Calculate the number of $\mathrm{Ca}^{2+}$ ion in 222 g anhydrous calcium chloride? (At. Mass $\mathrm{Ca}=40, \mathrm{Cl}=35.5$ )

For a reaction, $\mathrm{A} \longrightarrow \mathrm{B}$, rate equation is $\mathrm{r}=\mathrm{k}[\mathrm{A}]^{\circ}$. If initial concentration of reactant is 'a'mol dm ${ }^{-3}$ find half life time of reaction.

Which of the following compounds is formed as major product in the following reaction.

2-Methylbut-2-ene $\xrightarrow[\text { Peroxide }]{\mathrm{HBr}}$ Product

Which from following cations forms least stable complex with same ligand?