What happens when calcium is treated with water?

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 $X$, $Y$, and $Z$, and write the chemical reaction involved.

Which ore is concentrated by the froth flotation process?

Which of the following statements is incorrect?

Define an alloy. How is an alloy prepared?

Write the chemical equations for the reactions of zinc granules with:
$(i)$ Sulphuric acid
$(ii)$ Hydrochloric acid
$(iii)$ Aluminium chloride
$(iv)$ Sodium hydroxide
$(v)$ Nitric acid