Chlorine gas is treated with aqueous sodium hydroxide. The oxidation number of chlorine changes from $0$ to $-1$ and also from $0$ to $+1$. At what conditions does this reaction take place, and what is the colour of the solid silver salt containing chlorine in oxidation state $-1$?
- Acold, dilute alkali / white
- Bcold, dilute alkali / yellow
- Chot, concentrated alkali / white
- Dhot, concentrated alkali / yellow