$0.7 \ g$ of $Na_2CO_3 \cdot xH_2O$ were dissolved in water and the volume was made to $100 \ mL$. $20 \ mL$ of this solution required $19.8 \ mL$ of $N/10 \ HCl$ for complete neutralization. The value of $x$ is:

$2.5 \ cm^{3}$ of $0.2 \ M \ H_{2}SO_{4}$ solution is diluted to $0.5 \ dm^{3}$. Find the normality of the diluted solution. (in $N$)

In the complete combustion of $C_4H_{10}$,the number of moles of oxygen required is:

$20.0 \ g$ of a magnesium carbonate sample decomposes on heating to give carbon dioxide and $6.0 \ g$ magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight of $Mg = 24$)

$A$ metal chloride contains $55.0 \%$ of chlorine by weight. $100 \ mL$ of vapours of the metal chloride at $STP$ weigh $0.57 \ g$. The molecular formula of the metal chloride is $...$. (Given: Atomic mass of chlorine is $35.5 \ u$)

Equal weights of ethane and hydrogen are mixed in an empty container at $25^{\circ} C$. The fraction of total pressure exerted by hydrogen is