The heat of combustion of ethylene $C_2H_{4(g)}$ is $-1420 \, kJ/mol$. The number of litres of $C_2H_4$ at $NTP$ that would evolve $355 \, kJ$ on combustion is:

$A$ $10 \ g$ effervescent tablet containing sodium bicarbonate $(NaHCO_3)$ and oxalic acid $(H_2C_2O_4)$ releases $0.25 \ L$ of $CO_2$ at $T = 298.15 \ K$ and $p = 1 \ bar$. If the molar volume of $CO_2$ is $25.0 \ L \ mol^{-1}$ under these conditions,what is the percentage by mass of sodium bicarbonate in each tablet? [Molar mass of $NaHCO_3 = 84 \ g \ mol^{-1}$,Molar mass of $H_2C_2O_4 = 90 \ g \ mol^{-1}$]

$CaCO_3$ reacts with $HCl$ to produce $CaCl_2, CO_2$ and $H_2O$. The approximate mass (in $g$) of $CaCO_3$ required to react completely with $25 \ mL$ of $0.75 \ M \ HCl$ is (atomic mass of $Ca=40, C=12, O=16, Cl=35.5$ and $H=1$).

$18 \ L$ mixture of $N_2$ and $H_2$ gives maximum $6 \ L$ of $NH_3$ at same temperature and pressure. What will be the ratio of $N_2$ and $H_2$ initially taken?

What is the weight in $g$ of potassium chlorate $(KClO_3)$ required to produce the oxygen needed for the complete combustion of $84 \ L$ of $CO$ at $N.T.P$?

$0.43 \ g$ of a metal of valence $2$ was dissolved in $50 \ mL$ of $0.5 \ M \ H_2SO_4$ solution. The unreacted acid required $14.2 \ mL$ of $1 \ M \ NaOH$ solution for neutralization. The atomic weight of the metal is: (in $u$)