$PV = nRT$
$PV = k$2) is Boyle's law, it is the only inverse relationship of the ideal gas law. $\frac{V}{T} = k$ is Charles's law, it is a direct relationship. $\frac{V}{n} = k$ is Avogadro's law, it is also a direct relation. $\frac{P}{T} = k$ is Gay-Lussac's law, it is once again a direct relationship.
1 mole of any gas at STP condition will have a volume equal to 22.4 L. Standard conditions are represented by the following:
It isn't necessarily required to know these ones as the ideal gas law covers them.
$\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$
This can be simplified to (depending on if certain variables are equal on both sides)
$\frac{V_1}{n_1} = \frac{V_2}{n_2}$
“Molar Mass kitty cat”
all good cats put $dRT$ over their $P$
$M = \frac{dRT}{P}$ where $M$ is the molar mass, $d$ is the density, and $R$, $T$, and $P$ represent values from the ideal gas law.