Combustion Analysis and Photoelectron Spectroscopy

What combustion analysis is used for

Finding empirical formula of hydrocarbons (CₓHᵧ) burned to produce CO₂ and H₂O

Steps of combustion analysis

1. Find mass of C from CO₂: mass C = mass CO₂ × (12.01 / 44.01)

2. Find mass of H from H₂O: mass H = mass H₂O × (2.016 / 18.02)

3. Add → total mass of hydrocarbon

4. Convert to moles → find simplest ratio → empirical formula

What to do if oxygen is present

Subtract C + H from total sample mass to find mass of O.

Photoelectron spectroscopy

Measures binding energy of electrons in atoms. Each peak = electrons in a subshell

What photoelectron spectroscopy graph shows

X-axis: Bbnding energy (increases left to right); Y-axis: number of electrons (peak height); peaks grouped by n and ℓ (e.g., 1s, 2s, 2p...)

How to interpret a photoelectron spectroscopy graph

Higher binding energy = closer to nucleus (harder to remove); split peaks = different subshells; relative peak areas = # electrons (e.g., p-orbital peak is 3× taller than s)