Enter the pressure (Pa), the molecular weight (kg/mol), and the temperature (K) into the Density From Molecular Weight Calculator. The calculator will evaluate and display the Density From Molecular Weight.
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Density From Molecular Weight Formula
The following formula is used to calculate the Density From Molecular Weight.
D = P * MW / (R*T)
- Where D is the Density From Molecular Weight (kg/m^3)
- P is the pressure (Pa)
- MW is the molecular weight (kg/mol)
- T is the temperature (K)
- R is the Universal Gas Constant (8.314)
To calculate density from molecular weight, multiply the pressure by the molecular weight, then divide by the product of the temperature and gas constant.
| Molecular Weight (g/mol) | Density (kg/m³) |
|---|---|
| 2 | 0.082 |
| 4 | 0.164 |
| 16 | 0.654 |
| 17 | 0.695 |
| 18 | 0.736 |
| 20 | 0.818 |
| 28 | 1.145 |
| 28.97 | 1.184 |
| 30 | 1.226 |
| 32 | 1.308 |
| 34 | 1.390 |
| 36.46 | 1.490 |
| 40 | 1.635 |
| 44 | 1.799 |
| 58 | 2.371 |
| 64 | 2.616 |
| 84 | 3.434 |
| 98 | 4.006 |
| 131.29 | 5.367 |
| 146.06 | 5.970 |
| * Rounded to 3 decimals. Ideal gas relation: ρ = (P × M) / (R × T). Assumes P = 1 atm (101,325 Pa), T = 25°C (298.15 K), R = 8.314 J/(mol·K). 1 g/mol → 0.040877 kg/m³ at these conditions. | |
How to Calculate Density From Molecular Weight?
The following example problems outline how to calculate Density From Molecular Weight.
Example Problem #1
- First, determine the pressure (Pa).
- The pressure (Pa) is given as 3000.
- Next, determine the molecular weight (kg/mol).
- The molecular weight (kg/mol) is calculated as: .44.
- Next, determine the temperature (K).
- The temperature (K) is found to be: 250.
- Finally, calculate the Density From Molecular Weight using the formula above:
D = P * MW / (R*T)
Inserting the values from above yields:
D = 3000 * .44 / (8.314*250) = .635 (kg/m^3)
Example Problem #2
The variables needed for this problem are provided below:
pressure (Pa) = 240
molecular weight (kg/mol) = 205
temperature (K) = 100
This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer.
D = P * MW / (R*T) = (kg/m^3)
