At what temperature in the Celsius scale,$V$ (volume) of a certain mass of gas at $27\,^oC$ will be doubled keeping the pressure constant?

Find the moles of $O_2$ having pressure $250 \ bar$ in $500 \ mL$ vessel at $300 \ K$ temperature. $[R = 8.314 \times 10^{-2} \ bar \ L \ K^{-1} \ mol^{-1}]$

$4 \ g$ of an ideal gas $A$ (molar mass $= M_A$) present in a vessel of a volume $V \ L$ exerted a pressure of $5 \ atm$ at $300 \ K$. When $16 \ g$ of another ideal gas $B$ (molar mass $= M_B$) was introduced into this vessel at the same temperature,the pressure increased to $10 \ atm$. What is the correct relationship between $M_A$ and $M_B$?

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

If the density ratio of a gas is $1:2$ and the temperature ratio is $2:1$,what will be the ratio of their pressures?

If the density of neon gas at $350 \ K$ is $0.9 \ g \ L^{-1}$,calculate the pressure of the gas. (in $bar$)