How many grams of bromine are required to react with $21 \ g$ of $C_3H_6$? (Atomic mass of $Br = 80$)

The concentration of a $100 \ mL$ solution containing $X \ g$ of $Na_2CO_3$ (molecular weight $= 106$) is $Y \ M$. The values of $X$ and $Y$ are respectively.

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

$A$ pre-weighed vessel is filled with $O_2$ and weighed at $STP$. It is then evacuated and filled with $SO_2$ gas at the same temperature and pressure,and weighed again. The weight of $O_2$ will be:

The volume of $0.02 \, M$ aqueous $HBr$ required to neutralize $10.0 \, mL$ of $0.01 \, M$ aqueous $Ba(OH)_2$ is $....... \, mL$ (Assume complete neutralization).

If the reduction of a sample of $Cu_2O$ yields $1.27 \, g$ of $Cu$,then how many grams of oxygen must be present in it?