CHEM / A2 level
NMR chemical shifts, integration and splitting constrain hydrogen environments; infrared and mass spectra add complementary evidence. Chromatography separates species by their interactions with two phases.
NMR chemical shifts, integration and splitting constrain hydrogen environments; infrared and mass spectra add complementary evidence. Chromatography separates species by their interactions with two phases.
Planning links an answerable question to controlled measurements, calibration and analysis. Combine spectral clues with the molecular formula, assess uncertainty and propose specific improvements; use supplied data when hazardous work would otherwise be required.
Rf = distance moved by substance / distance moved by solvent front
Distances use the same starting baseline and units.
A spot moves 3.0 cm and solvent front 6.0 cm. Find Rf.
Rf=3.0/6.0=0.50, a dimensionless ratio.
Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.
Use the evidence activity below; no exact PhET model is claimed.
Relative numbers of contributing protons
Peak areas compare populations of protons in different environments.
0.50
Rf=3.0/6.0=0.50, a dimensionless ratio.
No
Rf depends on the stationary phase, solvent and conditions, so comparisons require matching methods.