Which quantity is constant for two gases of equal volume at the same pressure and temperature?

The graph shows the $PV$ vs $P$ plot for different gases at a constant temperature. Which graph represents an ideal gas?

What is the ratio of the universal gas constant $(R)$ to the Avogadro number $(N_A)$?

$A$ tyre kept outside in sunlight bursts after some time because of:

At absolute zero temperature,the pressure of an ideal gas will be

$A$ thin tube sealed at both ends is $100 \ cm$ long. It lies horizontally, the middle $20 \ cm$ containing mercury and two equal ends containing air at standard atmospheric pressure. If the tube is now turned to a vertical position, by what amount will the mercury be displaced? (Given: cross-section of the tube can be assumed to be uniform) ........ $cm$