Solutions, Mixtures, and Spectrophotometry

$M = \frac{n}{V} = \frac{\text{moles of solute}}{\text{litres of solution}}$

Dilution

$M_1V_1 = M_2V_2$

Soluble: Group 1, NH₄⁺, NO₃⁻, CH₃COO⁻, ClO₄⁻, most halides (except Ag, Pb, Hg), most sulfates (except Ba, Pb, Ca, Sr)

Insoluble: most carbonates, phosphates, sulfides, hydroxides (except Group 1, NH₄⁺, Ba, Ca slightly)

$A = \varepsilon bc$

where:

• $A$ = absorbance (no units)
• $\varepsilon$ = molar absorptivity (L mol⁻¹ cm⁻¹)
• $b$ = path length (cm)
• $c$ = concentration (mol/L)

The relationship is linear — a graph of $A$ vs $c$ gives a straight line through the origin (calibration curve).

Use the calibration curve to determine unknown concentrations.

• Filtration: separate solid from liquid
• Distillation: separate liquids by boiling point
• Chromatography: separate dissolved substances
• Centrifugation: separate by density

• $M = n/V$; dilution: $M_1V_1 = M_2V_2$
• Solubility rules predict precipitation reactions
• Beer-Lambert: $A = \varepsilon bc$; linear relationship for calibration
• Use calibration curves to find unknown concentrations