Hydrocarbones Temperature Vapor Pressures

Reference data and engineering information about hydrocarbones temperature vapor pressures for chemistry applications.

hydrocarbonestemperaturevaporpressures

Overview

Engineering reference data for Hydrocarbones Temperature Vapor Pressures in chemistry.

Key Formulas

Ideal Gas Law

$PV = nRT$

Pressure × Volume = moles × gas constant × temperature.

Molarity

$M = \frac{n}{V}$

Moles of solute per liter of solution.

pH

$pH = -\log_{10}[H^+]$

Measure of acidity.

Variables

Symbol	Description	Unit
$P$	Pressure	Pa
$V$	Volume	m³
$n$	Moles	mol
$R$	Gas constant	8.314 J/(mol·K)

Vapor Pressure Data for Common Hydrocarbons

The following table provides representative vapor pressure data for propane, n-butane, n-pentane, and n-heptane at various temperatures. This data is crucial for process design involving separation, storage, and pipeline transport of these compounds.

7 rows

Approximate vapor pressure (kPa) vs. temperature for selected hydrocarbons
Temperature(°C)	Propane(kPa)	n-Butane(kPa)	n-Pentane(kPa)	n-Heptane(kPa)
-20	243	47	8	0.6
0	478	103	24	1.6
20	834	208	57	4.8
40	1341	379	116	12.3
60	2039	638	215	27.6
80	2979	1012	374	55.3
100	4238	1536	613	102

Source: engineeringtoolbox.com

Hydrocarbon Physical Properties

Understanding vapor pressure requires context about the compounds' basic properties. The following table summarizes key data for the hydrocarbons discussed.

4 rows

Basic physical properties of the listed hydrocarbons
Compound	Formula	Molecular Weight(g/mol)	Normal Boiling Point(°C)
Propane	C₃H₈	44.1	-42.1
n-Butane	C₄H₁₀	58.12	-0.5
n-Pentane	C₅H₁₂	72.15	36.1
n-Heptane	C₇H₁₆	100.21	98.4

Source: CRC Handbook of Chemistry and Physics

Key Relationships and Equations

The vapor pressure of a pure component is a strong function of temperature. This relationship is quantitatively described by the Clausius-Clapeyron equation, which can be integrated to yield:

$\ln\left(\frac{P_2}{P_1}\right) = \frac{\Delta H_{vap}}{R} \left(\frac{1}{T_1} - \frac{1}{T_2}\right)$

Where:

$P_1, P_2$ are vapor pressures at temperatures $T_1, T_2$ (in Kelvin).
$\Delta H_{vap}$ is the enthalpy of vaporization (J/mol).
$R$ is the universal gas constant (8.314 J/mol·K).

For engineering calculations over wider temperature ranges, the Antoine equation is more commonly used due to its empirical accuracy:

$\log_{10}(P) = A - \frac{B}{C + T}$

Where $P$ is in mmHg, $T$ is in °C, and $A, B, C$ are substance-specific constants.

Interactive Charts

Vapor pressure versus temperature - hydrocarbones propane butane pentane heptane

Fuels and Chemicals - Autoignition Temperatures

References

Original Source

Source: engineeringtoolbox.com