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Solubility Honors Chemistry Mrs. Jacobus Components of a Solution Solute is the substance being dissolved – powder Solvent is the dissolving agent – water Solute Dissolve Solvent Solubility The amount of solute that will dissolve in a given amount of solvent. Soluble vs. insoluble May vary with solvent “Like dissolves like” Polar and Nonpolar • A polar bond is a covalent bond between two atoms where the electrons forming the bond are unequally distributed • A nonpolar bond is a covalent bond between two atoms where the electrons forming the bond are equally distributed Nonpolar Molecule (CH4) Polar Molecule (H2O) “Like dissolves like” Two substances with similar intermolecular forces (force between two molecules) are likely to be soluble in each other. • non-polar molecules are soluble in non-polar solvents CCl4 in C6H6 • polar molecules are soluble in polar solvents C2H5OH in H2O • ionic compounds are more soluble in polar solvents NaCl in H2O or NH3 (l) 12.2 Factors Affecting Solubility – Temperature – Pressure Solubility is the amount of solute that will dissolve in a given amount of solvent at a given temperature or pressure. Factors Affecting the Rate of Dissolution – Stirring – Temperature – Particle size/Surface area A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature. Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate. 12.1 Solubility Concentration Units The concentration of a solution is the amount of solute present in a given quantity of solvent or solution. Percent by Mass mass of solute x 100% % by mass = mass of solute + mass of solvent mass of solute x 100% = mass of solution Mole Fraction (X) moles of A XA = sum of moles of all components 12.3 Concentration Units Continued Molarity (M) M = moles of solute liters of solution Molality (m) m = moles of solute mass of solvent (kg) 12.3 What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is 0.927 g/mL? moles of solute moles of solute m = M = mass of solvent (kg) liters of solution Assume 1 L of solution: 5.86 moles ethanol = 270 g ethanol 927 g of solution (1000 mL x 0.927 g/mL) mass of solvent = mass of solution – mass of solute = 927 g – 270 g = 657 g = 0.657 kg moles of solute m = mass of solvent (kg) = 5.86 moles C2H5OH = 8.92 m 0.657 kg solvent 12.3 Saturated, Unsaturated & Supersaturated Ex.1) If 10.0 g of KCl is dissolved in 100.0 g of water at 20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ________________________________________. unsaturated Ex.2) If 10.0 g of KClO3 is stirred into 100.0 g of water at 20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? ________________________________________. saturated with about 1 g of undissolved KClO3 Ex.3) If 10.0 g of KClO3 is dissolved in 100.0 g of water at 20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? supersaturated ________________________________________. Saturated, Unsaturated & Supersaturated Ex.4) If 100.0 g of KI is stirred into 100.0 g of water at 20.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? unsaturated ______________________________________ Ex.5) If 100.0 g of KNO3 is stirred into 100.0 g of water 60.0oC, then would the solution be described as unsaturated, saturated, or supersaturated? unsaturated ______________________________________ at Ex.6) How many grams of KNO3 will exactly saturate g of H2O at 20.0oC? ______________ g ≈70 200.0 Temperature and Solubility Solid solubility and temperature solubility increases with increasing temperature solubility decreases with increasing temperature 12.4 Temperature and Solubility O2 gas solubility and temperature solubility usually decreases with increasing temperature 12.4 Watch the following video: http://www.youtube.com/watch?v=XSGvy2FPfCw What kind of a solution is it? Need more help? • http://www.wwnorton.com/college/chemistry/gil bert2/tutorials/interface.asp?chapter=chapter_0 4&folder=saturated_solutions – Norton tutorial on solubility • http://www.youtube.com/watch?v=zjIVJh4JLNo& edufilter=d3ViuWqXvxQy1rRgssBz8Q – Basic solubility • http://www.youtube.com/watch?v=4VltXjR64SU &edufilter=d3ViuWqXvxQy1rRgssBz8Q – Molarity vs. Molality