What is the mass of oxygen in $g$ required to produce enough $CO$ for the complete reduction of $1.6 \ kg$ of $Fe_2O_3$ (molar mass $= 160 \ g/mol$)?

When $5 \ L$ of a gas mixture of methane and propane is perfectly combusted at $0 \ ^\circ C$ and $1 \ atm$,$16 \ L$ of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in $kJ$ ($\Delta H_{comb.} (CH_4) = 890 \ kJ \ mol^{-1},$ $\Delta H_{comb.} (C_3H_8) = 2220 \ kJ \ mol^{-1}$) is

$X \ g$ of nitrobenzene on nitration gave $4.2 \ g$ of $m-$dinitrobenzene. $X = ............ \ g$. $(nearest \ integer)$ [Given: molar mass (in $g \ mol^{-1}$) $C: 12, H: 1, O: 16, N: 14$]

How many grams of $CaCO_3$ must be decomposed to produce $20 \ L$ of $CO_2$ at $750 \ torr$ and $27 \ ^\circ C$?

Volume of $0.6\, M\, NaOH$ required to neutralize $30\, cm^{3}$ of $0.4\, M\, HCl$ is ............. $cm^{3}$

The molarity of a $98\%$ by weight solution of $H_2SO_4$ is .......... $M$. The density of the solution at $35^o C$ is $1.84 \ g/cm^3$.