What volume of dioxygen is required for complete combustion of $2 \, \text{volumes}$ of acetylene gas at $NTP$?

Concentrated sulfuric acid is $95\%$ by weight and its density is $1.8 \ g \ cm^{-3}$. What volume of concentrated acid in $cm^3$ is required to prepare $4 \ L$ of $0.4 \ M \ H_2SO_4$ solution (in $.7$)?

When $26 \ mL$ of $CO_2$ is passed over hot coke,the volume of $CO$ produced is .......... $mL$.

$10 \ g$ of a piece of marble $(CaCO_3)$ was put into excess of dilute $HCl$ acid. When the reaction was complete,$1120 \ mL$ of $CO_2$ was obtained at $STP$. The percentage of pure $CaCO_3$ in the marble is $............ \%$.

Hardness of water is $200 \ ppm$. Calculate the molarity and normality of $CaCO_3$ in the water.

What is the weight of oxygen required for the complete combustion of $2.8 \, kg$ of ethylene? (in $kg$)