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Common Types of Solution

Common Types of Solution
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Dr.SamuelHunt,United Arab Emirates,Teacher
Published Date:21-07-2017
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Chapter 13 Solutions www.ThesisScientist.comSolutions • What is in a solution • How do we make them • How do we dilute them • Does pressure and temperature make a difference • How do solutions mix in our body www.ThesisScientist.comTragedy in Cameroon • Lake Nyos  Lake in Cameroon, West Africa.  On August 22, 1986, 1,700 people and 3,000 cattle died. • Released carbon dioxide cloud.  CO seeps in from underground 2 and dissolves in lake water to levels above normal saturation.  Though not toxic, CO is heavier 2 than air—the people died from asphyxiation. www.ThesisScientist.comTragedy in Cameroon: A Possible Solution • Scientists have studied Lake Nyos and similar lakes in the region to try and keep such a tragedy from reoccurring. • Currently, they are trying to keep the CO levels in the lake 2 water from reaching the very high supersaturation levels by venting CO from the lake 2 bottom with pipes. www.ThesisScientist.comSolutions • Homogeneous mixtures. Appears to be one substance, though really contains multiple materials. E.g., air and lake water. • Heterogeneous mixtures Appears to have two or more substances, you can see the individual components Chocolate chip cookies, people in a room, your neighborhood with houses, cars and trees www.ThesisScientist.comSolutions, Continued • Solute is the dissolved substance. Seems to “disappear.” “Takes on the state” of the solvent. • Solvent is the substance solute dissolves in. Does not appear to change state. • When both solute and solvent have the same state, the solvent is the component present in the highest percentage. • Solutions in which the solvent is water are called aqueous solutions. www.ThesisScientist.comCommon Types of Solution Solute Solvent Solution phase phase phase Example Air (mostly N and O ) Gaseous solutions Gas Gas 2 2 Gas Liquid Soda (CO in H O) 2 2 Vodka (C H OH in H O) Liquid solutions Liquid Liquid 2 5 2 Seawater (NaCl in H O) 2 Solid Liquid Brass (Zn in Cu) Solid solutions Solid Solid www.ThesisScientist.comSolubility • When one substance (solute) dissolves in another (solvent) it is said to be soluble. Salt is soluble in water. Bromine is soluble in methylene chloride. • When one substance does not dissolve in another it is said to be insoluble. Oil is insoluble in water. • The solubility of one substance in another depends on two factors: nature’s tendency towards mixing and the types of intermolecular attractive forces. www.ThesisScientist.comWill It Dissolve? • Chemist’s rule of thumb: Like dissolves like • A chemical will dissolve in a solvent if it has a similar structure to the solvent. • When the solvent and solute structures are similar, the solvent molecules will attract the solute particles at least as well as the solute particles to each other. www.ThesisScientist.comClassifying Solvents Structural Solvent Class feature Water, H O Polar O-H 2 Ethyl alcohol, C H OH Polar O-H 2 5 Acetone, C H O Polar C=O 3 6 Nonpolar Toluene, C H C-C and C-H 7 8 Nonpolar Hexane, C H C-C and C-H 6 14 Nonpolar Diethyl ether, C H O C-C, C-H, 4 10 and C-O www.ThesisScientist.comWill It Dissolve in Water? • Ions are attracted to polar solvents.  Many ionic compounds dissolve in water. Generally, if the ions total charges 4. • Polar molecules are attracted to polar solvents.  Table sugar, ethyl alcohol, and glucose all dissolve well in water. Have either multiple OH groups or little CH. • Nonpolar molecules are attracted to nonpolar solvents. b-carotene (C H ) is not water soluble; it dissolves in fatty 40 56 (nonpolar) tissues. • Many molecules have both polar and nonpolar structures—whether they will dissolve in water depends on the kind, number, and location of polar and nonpolar structural features in the molecule. www.ThesisScientist.comSalt Dissolving in Water www.ThesisScientist.comSolvated Ions When materials dissolve, the solvent molecules surround the solvent particles due to the solvent’s attractions for the solute. This process is called solvation. Solvated ions are effectively isolated from each other. www.ThesisScientist.comPractice—Decide if Each of the Following Will Be Significantly Soluble in Water. • • p po otassiu tassium m io iod did ide, e, KI KI soluble. • • o octan ctane, e, C C H H insoluble. 8 8 18 18 • • m meth ethan ano ol, l, CH CH OH OH soluble. 3 3 • • co cop pp per, er, Cu Cu insoluble. • • cety cetyl l alcoh alcoho ol, l, CH CH (CH (CH ) ) CH CH OH OH insoluble. 3 3 2 2 14 14 2 2 • • iron iron(I (III II) ) su sulf lfid ide, e, Fe Fe S S insoluble. 2 2 3 3 www.ThesisScientist.comSupersaturated Solution A supersaturated solution has more dissolved solute than the solvent can hold. When disturbed, all the solute above the saturation level comes out of solution. www.ThesisScientist.comAdding Solute to various Solutions Unsaturated Saturated Supersaturated www.ThesisScientist.comElectrolytes • Electrolytes are substances whose aqueous solution is a conductor of electricity. • In strong electrolytes, all the electrolyte molecules are dissociated into ions. • In nonelectrolytes, none of the molecules are dissociated into ions. • In weak electrolytes, a small percentage of the molecules are dissociated into ions. www.ThesisScientist.comSolubility and Temperature • The solubility of the solute in the solvent depends on the temperature.  Higher temperature = Higher solubility of solid in liquid.  Lower temperature = Higher solubility of gas in liquid. www.ThesisScientist.comChanging Temperature = Changing Solubility • When a solution is saturated, it is holding the maximum amount of solute it can at that temperature. • If the temperature is changed, the solubility of the solute changes. If a solution contains 71.3 g of NH Cl in 100 g 4 of water at 90 C, it will be saturated. If the temperature drops to 20 C, the saturation level of NH Cl drops to 37.2 g. 4 Therefore, 24.1 g of NH Cl will precipitate. 4 www.ThesisScientist.comPurifying Solids: Recrystallization • Formation of the crystal lattice tends to reject impurities. • To purify a solid, chemists often make a saturated solution of it at high temperature; when it cools, the precipitated solid will have much less impurity than before.