Ideal gas law (pV = nRT)

The ideal gas law (Clapeyron equation) relates pressure, volume, amount of substance and temperature:

$pV=nRT$

where $R=8.314\ \tfrac{\text{J}}{\text{mol·K}}$. Enter three of the four quantities ($p$ in Pa, $V$ in m³, $n$ in moles, $T$ in kelvin) and the calculator finds the missing one.

The second mode solves a gas process for a fixed amount of gas:

$\frac{p_1V_1}{T_1}=\frac{p_2V_2}{T_2}$

From it come the special processes: isothermal ($T$ = const → $p_1V_1=p_2V_2$), isobaric ($p$ = const) and isochoric ($V$ = const). Remember: temperature is always in kelvin.