2 15.1 SolubilitySolution: homogeneous mixture or mixture in which components are uniformly intermingledSolute: substance that is being dissolved in solventSolvent: substance that dissolves solvent and present in a large amountAqueous solutions: solutions with water as the solvent
4 15.2 Solution Composition: An Introduction Saturated: A solution in which the maximum amount of solvent has been dissolved. Any more solute added will sit as crystals on the bottom of the containerUnsaturated: A solution in which more of solute can be dissolvedConcentrated: a relative large amount of solute is being dissolved in solventDiluted: a relative small amount of solute is being dissolved in solvent
5 15.3 Solution Composition: Mass Percent mass of soluteMass percent (m/m%) = x 100mass of solution
6 ExamplesA solution is prepared by mixing 1.00 g of ethanol, C2H5OH, with g water. Calculate the mass percent of ethanol in this solutionA 135 g sample of seawater is evaporated to dryness, leaving 4.73 g of solid residue (the salts formerly dissolved in the seawater). Calculate the mass percent of solute present in the original seawater
7 Example: Determine Mass of Solute Although milk is not a true solution (it is really a suspension of tiny globules of fat, protein, and other substrates in water), it does contain a dissolved sugar called lactose. Cow’s milk typically contains 4.5 % by mass of lactose, C12H22O11. Calculate the mass of lactose present in 175 g of milk
8 15.4 Solution CompositionMolarity: the number moles of solute per volume of solution in litersmoles of soluteMolarity =Liters of solutionunit = moles/L or M (molar)Standard solution: is a solution whose concentration is accurately known.
9 ExamplesCalculate the molarity of a solution prepared by dissolving 11.5 g of solid NaOH in enough water to make 1.50 L of solutionCalculate the molarity of a solution prepared by dissolving 1.56 g of gaseous HCl into enough water to make 26.8 mL of solutionDetermine how much volume (in ml) will be needed to dissolved 2.50 g of solid NaCl to make 0.050M solution.
10 E.g Solution Composition: Calculating Ion Concentration Give the concentration of all the ions in each of the following solutions:0.50 M Co(NO3)21.0 M FeCl3
11 E.g Solution Composition: Calculating Number moles from Molarity How many moles of Ag+ ions are present in 25.0 mL of a 0.75 M AgNO3 solution?How many moles of Na+ ions are present in 42.0 mL of 0.350M NaCl?
12 Examples: Calculating mass from molarity To analyze the alcohol content of a certain wine, a chemist needs 1.00L of an aqeuous M K2Cr2O7 (potassium dichromate) solution. How much solid K2Cr2O7 (molar mass = g) must be weighed out to make this solution?Formalin is an aqueous solutions of formaldehyde, HCHO,, used as a preservative for biological speciments. How many grams of formaldehyde must be used to prepare 2.5 L of 12.3 M formalin?
13 15.5 DilutionReducing the original concentration of a chemical solutionA process of transferring solution to achieve a the desired molarity by diluting with solventMoles of solute after dilution = moles of solute before dilutionFormula M1 V1 = M2 V2
14 ExamplesWhat volume of 16 M sulfuric acid must be used to prepare 1.5L of 0.10 M of H2SO4 solution?Calculate the new molarity if a dilution is made for:25.0 ml of water is added to 10.0 mL of M CaCl2
15 15.6 Stoichiometry of Solution Reactions Steps for solving stoichiometric problems involving solutionsStep 1: Write a balanced equation for the reaction. For each reactions involving ions, it is best to write the net ionic equation.Step 2: Calculate the moles of reactantStep 3: Determine which reactant is limitingStep 4: Calculate the moles of other reactants or products, as requiredStep 5: Convert to grams or other units, if required
16 ExamplesWhen Ba(NO3)2 and K2CrO4 react in aqueous solution, the yellow solid BaCrO4 is formed. Calculate the mass of BaCrO4 that forms when 3.50 x 10-3 mole of solid Ba(NO3)2 is dissolved in 265 mL of M K2CrO4 solution
17 ExamplesWhen aqueous solutions of Na2SO4 and Pb(NO3)2 are mixed, PbSO4 precipitates. Calculate the mass of PbSO4 formed when 1.25 L of M Pb(NO3)2 and 2.00 L of M Na2SO4 are mixed
18 Neutralization Reaction Use stoichiometry to determine how much of acid or base must be used to reach neutralizationStrong acid: HCl(aq) H+(aq) + Cl-(aq)Strong base: NaOH(s) Na+(aq) + -OH(aq)Net equation: H+(aq) + -OH(aq) H2O(l)
19 ExampleWhat volume of a M HCl solution is needed to neutralize 25.0 mL of a M NaOH?Calculate the volume of 0.10 M HNO3 needed to neutralize 125 mL of MKOH
20 15.8 Solution Composition: Normality Normality is another unit of concentration sometime used when dealing with acid and baseH+ and –OHEquivalent of an acid: the mount of acid that can be furnish 1 mol of H+ ionsEquivalent of a base: the amount of that base that can furnish 1 mol of –OH ions
22 Solution Stoichiometry: Calculating Equivalent Weight Phosphoric acid, H3PO4 can furnish three H+ ions per molecule. Calculate the equivalent weight of H3PO4.Calculate the equivalent weight of HBr
23 Normality (N)Normality (N) = number of equivalent of solute per liter of solutionKnowing Normality can help us calculateThe number of equivalentsThe volume of solution
24 Calculating Normality A solution of sulfuric acid contains 86 g of H2SO4 per liter of solution. Calculate the normality of this solutionCalculate the normality of a solution containing 23.6 g of KOH in 755 ml of solution
25 NeutralizationThe number of H+ ions furnished by the sample of acid is the same as the number of –OH ions furnished by the sample of basereacts exactly withn equiv acid n equiv baseNacid x Vacid = Nbase x Vbase