How many kilograms of $CaCO_3$ must be heated to obtain $56$ kilograms of $CaO$? [Atomic masses: $Ca = 40, C = 12, O = 16$]

$24 \ g$ of $Mg$ metal reacts with water. How many moles of $H_2$ will be liberated? ............. $mol$

What is the volume occupied by $0.5 \ mol$ of $CO_2$ at $STP$ (in $dm^3$)?

The concentrated sulphuric acid that is peddled commercially is $95\%\, H_2SO_4$ by weight. If the density of this commercial acid is $1.834\, g\, cm^{-3},$ the molarity of this solution is ........... $M$.

The volume of $0.1 \ M$ oxalic acid that can be completely oxidized by $20 \ mL$ of $0.025 \ M$ $KMnO_4$ solution is (in $mL$)

If $1.5 \, mol$ of oxygen reacts with $Al$ to form $Al_2O_3$,calculate the mass of aluminum used in the reaction in grams.