- Rf = distance moved by substance ÷ distance moved by solvent front (always 0 to 1, no units)
- One spot on a chromatogram = pure substance; multiple spots = mixture
- Match unknown Rf to reference Rf to identify an unknown substance
- Instrumental methods are more accurate, more sensitive, and faster than traditional chemical tests
- Flame emission spectroscopy identifies metals from their characteristic line spectra
- Li⁺ = crimson, Na⁺ = yellow, K⁺ = lilac, Ca²⁺ = orange-red
- Line spectra are unique to each element (like a fingerprint)
This key facts covers Key Facts at a Glance within Instrumental Analysis for GCSE Chemistry. Revise Instrumental Analysis in Chemical Analysis for GCSE Chemistry with 6 exam-style questions and 6 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 6 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Instrumental Analysis
Which formula correctly calculates the Rf value in chromatography?
State two advantages of using instrumental methods of analysis compared with traditional chemical tests.
Quick recall flashcards
In paper chromatography, what does the number of spots on a chromatogram tell you about purity?
One spot → pure substance (single component)
Multiple spots → mixture / impure sample (multiple components, each with different Rf)
What is the formula for calculating the Rf value in chromatography?
Rf = distance moved by substance ÷ distance moved by solvent front
Always between 0 and 1. No units.