is treated with cold water,it gives a basic salt $Y$ with molecular formula $XOH$ (Molecular mass $= 40$) and liberates a gas $Z$ which easily catches fire. Identify $X, Y, Z$.

Which of the following metals is the lightest?

Which metal does not react with cold or hot water,but reacts with steam to produce $H_2$ gas?

Which process occurs at the anode during the process of electrolysis?

When a copper wire is left in silver nitrate solution,it is observed that the solution turns bluish green.
$(a)$ Explain the observation.
$(b)$ Write the balanced chemical equation to represent the change taking place.