A chemist wants to separate and identify a mixture of substances by using paper chromatography. The diagram shows the apparatus used. The solvent is water. The chemist leaves the solvent front to reach the top of the paper before removing the paper from the solvent. What problem does this lead to?
- AThis causes the spot nearest the bottom of the paper to catch up with the spot above it.
- BThis makes it impossible to calculate $R_f$ values.
- CThis makes it impossible to use a locating agent.
- DThis results in a safety hazard caused by solvent fumes.