Which among the following is the strongest acid?

Chlorine on reaction with hot and concentrated sodium hydroxide gives

Select the correct set of species which cannot react with water but react with $NaOH$:
$(i) \, NO_2$ $(ii) \, P_4$ $(iii) \, Al$ $(iv) \, I_2$

Which of the following represents the correct order of oxidising power of halogens in water?

Which halogen is known to cause the reaction given below:
$2 Cu^{2+} + 4 X^{-} \rightarrow Cu_2 X_{2(s)} + X_2$

Which among the following compounds is $NOT$ a colourless gas?