CHEM_1017_ch._4 - SOLUTIONS Solution a homogeneous mixture...

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SOLUTIONS Solution: a homogeneous mixture of two or more substances. Solute: the substance usually present in the smaller amount. Solvent: the substance usually present in the largest amount.
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TYPES OF SOLUTIONS 1. Solid in liquid – sugar dissolved in H 2 O 2. Liquid in liquid – alcohol dissolved in H 2 O 3. Gas in liquid – CO 2 dissolved in Coca Cola 4. Gas in gas – air (O 2 dissolved in N 2 ) 5. Solid in solid – metal alloys, solder
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Concentration of a solution: the amount of solute present in a given amount of solvent. Solubility of a solute: the maximum amount of solute that can be dissolved in a given quantity of solvent at a specific temperature. When a solution contains this maximum amount of solute, the solution is said to be saturated . In general, the solubility of a solute in a particular solvent will vary with temperature. For most solid and liquid solutes, the solubility increases as the temperature increases. (You can dissolve more sugar in a cup of hot coffee than in a cup of cold coffee.) For gaseous solutes, the solubility generally decreases with increasing temperature. (Coca Cola starts to “fizz” when you heat it up – i.e. the dissolved CO 2 comes out of solution).
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WAYS TO EXPRESS CONCENTRATION 1. wt % e.g. 5 g of sugar dissolved in 23 g water 2. vol. % e.g. 5 mL of alcohol dissolved in 23 mL water wt. solute wt. solute 100 100 wt. solution wt. solute wt. solvent × = × + 5 100 17.9% 23 5 × = + vol. solute 100 vol. solution × 5 100 17.9% 23 5 × = +
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3. mole % e.g. 10 g NaCl dissolved in 15 g water 4. mole fraction (X i ) same as mole % but without the 100 moles solute 100 moles solute moles solvent × + NaCl 10 moles 0.171 58.5 = = 2 H O 15 moles 0.833 18 = = 0.171 mole % NaCl 100 17.0% 0.171 0.833 = × = + NaCl 0.171 X .170 0.171 0.833 = = +
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By far, the most widely used unit of concentration in chemistry is molarity . 5. # moles = liter x Molarity Virtually all solution concentration problems can be solved with one of these three corollaries. # moles solute molarity (M) liter of solution = # moles liter Molarity =
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In most chemical reactions, we usually work with less than molar quantities of reactants, and less than liters of solution. A more convenient unit can be obtained by dividing both the numerator and denominator by 1000, i.e. mmole and mL. # mmoles = mL x Molarity mmoles solute molarity (M) mL of solution = # mmoles mL Molarity =
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Describe how you would prepare 250 mL of 0.707 M NaNO 3 solution. You are given the volume (mL) and the concentration (M),
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This note was uploaded on 10/13/2010 for the course CHEM 101 taught by Professor Crago during the Spring '06 term at Loyola New Orleans.

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CHEM_1017_ch._4 - SOLUTIONS Solution a homogeneous mixture...

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