Ferric alum has the composition $(NH_4)_2SO_4 \cdot Fe_2(SO_4)_3 \cdot xH_2O$,where $x$ is..........

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 $2.$

Natural gas is a mixture of methane and ethane. The heat produced by the complete combustion of $10 \, L$ of this mixture at $S.T.P.$ is $476.6 \, kJ$. Given $\Delta H_{comb} (CH_4) = -894 \, kJ \, mol^{-1}$ and $\Delta H_{comb} (C_2H_6) = -1500 \, kJ \, mol^{-1}$,calculate the percentage of methane and ethane in the mixture by volume.

Assume that a human body requires $2500 \, kcal$ of energy each day for metabolic activity and sucrose is the only source of energy,as per the equation $C_{12}H_{22}O_{11(s)} + 12 \, O_{2(g)} \longrightarrow 12 \, CO_{2(g)} + 11 \, H_2O_{(l)};$ $\Delta H = -5.6 \times 10^6 \, J$. (Fill in the blanks) $(a)$ The energy requirement of the human body per day is $.... \, kJ$. $(b)$ The mass of sucrose required to provide this energy is $........ \, g$ and the volume of $CO_2$ (at $STP$) produced is $......... \, litres.$

What volume of $NH_3$ gas at $STP$ would be needed to prepare $100 \ mL$ of $2.5$ molal $(2.5 \ m)$ ammonium hydroxide solution? (Assume the density of the solution is $1 \ g/mL$)

What is the actual volume occupied by water molecules present in $20 \ cm^3$ of water (in $cm^3$)?