Partial Pressure Ideal Gas Law Total Mixture Blending

Reference data and engineering information about partial pressure ideal gas law total mixture blending for gases and compressed air applications.

partialpressureidealgas

Overview

Engineering reference data for Partial Pressure Ideal Gas Law Total Mixture Blending in gases and compressed air.

$PV = nRT$

Pressure × Volume = moles × gas constant × temperature.

$P_1 V_1 = P_2 V_2$

At constant temperature.

$\frac{V_1}{T_1} = \frac{V_2}{T_2}$

At constant pressure.

Consider 100 g of dry air in a 50 L container at 120°C (393.15 K). The weight fractions of the primary components are:

Using the molar mass (M) of each gas:

n_i = \frac{\text{mass}_i}{M_i} = \frac{m_{\text{total}} \times \text{wt fraction}_i}{M_i}

Total moles: $n_{\text{tot}} = 2.693 + 0.725 + 0.032 + 0.001 = 3.451 \text{ mol}$

Using $R = 0.08206 \text{ L·atm/(mol·K)}$ , $T = 393.15 \text{ K}$ , $V = 50 \text{ L}$ :

P_{\text{tot}} = \frac{n_{\text{tot}} R T}{V} = \frac{3.451 \times 0.08206 \times 393.15}{50} = 2.226 \text{ atm}

Mole fraction $X_i = n_i / n_{\text{tot}}$ and partial pressure $P_i = X_i \times P_{\text{tot}}$ .

5 rows

Calculated composition and partial pressures for 100 g of dry air at 120°C in a 50 L container.
Gas	Moles (nᵢ)(mol)	Mole Fraction (Xᵢ)	Partial Pressure (Pᵢ)(atm)
N₂	2.693	0.7805	1.737
O₂	0.725	0.2101	0.468
Ar	0.032	0.0093	0.021
CO₂	0.001	0.00029	0.0006
Total	3.451	1	2.226

Source: Derived from provided example.

Dalton's Law of Partial Pressures:
$P_{\text{tot}} = \sum_{i=1}^{k} P_i = P_1 + P_2 + \dots + P_k$
where $k$ is the number of component gases.
Partial Pressure from Moles (Ideal Gas):
$P_i = \frac{n_i R T}{V}$
Total Pressure from Total Moles (Ideal Gas):
$P_{\text{tot}} = \frac{n_{\text{tot}} R T}{V}$
Mole Fraction ( $X_i$ ):
$X_i = \frac{n_i}{n_{\text{tot}}}$
Partial Pressure from Mole Fraction:
$P_i = X_i \cdot P_{\text{tot}}$