Four half reactions I to IV are shown below:

I. $$2 \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}_2+2 \mathrm{e}^{-}$$

II. $$4 \mathrm{OH}^{-} \rightarrow \mathrm{O}_2+2 \mathrm{H}_2 \mathrm{O}+2 \mathrm{e}^{-}$$

III. $$\mathrm{Na}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Na}$$

IV. $$2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_2$$

Which two of these reactions are most likely to occur when concentrated brine is electrolysed?

Which property of transition metals enables them to behave as catalysts?

In the two tetrahedral structures of dichromate ion

1 mole of liquid A and 2 moles of liquid $$B$$ make a solution having a total vapour pressure 40 torr. The vapour pressure of pure $$A$$ and pure $$B$$ are 45 torr and 30 torr respectively. The above solution