Chemistry Solutions and Concentrations

Solutions

• Solvent: The component present in the largest amount, often water in aqueous solutions.
• Solute: The component present in the smallest amount, dissolved in the solvent.
• Solubility Determination: Comparing solute-to-solvent ratios in various solutions at consistent temperatures.
• Concentration (% m/v): Calculated as (mass of solute (g) / volume of solution (mL)) × 100.

Concentrations

• Mass/Volume (% m/v): (Mass of solute (g) / Volume of solution (mL)) × 100
• Mass/Mass (% m/m): (Mass of solute (g) / Total mass of solution (g)) × 100
• Volume/Volume (% v/v): (Volume of solute (mL) / Total volume of solution (mL)) × 100
• Dilution: C₁V₁ = C₂V₂ (used to adjust concentration levels, where C is concentration and V is volume)

Molarity and Dilutions

• Molarity (M): Moles of solute / Liters of solution
• Dilution Problems: Combine stock solution and water volumes to calculate final concentration using M₁V₁ = M₂V₂
• Ionic Solutions: Calculate ion concentration by multiplying molarity by the number of ions dissociated per formula unit.

Precipitation Reactions

• Net Ionic Equations: Simplify reactions to show only the reacting ions forming a precipitate.
• Stoichiometry: Calculate precipitate mass using moles of limiting reagent × molar mass of precipitate.
• Solubility Rules:
• Nitrates (NO₃⁻), alkali metals, and ammonium salts are soluble.
• Sulfates (SO₄²⁻) and halides (Cl⁻, Br⁻, I⁻) are soluble except with Pb, Ba, or Hg.

Acids and Bases

• Arrhenius Acid/Base:
• Acid: Increases [H⁺] ions in solution.
• Base: Increases [OH⁻] ions in solution.
• pH Indicators:
• Phenol red: Yellow in acidic, red in basic.
• Phenolphthalein: Colorless in acidic, pink in basic.
• Titration: Use M₁V₁ = M₂V₂ to find unknown concentrations.
• Example: HCl + NaOH → NaCl + H₂O