$3 \ L$ mixture of $C_2H_6$ and $C_3H_8$ produces $8 \ L$ of $CO_2$ upon complete combustion. Find the volume of $C_2H_6$ in the mixture.

$24 \ g$ of $Mg$ metal reacts with water. How many moles of $H_2$ will be liberated? ............. $mol$

What is the percentage atom economy during the conversion of reactant to product if the formula weight of reactants is $246 \ u$ and that of the product is $123 \ u$ (in $\%$)?

The molarity of a $98\%$ by weight solution of $H_2SO_4$ is .......... $M$. The density of the solution at $35^o C$ is $1.84 \ g/cm^3$.

$A$ sample of $NaOH$ weighing $0.38 \ g$ is dissolved in water to make $50.0 \ mL$ of solution in a volumetric flask. What is the molarity of the resulting solution in $M$?

How many $g$ of $KOH$ are required to completely neutralize $12.6 \, g$ of $HNO_3$?