In the dark,which of the following reacts with hydrogen?

Describe the physical and chemical properties of the elements of group $17$.

Phosphorus reacts with $SO_2Cl_2$ to form $PCl_5$ and $X$. At $723 \ K$,$HCl$ gas reacts with $O_2$ in the presence of $CuCl_2$ to form water and $Y$. $Y$ reacts with $X$ in water to form two acids $A$ and $B$. What are $A$ and $B$ respectively?

Which of the following elements belongs to group $17$ of the periodic table?

Arrange the following in the order of property indicated for each set:
$(i)$ $F_{2}, Cl_{2}, Br_{2}, I_{2}$ - increasing bond dissociation enthalpy.
$(ii)$ $HF, HCl, HBr, HI$ - increasing acid strength.
$(iii)$ $NH_{3}, PH_{3}, AsH_{3}, SbH_{3}, BiH_{3}$ - increasing base strength.

Identify the correct pairs in which the chemical substance given is correctly matched with its use.

Chemical substance	Use
$A. Cl_2$	Preparation of phosgene
$B. I_2O_5$	Estimation of $CO$
$C. O_3$	Disinfectant