$0.63 \ g$ of oxalic acid is dissolved to obtain $250 \ cm^3$ of its solution. Find the normality of this solution. [Oxalic acid: $(COOH)_2 \cdot 2H_2O$] (in $N$)

How many grams of $HCl$ will be present in $150 \ mL$ of its $0.52 \ M$ solution?

Some $CO_2$ gas was kept in a sealed container at a pressure of $1 \ atm$ and at $273 \ K$. This entire amount of $CO_2$ gas was later passed through an aqueous solution of $Ca(OH)_2$. The excess unreacted $Ca(OH)_2$ was later neutralized with $0.1 \ M$ of $40 \ mL$ $HCl$. If the volume of the sealed container of $CO_2$ was $x$,then $x$ is $............. \ cm^3$ $(nearest \ integer)$.
$[$Given : The entire amount of $CO_{2(g)}$ reacted with exactly half the initial amount of $Ca(OH)_2$ present in the aqueous solution.$]$

Sulfur trioxide is prepared by the following reactions:
$S_{8(s)} + 8O_{2(g)} \to 8SO_{2(g)}$
$2SO_{2(g)} + O_{2(g)} \to 2SO_{3(g)}$
How many grams of $SO_3$ are obtained from $1 \ mol$ of $S_8$?

In the petroleum industry,a process is carried out to increase the octane number of fuel as follows: $C_7H_{14} \rightarrow C_7H_8 + 3H_2$. In this process,two hydrocarbons are in liquid state while $H_2$ is in gaseous state. What is the percentage decrease in the weight of the liquid in the above reaction?

What is the percentage atom economy when the formula weight of the desired product is $65 \text{ u}$ and the sum of the formula weights of all reactants is $130 \text{ u}$ (in $\%$)?