Assign $A, B, C, D$ from the given type of reaction.
$KI + BiI_3 \downarrow \longrightarrow K[BiI_4]$

The unbalanced chemical reactions given in List-$I$ show missing reagent or condition $(?)$ which are provided in List-$II$. Match List-$I$ with List-$II$ and select the correct answer using the code given below the lists:

List-$I$	List-$II$
$P. \ PbO_2 + H_2SO_4 \xrightarrow{?} PbSO_4 + O_2 + \text{other product}$	$1. \ NO$
$Q. \ Na_2S_2O_3 + H_2O \xrightarrow{?} NaHSO_4 + \text{other product}$	$2. \ I_2$
$R. \ N_2H_4 \xrightarrow{?} N_2 + \text{other product}$	$3. \ \text{Warm}$
$S. \ XeF_2 \xrightarrow{?} Xe + \text{other product}$	$4. \ Cl_2$

Codes: $P \quad Q \quad R \quad S$

$CO_2$ and $SO_2$ gases can be distinguished by using:

By passing $H_2S$ gas in acidified $KMnO_4$ solution,we get

$20 \ mL$ of $Fe^{2+}$ solution of certain concentration has completely reacted with $20 \ mL$ of $0.01 \ M \ K_2Cr_2O_7$ in acidic medium. If $20 \ mL$ of same $Fe^{2+}$ solution has reacted completely with $20 \ mL$ of $KMnO_4$ solution in acidic medium,the molarity of $KMnO_4$ solution is: (in $M$)

Assign $A, B, C, D$ from the given type of reaction.
$AgNO_3 \,(Solution) + NaF \,(Solution) \longrightarrow$ No reaction