Case 1
- Van 't Hoff factor i
- 1
- Molar concentration M (mol/L)
- 0.1mol/L
- Temperature T (K)
- 310K
2.5438atm
Open with these valuesOsmotic Pressure Calculator
2.5438atm
Result: 2.5438 atmΠ = i × M × R × T, with R = 0.082057 L·atm/(mol·K) and the temperature in kelvin, gives the pressure in atmospheres. 0.1 mol/L glucose at 310 K is 2.5438 atm, or 257.75 kPa. Multiply by 101.325 for kilopascals; add 273.15 to a Celsius reading first.
The numbers at a glance
Held fixed: Van 't Hoff factor i 1.00, Molar concentration M (mol/L) 0.1000 mol/L.
| Temperature T (K) (K) | Result (atm) |
|---|---|
| 100.00 | 0.8206 |
| 200.00 | 1.6411 |
| 300.00 | 2.4617 |
| 310.00Your value | 2.5438 |
| 400.00 | 3.2823 |
| 500.00 | 4.1029 |
Worked examples
Case 2
- Van 't Hoff factor i
- 2
- Molar concentration M (mol/L)
- 0.5mol/L
- Temperature T (K)
- 298.15K
24.4653atm
Open with these valuesCase 3
- Van 't Hoff factor i
- 3
- Molar concentration M (mol/L)
- 0.2mol/L
- Temperature T (K)
- 310K
15.2626atm
Open with these valuesHow it's calculated
Π = i × M × R × T, R = 0.082057 L·atm/(mol·K)
- StepEnter how many particles one formula unit splits into: 1 glucose, 2 NaCl, 3 CaCl₂.
- StepEnter the molarity in moles per litre of solution.
- StepEnter the absolute temperature in kelvin — Celsius plus 273.15.
- ResultRead the pressure in atmospheres; × 101.325 gives kilopascals.
Reference table
| i, M, T | Same pressure in kPa | Π in atm |
|---|---|---|
| 1, 0.05, 273.15 | 113.55 | 1.1207 |
| 1, 0.1, 310 | 257.75 | 2.5438 |
| 3, 0.2, 310 | 1546.48 | 15.2626 |
| 2, 0.5, 298.15 | 2478.95 | 24.4653 |
| 2, 1, 300 | 4988.66 | 49.2342 |
Questions
How do I calculate osmotic pressure?
Multiply the van 't Hoff factor by the molarity, the gas constant R = 0.082057 L·atm/(mol·K), and the absolute temperature. For 0.1 mol/L glucose at 310 K that is 1 × 0.1 × 0.082057 × 310 ≈ 2.5438 atm.
Why does the temperature have to be in kelvin?
The equation mirrors the ideal gas law, which uses absolute temperature measured from absolute zero. Convert Celsius by adding 273.15, so body temperature at 37 °C is 310.15 K.
What is the van 't Hoff factor i?
It is how many particles one formula unit produces on dissolving: 1 for non-electrolytes such as glucose, 2 for NaCl, 3 for CaCl₂. More particles mean more pressure at the same concentration, which is why the calculator asks rather than assuming a substance.
How do I convert the answer to kilopascals or bar?
Multiply the atmospheres by 101.325 for kilopascals, or by 1.01325 for bar. So 2.5438 atm is about 257.75 kPa.
How accurate is the van 't Hoff equation?
It is at its best for dilute, ideal solutions. In concentrated electrolytes ion pairing lowers the effective van 't Hoff factor, so the calculated pressure is an upper estimate.
Sources and last check
Information, not professional advice.