Year 11 / Intermolecular forces and gases
Different attractions, different journeys.
Chromatography separates components because they spend different proportions of time in the mobile and stationary phases. A component more strongly retained by the stationary phase travels less far under otherwise identical conditions.
Rf is the distance from the origin to the centre of a spot divided by solvent-front distance. Compare values only under the same experimental conditions. A matching spot supports an identification but does not prove it; two compounds may co-migrate.
Retention slows a spot
Explore the relationship
Illustrative Rf = 1/(1 + retention factor). Distances are measured from the same baseline.
Spot distance / cm
Tap or focus a plotted point to read its values.
View plotted data as a table
| Series | Solvent front / cm | Spot distance / cm |
|---|---|---|
| Spot distance / cm | 0 | 0 |
| Spot distance / cm | 0.133333 | 0.0666667 |
| Spot distance / cm | 0.266667 | 0.133333 |
| Spot distance / cm | 0.4 | 0.2 |
| Spot distance / cm | 0.533333 | 0.266667 |
| Spot distance / cm | 0.666667 | 0.333333 |
| Spot distance / cm | 0.8 | 0.4 |
| Spot distance / cm | 0.933333 | 0.466667 |
| Spot distance / cm | 1.06667 | 0.533333 |
| Spot distance / cm | 1.2 | 0.6 |
| Spot distance / cm | 1.33333 | 0.666667 |
| Spot distance / cm | 1.46667 | 0.733333 |
| Spot distance / cm | 1.6 | 0.8 |
| Spot distance / cm | 1.73333 | 0.866667 |
| Spot distance / cm | 1.86667 | 0.933333 |
| Spot distance / cm | 2 | 1 |
| Spot distance / cm | 2.13333 | 1.06667 |
| Spot distance / cm | 2.26667 | 1.13333 |
| Spot distance / cm | 2.4 | 1.2 |
| Spot distance / cm | 2.53333 | 1.26667 |
| Spot distance / cm | 2.66667 | 1.33333 |
| Spot distance / cm | 2.8 | 1.4 |
| Spot distance / cm | 2.93333 | 1.46667 |
| Spot distance / cm | 3.06667 | 1.53333 |
| Spot distance / cm | 3.2 | 1.6 |
| Spot distance / cm | 3.33333 | 1.66667 |
| Spot distance / cm | 3.46667 | 1.73333 |
| Spot distance / cm | 3.6 | 1.8 |
| Spot distance / cm | 3.73333 | 1.86667 |
| Spot distance / cm | 3.86667 | 1.93333 |
| Spot distance / cm | 4 | 2 |
| Spot distance / cm | 4.13333 | 2.06667 |
| Spot distance / cm | 4.26667 | 2.13333 |
| Spot distance / cm | 4.4 | 2.2 |
| Spot distance / cm | 4.53333 | 2.26667 |
| Spot distance / cm | 4.66667 | 2.33333 |
| Spot distance / cm | 4.8 | 2.4 |
| Spot distance / cm | 4.93333 | 2.46667 |
| Spot distance / cm | 5.06667 | 2.53333 |
| Spot distance / cm | 5.2 | 2.6 |
| Spot distance / cm | 5.33333 | 2.66667 |
| Spot distance / cm | 5.46667 | 2.73333 |
| Spot distance / cm | 5.6 | 2.8 |
| Spot distance / cm | 5.73333 | 2.86667 |
| Spot distance / cm | 5.86667 | 2.93333 |
| Spot distance / cm | 6 | 3 |
| Spot distance / cm | 6.13333 | 3.06667 |
| Spot distance / cm | 6.26667 | 3.13333 |
| Spot distance / cm | 6.4 | 3.2 |
| Spot distance / cm | 6.53333 | 3.26667 |
| Spot distance / cm | 6.66667 | 3.33333 |
| Spot distance / cm | 6.8 | 3.4 |
| Spot distance / cm | 6.93333 | 3.46667 |
| Spot distance / cm | 7.06667 | 3.53333 |
| Spot distance / cm | 7.2 | 3.6 |
| Spot distance / cm | 7.33333 | 3.66667 |
| Spot distance / cm | 7.46667 | 3.73333 |
| Spot distance / cm | 7.6 | 3.8 |
| Spot distance / cm | 7.73333 | 3.86667 |
| Spot distance / cm | 7.86667 | 3.93333 |
| Spot distance / cm | 8 | 4 |
Explore: Increase stationary-phase retention and compare spot travel.
A spot travels 3.0 cm and the solvent front travels 5.0 cm.
- Rf = .
- Rf = 0.60, with no unit.
Assumed knowledge
Ratios and solubility.
Learning checkpoints & source
YOUR LEARNING CHECKPOINT- Explain separation into stationary and mobile phases.
- Calculate Rf and interpret evidence for identity or purity.
READY TO TRY IT?