Transcript Solubility
Solubility and pH Solution = Solute + Solvent Solvation • Process of surrounding solute particles with solvent particles to form a solution Video Like Dissolves Like • Polar substances dissolve polar substances • Nonpolar substances dissolve nonpolar substances EX: Demo Styrofoam (nonpolar) + water (polar) = insoluble Styrofoam (nonpolar) + acetone (nonpolar) = soluble Factors Affecting the Rate of Solvation • To increase solvation of a solid Heat it (↑ temp.) Stir it (agitate the mixture) Crush it (↑ surface area) • To increase solvation of a gas Cool it Increase pressure Temperature and Pressure Change: Solid vs. Gas Pressure Change: Solid vs. Gas Summary Solids dissolve Gases dissolve the best when best when Heated Solution is cold Stirred Pressure is high Crushed Solubility • Maximum amount of solute that will dissolve in a given amount of solvent at a specific temperature and pressure Types of Solutions • Unsaturated – a solution that can dissolve more solute • Saturated – a solution that contains the maximum amount of solute that can dissolve • Supersaturated – a solution that cannot dissolve more solute Practice 1. 80g of NaNO3 in 100g of H20 at 10⁰C UnSaturated 2. 60g of KCl in 100g H20 at 70 ⁰ C Supersaturated 3. 150g of Kl in 100g H2O at 25 ⁰ C Saturated Dissociation of Water • Water splits into H+ & OH• H+ = hydrogen ion • OH- = hydroxide ion pH is a measure of how much H+ is present • 0 - 14 • 7 = neutral • Negative log scale Dissociation of Water Acids • Acids are compounds that add H+ ions to water when in a solution – below pH of 7 Bases • Bases are compounds that add OH- ions to water when in a solution – above pH of 7 pH Scale – Measure of Acids and Bases • When the pH changes from the pH of 7 in the mouth to a pH of 2 in the stomach, how many more times acidic is that ? • 100,000 (power of ten) Neutralization • When acids and bases are mixed they neutralize (cancel) each other Acid Rain What are buffers? *Buffers are substances that maintain a particular pH so that a reaction may occur and at an appropriate rate . *Chemical reactions in living organisms are very sensitive to pH. Buffer Example Ex.:As the chyme moves from the stomach into the small intestine sodium bicarb buffers the pH back up to 6.8 – a quick change of almost a magnitude of 100,000 decrease in acidity