What is the volume of $0.1 \, N \, HCl$ required to react completely with $1.0 \, g$ of pure calcium carbonate? (in $cm^3$)

$A$ 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 $M$)

$A$ mixture of gases contains $H_2$ and $O_2$ gases in the ratio of $1 : 4$ $(w/w)$. What is the molar ratio of the two gases in the mixture?

$25 \ cm^3$ of oxalic acid completely neutralized $0.064 \ g$ of sodium hydroxide. The molarity of the oxalic acid solution is: (in $M$)

$19 \ g$ of a mixture containing $NaHCO_3$ and $Na_2CO_3$ on complete heating liberated $1.12 \ L$ of $CO_2$ at $STP$. The weight of the remaining solid was $15.9 \ g$. What is the weight (in $g$) of $Na_2CO_3$ in the mixture before heating?

How many grams of concentrated nitric acid solution should be used to prepare $250 \ mL$ of $2.0 \ M \ HNO_3$? The concentrated acid is $70\% \ HNO_3$ by mass.