$A$ flask is weighed when filled with methane $(CH_4)$. The methane is then removed,and the flask is weighed again. When the flask is filled with oxygen $(O_2)$ at the same temperature and pressure,the mass of oxygen will be:

How many gram-equivalents of $NaOH$ are required to neutralize $25 \ cm^{3}$ of a decinormal $HCl$ solution?

How many grams of $60\% \, H_2SO_4$ are required for the complete reaction of $100 \, g \, CaCO_3$?

$A$ cylinder of cooking gas in a household contains $11.6 \, kg$ of butane. The thermochemical reaction for the combustion of butane is,
$2 C_4H_{10(g)} + 13 O_{2(g)} \longrightarrow 8 CO_{2(g)} + 10 H_2O_{(l)}$
$\Delta H = -2658 \, kJ/mol$
If the household needs $15000 \, kJ$ of energy per day,the cooking gas cylinder will last for about $...... \, days$.

Aluminium reduces manganese dioxide to manganese at high temperature. The amount of aluminium required to reduce one $g \ mol$ of manganese dioxide is $.....$

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?