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Matter Notes X Law of Definite Proportions – or Constant Composition elemental composition of a pure substance is always the same, ex. Water (Proust) X Law of Multiple Proportions – (Dalton) If two elements form more than one compound, the masses of one that combine with a given mass of the other, are in the ratio of small whole numbers. Ex. Water vs. Hydrogen Peroxide X Law of Conservation of Mass (Lavoisier) Total mass before a chemical rxn = total mass after chem. Rxn. X Solutions – Homogeneous Mixtures – Single phase Solute – Substance that is dissolved Solvent – Substance doing the dissolving Solubility affected by nature of the solute, nature of solvent, Temperature Dissolving illustrates equilibrium concept – point at which rate of dissolution = rate of return to solid solute At equilibrium solution is saturated – max amount of solid is dissolved Unsaturated – Can dissolve more, not at equilibrium Supersaturated – Solution holds more solute than normally dissolved in a saturated sol’n at the same temp. – unstable, crystallizes out Gas solubility decreases with increased temp – Reducing the Pressure at a liquid’s surface enables gas to escape Ex. Carbon dioxide in soda – effervescence P1/S1 = P2/S2 same T Henry’s Law Concentration Dilute- Small amount of solute per volume of sol’n Concentrated – Large amount of solute per volume of sol’n Can express concentration in terms of mass percentage (mass solute per 100g sol’n) or by using mass volume relationships (1.00gsugar in 1.00L = 1.00g/L) Ex. Commercial Sulfuric Acid is sold as a 98% sol’n in water, having a D=1.84g/mL. The solute in solution is the sulfuric acid. Calculate the grams of solute in: a. 1.00L of sol’n b. 200. mL of sol’n a. 1.00L has a mass of 1.00L x 1000mL/L x 1.84g/mL = 1840g Since it is 98% by mass: 1840g x .98 = 1800g b. ?g solute = 200.mL x 1.00 L sol’n/1000mL x 1840g sol’n/L sol’n x 98 g solute/100g sol’n = 360g solute Suspension – Heterogeneous, multi-phase system. Can be Separated by filtration ex: muddy water Colloid – Particles suspended as in a suspension but do not separate upon standing; particles are of substantial enough size to reflect light (Tyndall Effect) – The scattering of a beam of visible light by the particles in a colloidal dispersion. Ex. – milk (emulsion) fog (Tyndall as headlights of a car disperse light) mist, blood, gelatins, jelly whipped cream paint smoke butter marshmallow Continuous phase – dispersion medium Dispersed phase – internal phase particles are usually invisible