$A$ solution of sulfuric acid contains $80\%$ $H_2SO_4$ by weight and has a specific gravity of $1.71$. What is its normality?

In the combustion of $2.0 \ g$ of methane,$25 \ kcal$ of heat is liberated. The heat of combustion of methane would be ..... $kcal$.

Equal masses of methane $(CH_4)$ and oxygen $(O_2)$ are mixed in an empty container at $25\,^oC$. The fraction of the total pressure exerted by oxygen is:

Some $CO_2$ gas was kept in a sealed container at a pressure of $1 \ atm$ and at $273 \ K$. This entire amount of $CO_2$ gas was later passed through an aqueous solution of $Ca(OH)_2$. The excess unreacted $Ca(OH)_2$ was later neutralized with $0.1 \ M$ of $40 \ mL$ $HCl$. If the volume of the sealed container of $CO_2$ was $x$,then $x$ is $............. \ cm^3$ $(nearest \ integer)$.
$[$Given : The entire amount of $CO_{2(g)}$ reacted with exactly half the initial amount of $Ca(OH)_2$ present in the aqueous solution.$]$

$NaClO_{3}$ is used,even in spacecrafts,to produce $O_{2}.$ The daily consumption of pure $O_{2}$ by a person is $492 \ L$ at $1 \ atm, 300 \ K.$ How much amount of $NaClO_{3},$ in grams,is required to produce $O_{2}$ for the daily consumption of a person at $1 \ atm, 300 \ K?$
$2NaClO_{3(s)} + Fe_{(s)} \rightarrow 3O_{2(g)} + 2NaCl_{(s)} + FeO_{(s)}$
$R = 0.082 \ L \ atm \ mol^{-1} K^{-1}$

The molecular formula of a commercial resin used for exchanging ions in water softening is $C_8H_7SO_3^- Na^+$ $(Mol. \ wt. 206)$. What would be the maximum uptake of $Ca^{2+}$ ions by the resin when expressed in mole per gram resin?