What is the weight of $CH_4$ gas in a $9 \ L$ cylinder at $27 \ ^oC$ temperature and $1 \ atm$ pressure in $g$?

An ideal gas $(X)$ present in a vessel of volume $V \ L$ exerted a pressure of $16.4 \ atm$ at $200 \ K$. What is its concentration in $mol \ L^{-1}$? (Given $R=0.082 \ L \ atm \ mol^{-1} \ K^{-1}$)

Calculate the number of total atoms and molecules in $4 \, L$ of $SO_2$ gas at $350 \, K$ temperature and $10^3 \, Pa$ pressure. $[R = 8.3144 \, J \, K^{-1} \, mol^{-1}]$.

The correct combined gas law equation is:

$A$ vessel contains $1.6 \ g$ of dioxygen at $STP$ ($273.15 \ K$,$1 \ atm$ pressure). The gas is now transferred to another vessel at constant temperature,where pressure becomes half of the original pressure. Calculate
$(A)$ volume of the new vessel.
$(B)$ number of molecules of dioxygen.

If a gas occupies $1 \, L$ volume at atmospheric pressure,what will be the volume of the same amount of gas at $750 \, mm \, Hg$ pressure at the same temperature?