Mass of methane required to produce $22 \ g$ of $CO_2$ after complete combustion is . . . . . . $g.$ (Given Molar mass in $g \ mol^{-1}$: $C=12.0, H=1.0, O=16.0$)

For the combustion reaction $C_2H_{6(g)} + nO_{2(g)} \to CO_{2(g)} + H_2O_{(l)}$,what is the ratio of the stoichiometric coefficients of $CO_2$ and $H_2O$ in the balanced equation?

The right option for the mass of $CO_2$ produced by heating $20 \ g$ of $20 \%$ pure limestone is $........ \ g$ (Atomic mass of $Ca = 40$) $[CaCO_3 \stackrel{1200 \ K}{\longrightarrow} CaO + CO_2]$

$0.43 \ g$ of a metal of valence $2$ was dissolved in $50 \ mL$ of $0.5 \ M \ H_2SO_4$ solution. The unreacted acid required $14.2 \ mL$ of $1 \ M \ NaOH$ solution for neutralization. The atomic weight of the metal is: (in $u$)

The hardness of a water sample (in terms of equivalents of $CaCO_3$) containing $10^{-3} \ M \ CaSO_4$ is ................... $ppm$ (Molecular mass of $CaSO_4 = 136 \ g \ mol^{-1}$)

In the preceding question,the amount of $Na_2CO_3$ present in the solution is ............. $g$.