The product of the pressure and volume of an ideal gas is

$A$ gas is enclosed in a vessel at a constant temperature at a pressure of $5 \text{ atm}$ and volume $4 \text{ L}$. Due to a leakage in the vessel,after some time,the pressure is reduced to $4 \text{ atm}$. As a result,the:

An ideal gas has an initial pressure of $3$ pressure units and an initial volume of $4$ volume units. The table gives the final pressure and volume of the gas (in those same units) in four processes. Which processes start and end on the same isotherm?

$A$. Process $A$	$P=5, V=7$
$B$. Process $B$	$P=4, V=6$
$C$. Process $C$	$P=12, V=1$
$D$. Process $D$	$P=6, V=3$

Pressure of a gas of constant volume at $20^{\circ} C$ is $90 \ cm$ of $Hg$. At what temperature the pressure would change to $75 \ cm$ of $Hg$ (in $^{\circ} C$)?

What is the number of oxygen molecules in a cylinder of volume $1 \ m^3$ at $27^{\circ}C$ and $13.8 \ Pa$? (Boltzmann constant $k = 1.38 \times 10^{-23} \ JK^{-1}$)

When air is pumped into a cycle tyre, the volume and pressure of the air in the tyre both increase. What about Boyle's law in this case?