How many millilitres of $6.0 \ M$ hydrochloric acid should be used to prepare $150 \ mL$ of a solution which is $0.30 \ M$ in hydrogen ion?

At $300 \ K$ and $1 \ atm$,$15 \ mL$ of a gaseous hydrocarbon requires $375 \ mL$ of air containing $20 \% \ O_2$ by volume for complete combustion. After combustion,the gases occupy $330 \ mL$. Assuming that the water formed is in liquid form and the volumes were measured at the same temperature and pressure,the formula of the hydrocarbon is:

The weight of calcium oxide formed by burning $20 \ g$ of calcium in excess oxygen is $.... \ g$

The volume of $0.1 \, M$ aqueous $KOH$ solution required for the complete neutralization of $20 \, mL$ of $0.1 \, M$ aqueous $H_3PO_3$ solution is .......... $mL$.

If $0.45 \ g$ of a gas with molecular weight $60$ and $0.22 \ g$ of another gas with molecular weight $44$ are present,and the total pressure exerted by the mixture is $75 \ cm \ Hg$,then the partial pressure of the second gas is .......... $cm$ of $Hg$.

$A$ $20 \ mL$ solution of $KMnO_4$ with a concentration of $1 \ N$ reacts with $20 \ mL$ of oxalic acid. The weight of oxalic acid in the $1 \ N$ solution is ......... $g$.