The active mass of benzene $(C_6H_6 = 78)$ with a density of $1.56 \, g/mL$ is .......

The decomposition of $CaCO_3$ produces $11.2 \, dm^3$ of $CO_2$ gas at $STP$. What mass of $KOH$ in grams is required to completely neutralize this gas?

How many grams of $3-$hydroxypropanal $(MW=74)$ must be dehydrated to produce $7.8 \ g$ of acrolein $(MW=56)$ $(C_3H_4O)$ if the percentage yield is $64\%$? (Round off to the nearest integer).
[Given: Atomic masses: $C = 12.0 \ u, H = 1.0 \ u, O = 16.0 \ u$]

What is the weight in $g$ of potassium chlorate $(KClO_3)$ required to produce the oxygen needed for the complete combustion of $84 \ L$ of $CO$ at $N.T.P$?

Mass of magnesium required to produce $220 \ mL$ of hydrogen gas at $STP$ on reaction with excess of dil. $HCl$ is (Given: Molar mass of $Mg$ is $24 \ g \ mol^{-1}$)

If $6.022 \times 10^{20}$ atoms are present in $100 \ mL$ of urea solution,then find out the molarity of the urea solution. (in $M$)