Write formulas for the following compounds:
$(1)$ Mercury $(II)$ chloride
$(2)$ Nickel $(II)$ sulphate
$(3)$ Tin $(IV)$ oxide
$(4)$ Thallium $(I)$ sulphate

$20 \ mL$ of $2 \ M$ $NaOH$ solution is added to $400 \ mL$ of $0.5 \ M$ $NaOH$ solution. The final concentration of the solution is $.......... \times 10^{-2} \ M$. $(Nearest \ integer)$.

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. $16 \ g \ CH_{4(g)}$	$I$. Weighs $28 \ g$
$B$. $1 \ g \ H_{2(g)}$	$II$. $60.2 \times 10^{23}$ electrons
$C$. $1 \ mole \ N_{2(g)}$	$III$. Weighs $32 \ g$
$D$. $0.5 \ mol \ SO_{2(g)}$	$IV$. Occupies $11.2 \ L$ volume at $STP$

Choose the correct answer from the options given below:

Dinitrogen and dioxygen react with each other to form different compounds. The experimental data is given below:

Mass of Dinitrogen	Mass of Dioxygen
$(i) \ 14 \ g$	$16 \ g$
$(ii) \ 14 \ g$	$32 \ g$
$(iii) \ 28 \ g$	$32 \ g$
$(iv) \ 28 \ g$	$80 \ g$

$(a)$ Which law of chemical combination is followed by the above experimental data? State the law.
$(b)$ Fill in the blanks in the following conversions:
$(i) \ 1 \ km = \dots \ mm = \dots \ pm$
$(ii) \ 1 \ mg = \dots \ kg = \dots \ ng$
$(iii) \ 1 \ mL = \dots \ L = \dots \ dm^3$

Bleaching powder and bleach solution are produced on a large scale and used in several household products.
The effectiveness of bleach solution is often measured by iodometry.
$1.$ $25 \ mL$ of household bleach solution was mixed with $30 \ mL$ of $0.50 \ M \ KI$ and $10 \ mL$ of $4 \ N$ acetic acid. In the titration of the liberated iodine,$48 \ mL$ of $0.25 \ N \ Na_2S_2O_3$ was used to reach the end point. The molarity of the household bleach solution is
$(A)$ $0.48 \ M$ $(B)$ $0.96 \ M$ $(C)$ $0.24 \ M$ $(D)$ $0.024 \ M$
$2.$ Bleaching powder contains a salt of an oxoacid as one of its components. The anhydride of that oxoacid is
$(A)$ $Cl_2O$ $(B)$ $Cl_2O_7$ $(C)$ $ClO_2$ $(D)$ $Cl_2O_6$
Give the answer for question $1$ and $2.$

Suppose you have to determine the percentage of carbon dioxide in a sample of a gas available in a container. Which is the best absorbing material for the carbon dioxide?