Raoult's Law Calculator
Calculate vapor pressure of solution using Raoult's law: P-solution = x-solvent * P-pure. Find vapor pressure lowering, mole fraction, or identify ideal solution behavior.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Raoult's Law Calculator | — | Psoln = xsolvent·P°solvent | Pa or mmHg |
Step-by-Step Examples
0.100 mol sucrose in 900 g water (50 mol H2O) at 25 C. P0(H2O)=23.76 mmHg.
- n(water)=900/18.02=49.94 mol, n(sucrose)=0.100
- x(water)=49.94/(49.94+0.100)=0.998
- P = 0.998 x 23.76 = 23.71 mmHg
- dP = 23.76-23.71 = 0.05 mmHg small effect
x(water)=0.50 in mixture. P0(water)=23.76, P0(ethanol)=44.8 mmHg at 25 C.
- P(water) = 0.50 x 23.76 = 11.88 mmHg
- P(ethanol) = 0.50 x 44.8 = 22.4 mmHg
- P(total) = 11.88+22.4 = 34.28 mmHg (Dalton)
P(soln)=20.0 mmHg. P0(water)=23.76 mmHg. Find x(solute).
- x(solvent) = P/P0 = 20.0/23.76 = 0.842
- x(solute) = 1 - 0.842 = 0.158
Real-World Applications
Common Mistakes to Avoid
Raoult law uses mole fraction x = n_solvent / n_total. Not g/g or g/L.
Raoult law is exact only for ideal solutions (same intermolecular forces). Real solutions deviate, especially alcohol-water.
Positive deviation (P > Raoult): solvent-solvent interactions stronger than solvent-solute (e.g., acetone-hexane). Negative: solvent-solute stronger (acetone-chloroform).
Frequently Asked Questions
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Formula Explorer connections
Interpretation: This relationship connects pressure, volume, temperature, amount or phase composition for gases and volatile mixtures. Assumption: Use absolute temperature and compatible pressure-volume units. Ideal behavior weakens at high pressure, low temperature, strong intermolecular attraction or near phase change.