Molarity of a given orthophosphoric acid solution is $3 \ M$. Its normality is (in $N$)

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.$]$

$A$ $40 \%$ $HCl$ solution has density $1.2 \ g \ mL^{-1}$. The molarity of the solution is nearly . . . . . . (in $M$)

$A$ sample of nitric acid has a density of $1.41 \ g \ mL^{-1}$ and the mass percentage of nitric acid is $69 \%$. Calculate the concentration of nitric acid in the sample in moles per liter. (in $M$)

$0.1 \text{ mole}$ of potassium permanganate was heated at $300^{\circ}C$. What is the weight (in $g$) of the residue? ($Mn = 55 \text{ u}$,$K = 39 \text{ u}$,$O = 16 \text{ u}$)

The combustion of methane is represented by the following equation: $CH_4(g) + 2O_2(g) \rightarrow CO_2(g) + 2H_2O(l); \Delta H = -890 \, kJ \, mol^{-1}$. How many grams of carbon dioxide are produced when $445 \, kJ$ of heat is released?