What is the total number of particles present in base centred unit cell?

Which of the following equation relates temperature of a reaction with $\Delta \mathrm{H}^{\circ}$ and $\Delta \mathrm{S}^{\circ}$ at equilibrium?

Calculate the molality of solution if its depression in freezing point is 0.18 K . $\left[\mathrm{K}_{\mathrm{f}}=1.6 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right]$

For the reaction,

$$\mathrm{H}_{2(g)}+\mathrm{Br}_{2(8)} \longrightarrow 2 \mathrm{HBr}_{(\mathrm{g})}, \mathrm{r}=\mathrm{k}\left[\mathrm{H}_2\right]\left[\mathrm{Br}_2\right]^{\frac{1}{2}}$$

What is the molecularity and order of reaction respectively?