CH302%20Zumdahl%20Chapter%2017a%20(posting)%20solutions%20sp08

CH302%20Zumdahl%20Chapter%2017a%20(posting)%20solutions%20sp08

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1 CHAPTER 17a Properties of Solutions 2 Solutions ± Solutions are homogeneous mixtures of two or more substances. ² Dissolving medium is called the solvent solvent . ± Water will be the main solvent for this chapter. ± Water is known as the universal solvent. ± Many chemical reactions occur in aqueous solutions. ² Dissolved species are called the solute solute . 3 Solutions ± There are three states of matter (solid, liquid, and gas), which when mixed two at a time gives different kinds of mixtures. .
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4 Solutions ± Largest solutions on Earth are the oceans. ² 1.4 x 10 21 kg of the Earth’s surface ² High concentrations of dissolved salts 5 Solutions ± A solution has variable composition, that is, the relative amounts of solutes and solvent must be specified. ± Qualitatively: ² A dilute solution is composed of a little amount of solute relative to the solvent. ² A concentration solution has a large amount of solute relative to the solvent. 6 Solutions When a solvent has dissolved its limit of solute, the dissolved and undissolved solutes are in equilibrium at constant temperature and pressure. dissolved solute undissolved solute ± At this point, the solution is saturated . ± If a solvent has not reached its limit of solute, the solution is unsaturated . ± If more than the limit of solute is dissolved in a solvent it is supersaturated . (This is an unstable solution.)
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7 Concentration of Solutions Molarity of the Solution ± Concentration based on moles of solute in a liter of solution. ± This is the “workhorse” formula for determining the composition (concentration) of solutions . 8 Concentration of Solutions Molarity or Molar Concentration (M) moles of solute molarity liters of solution = 9 Concentration of Solutions Examples: 1) Calculate the molarity of a solution prepared by dissolving 11.5 g of solid NaOH in enough water to produce a 1.50 L NaOH solution.
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10 Concentration of Solutions First, we must determine the number of moles of sodium hydroxide in the 11.5 g. 1 11.5 0.288 40.0 0.288 0.192 '1 . 5 0 ' mol NaOH gNaOHx mo lNaOH gNaOH mol solute mol NaOH M MNaOH Lsol n L sol n = == = 11 Concentration of Solutions 2) How many grams of gaseous HCl is required to produce 26.8 mL of a 1.59 M HCl solution? () ' 1.59 0.0268 ' 1.59 0.0268 0.0426 36.5 0.0426 1.56 1 mol HCl M LHC lso ln mol HCl M mol Lm o l H C l L mol of HCl gHC l mol HCl g HCl mol HCl = =  =   = = 12 Solution Composition Percent by mass (m/m or w/w) % 100 : %1 0 0 mass of solute by mass of solute mass of solution Since the solution is defined as the solute solvent mass of solute by mass of solute mass of solute mass of solvent + +
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13 Solution Composition 1) Cow’s milk typically contains 4.5 % sugar lactose (C 12 H 22 O 12 ). What is the mass of lactose present in 175 g of milk? 4.5 % 100% 175 0.045 175 175 (0.045) 7.9 xg lactose x g milk g milk g gl a c t o s e = = = = 14 Solution Composition 2) Lactose, (C 12 H 22 O 12 ), is a naturally occurring sugar found in mammalian milk. How many grams of lactose must be added to 25.0 g of water to prepare 5.00% (m/m) aqueous solution of lactose?
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This note was uploaded on 09/20/2008 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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CH302%20Zumdahl%20Chapter%2017a%20(posting)%20solutions%20sp08

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