For our profile project it is crucial to know what the density of helium is at different temperatures and so far we have not been able to find that anywhere, except for the density at 0 and 20 degrees Celsius.
Answer
Hi Jeffrey,
The density of a gas can be easily calculated using the ideal gas law:
P*V = n*R*T
After all, the density is the mass divided by the volume, and the mass of n mol He is equal to:
m = n * M
with M the molar mass of He, 4.0026
The density ρ (Rho) is then:
ρ = m/V
or:
ρ = n*M/V = (p*V/R*T)*M/V = p*M/R*T
We assume that the pressure is 1 atm (of course you can also calculate the density at other pressures) R, the gas constant has the value 0.082056 L.atm/K.mol ; M is the molar mass is 4.0026 g/mole; and T is the temperature in Kelvin, this is equal to the temperature in Celsius + 273.15
If we plug everything into the formula, we get:
| T /°C | ρ/(g/L) |
| 0 | 0.1786 |
| 5 | 0.1754 |
| 10 | 0.1723 |
| 15 | 0.1693 |
| 20 | 0.1664 |
| 25 | 0.1636 |
| 30 | 0.1609 |
| 35 | 0.1583 |
| 40 | 0.1558 |
| 45 | 0.1533 |
| 50 | 0.1509 |
Answered by
Dr Etienne Jooken
Chemistry
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.