AP Chemistry · Summary

Unit 3 summary

1. Boiling and melting overcome intermolecular forces, not covalent bonds. Every molecule has London forces; more electrons and more surface contact make them stronger.
2. Hydrogen bonds need an H on N, O or F and a lone pair on N, O or F of a neighbor. Stronger forces mean higher boiling points and lower vapor pressures.
3. Use $PV = nRT$ with kelvin temperature; for one sample, $\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}$. Partial pressure is mole fraction times total pressure.
4. Average kinetic energy depends only on kelvin temperature; real gases depart from ideal at high pressure and low temperature.
5. Molarity is moles per liter of solution; on dilution the moles stay fixed, so $M_1 V_1 = M_2 V_2$. Count every ion a formula releases.
6. Like dissolves like; in chromatography on polar paper, the most polar component moves least.
7. $E = \frac{hc}{\lambda}$; IR changes vibrations, visible and UV move electrons; and $A = \varepsilon b c$, so an error that raises A raises the calculated concentration.