What is the nature of the $P$ versus $1/V$ graph at a constant temperature?

An ideal gas initially at pressure $1 \, bar$ is being compressed from $30 \, m^{3}$ to $10 \, m^{3}$ volume and its temperature decreases from $320 \, K$ to $280 \, K$. Find the final pressure of the gas (in $bar$).

$S.I.$ unit of universal gas constant is

$A$ container of fixed volume contains a gas at $27^{\circ} C$. To double the pressure of the gas,the temperature of the gas should be raised to . . . . . . ${ }^{\circ} {C}$.

An open glass tube is immersed in mercury such that a length of $8 \ cm$ extends above the mercury level. The open end of the tube is then closed and sealed,and the tube is raised vertically by an additional $46 \ cm$. What will be the length of the air column above the mercury in the tube now? (Atmospheric pressure = $76 \ cm$ of $Hg$)

The volume of a gas at pressure $21 \times 10^4 \ N/m^2$ and temperature $27^\circ C$ is $83 \ L$. If $R = 8.3 \ J/mol/K$,then the quantity of gas in $gm-mole$ will be: