Which one of the following compounds in aqueous solution gives a white precipitate with perchloric acid?

Which of the following statements is false for alkali metals?

Hydrogen is not obtained when zinc reacts with

The atomic radii of alkali metals $(M)$ lie in the order $Li < Na < K < Rb$,but the radii of $M^{+}$ ions in aqueous solution lie in the reverse order $Li^{+} > Na^{+} > K^{+} > Rb^{+}$. What is the reason for this reverse order (on going from $Li$ to $Rb$)?

Which of the properties of alkali metals is not listed correctly?

Sodium reacts more vigorously with water than lithium because...