How many moles of $H_2O$ are liberated when one mole of hydrated $MgCl_2$ is heated?

Heating oxygen in the presence of a catalyst results in $15\%$ conversion to ozone. How many grams of oxygen are required to produce $33.6 \ L$ of $O_3$ at $STP$?

The density of $2 \ M$ aqueous solution of $NaOH$ is $1.28 \ g \ cm^{-3}.$ The molality of the solution is $... \ m$ [Given that molecular mass of $NaOH = 40 \ g \ mol^{-1}$]

Molarity of $0.2 \ N \ H_2SO_4$ is

What is the value of percent atom economy when an organic compound of formula weight $75 \ u$ is obtained from reactants having sum formula weight $225 \ u$?

What will be the volume of $CO_2$ at $S.T.P.$ obtained by heating $9.85 \ g$ of $BaCO_3$? (Atomic mass of $Ba = 137$)