While combusting in air, $4 \ g$ of $H_2$ gas was completely converted into water. If $36 \ \mu mole$ of $CO_2$ from air is dissolved into that water, what is the concentration of $CO_2$?

$x \ g$ of methane was burnt completely in the presence of oxygen. The liberated gases were passed into a solution containing $370 \ g$ of $Ca(OH)_2$. The weight of white precipitate obtained was $500 \ g$. What is the value of $x$ (in $g$)? (Given: $C=12, H=1, Ca=40, O=16 \ u$)

What is the weight of $50\%$ pure $HCl$ required to react completely with $100 \ g$ of $100\%$ pure limestone $(CaCO_3)$ (in $g$)?

$A$ 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:

In the reaction $SO_{2(g)} + 1/2 O_{2(g)} \to SO_{3(g)}$,how many liters of air at $STP$ are required for the complete conversion of $6.4 \, g$ of $SO_2$ to $SO_3$ (in $, L$)? (Assume air contains $20 \% \, O_2$ by volume).

Which of the following is the correct formula to determine percent atom economy?