Presentation on theme: "Materials to take notes"— Presentation transcript:
1Materials to take notes Greetings!Mixtures & SolutionsToday you need:Materials to take notes
2The GPS StandardSC7. Students will characterize the properties that describe solutions and the nature of acids and bases.a. Explain the process of dissolving in termsof solute/solvent interactionsb. Observe factors that effect the rate atwhich a solute dissolves in a specificsolvent,c. Express concentrations as molarities,d. Prepare and properly label solutions of specified molar concentration,e. Relate molality to colligative properties.
3Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperaturevaries with temperaturebased on a saturated solution
4SUPERSATURATED SOLUTION SolubilityUNSATURATED SOLUTIONmore solute dissolvesSATURATED SOLUTIONno more solute dissolvesSUPERSATURATED SOLUTIONbecomes unstable, crystals formMaximum amount of a solute that can dissolve in a solvent at a specified temperature and pressure is its solubility.– Solubility is expressed as the mass of solute per volume (g/L) or mass of solute per mass of solvent (g/g) or as the moles of solute per volume (mol/L).– Solubility of a substance depends on energetic factors and on the temperature and, for gases, the pressure.• A solution that contains the maximum possible amount of solute is saturated.• If a solution contains less than the maximum amount of solute, it is unsaturated.When a solution is saturated and excess solute is present, the rate of dissolution is equal to the rate of crystallization.• Solubility increases with increasing temperature — a saturated solution that was prepared at a higher temperature contains more dissolved solute than it would contain at a lower temperature, when the solution is cooled, it can become supersaturated.increasing concentration
5Solubility CurvesSolubility of solids increase with increases in temperature.Solubility of gases in liquids decrease with increasing temperatureWHY?
6The Effect of Temperature on Solubility is dependent on the phase of matter. Solids or liquids dissolved in liquids Gases dissolved in liquidsToSToSAs To , solubilityAs To , solubility
9Think About it…you probably are familiar with the difference between what is called a "weak" solution or a "strong" solution.
10Concentration… The measure of how much solute is dissolved in a specific amount of solvent or solution.a measure of solute-to-solvent ratioconcentrated vs dilute“lots of solute” “not much solute”“watery”Concentration of a solution describes the quantity of a solute that is contained in a particular quantity of solvent or solutionKnowing the concentration of solutes is important in controlling the stoichiometry of reactant for reactions that occur in solutionA concentrated solution contains a large amount of solute in a given amount of solution. A 10 mol/L solution would be called concentrated.A dilute solution contains a small amount of solute in a given amount of solution. A 0.01 mol/L solution would be called dilute.Add water (hydrate) to diluteremove water (evaporate by boiling) to concentrate
11Concentrations Qualitative (words): -Concentrated -dilute Quantitative (numbers):-percent by mass-percent by volume-Molarity (M)-molality (m)
12What is the [solid solute] in a liquid solvent. What part What is the [solid solute] in a liquid solvent? What part? Out of what whole?Read the above as: What is the concentration of solid solute in a liquid solvent?
13Percent by Mass Mass of Solvent? Mass of solution = Percent by mass = mass of solute x mass of solutionUse when combining a solid solute into a liquid solventMass of solution =mass of solute + mass of solventMass of Solvent?
14Finding Mass of Solvent Or finding the mass of a volume. Is there a relationship b/w mass and volume? -- Density or D -- D = m/V or m = DV Since our solvent is H2O and we know that the DH2O = 1.0 g/ml (constant) So, m = DV or m = (1.0 g/ml) (V)
15Example Percent by Mass: To maintain a sodium chloride (NaCl) concentration similar to ocean water, an aquarium must contain 3.6 g NaCl per g of water. What is the percent by mass of NaCl in the solution?Equation:Percent by mass = mass of solute x mass of solutionGiven:Mass of solute: 3.6 g NaClMass of solvent: g H2O= g NaCl x 1003.6 g NaCl g H2O= %
16What is the percent by mass of NaHCO3 in a solution containing 20 What is the percent by mass of NaHCO3 in a solution containing 20.0 g of NaHCO3 dissolved in mL of H2O?
17But what if the solute and solvent are both liquids?
19Percent by Volumevolume of solute Percent by volume = x 100 volume of solution
20Try Calculating Percent by Volume: What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 155 mL of water?Percent by volume = volume of solute x 100volume of solution
21How much isopropyl alcohol is actually in a 473 mL solution of 99 % isopropyl alcohol? Percent by volume = volume of solute x 100volume of solution
22Molarity The unit M is read, “molar” Molarity (M) = moles of solute Liters of solutionThe unit M is read, “molar”
23Calculating Molarity: What is the molarity of an aqueous solution containing 0.22 mol of glucose (C6H12O6) in 1.5 L of solution?
24A 100. 5 mL solution contains 5. 10 g of glucose (C6H12O6) A mL solution contains 5.10 g of glucose (C6H12O6). What is the molarity of this solution? (The molar mass of glucose is g/mol.)
25Remember, Molarity is just a measure of how concentrated a solution is (or how “strong” it is)… so,Which is the most concentrated solution?a) M CuSO4b) 1.75 M CuSO4c) 3.00 M CuSO4d) 7.00 M CuSO4
26Which is the least concentrated solution? a) M HClb) 0.75 M HClc) 2.00 M HCld) 4.25 M HCl
27We know from Guy Lussac’s Law that V of a solution changes with T. This change in V alters the M of the solution.We also know that mass does not change with T.So, sometimes it is more useful to describe solutions in terms of how many moles of solute are dissolved in a specific mass of solvent.
28Molality Molality (m) = moles of solute kg of solvent You LOVE me!! The unit m is read, “molal”
29Calculating Molality: In the lab, a student adds 4.5 g of sodium chloride (NaCl) to 0.1 kg of water. Calculate the molality.
30What is the molality of a solution containing 10 What is the molality of a solution containing 10.0 g of Na2SO4 dissolved in g of water?
31In the lab, you might use concentrated solutions of standard molarities, called stock solutions. But, you can prepare a less-concentrated solution by diluting the stock solution with additional solvent.
32Making a Dilute Solution removesamplemoles ofsoluteinitial solutionsame number ofmoles of solutein a larger volumemixMaking a Dilute Solutiondiluted solution
33DilutionPreparation of a desired solution by adding water to a concentrate.Moles of solute remain the same.M = Molarity (Concentration), V = volume
34M1V1 = M2V2 Dilution Equation: M1 and V1 represent the molarity and volume of the stock solution, while M2 and V2 represent the molarity and volume of the dilute solution.
35So for instance, what volume, in mL, of a 2 So for instance, what volume, in mL, of a 2.00M calcium chloride (CaCl2) stock solution would you use to make 0.50 mL of 0.300M calcium chloride solution?
36What volume of a 3. 00M KI stock solution would you use to make 0 What volume of a 3.00M KI stock solution would you use to make L of a 1.25M KI solution?
37Concentration “The amount of solute in a solution” A. % mass = mass of solutemass of sol’nB. % volume = V of soluteV of sol’nC. molarity (M) = moles of soluteL of sol’n– used most often in this class% by mass – medicated creams% by volume – rubbing alcoholMOLARITY - Most common unit of concentrationMost useful for calculations involving the stoichiometry of reactions in solutionMolarity of a solution is the number of moles of solute present in exactly 1 L of solution:moles of solutemolarity = liters of solutionUnits of molarity — moles per liter of solution (mol/L),abbreviated as MRelationship among volume, molarity, and moles is expressed asVL M Mol/L = L (mol) = moles(L)There are several different ways to quantitatively describe the concentration of a solution, which is the amount of solute in a given quantity of solution.1. Molarity– Useful way to describe solution concentrations for reactions that are carried out in solution or for titrations– Molarity is the number of moles of solute divided by the volume of the solutionMolarity = moles of solute = mol/Lliter of solution– Volume of a solution depends on its density, which is a function of temperature2. Molality– Concentration of a solution can also be described by its molality (m), the number of moles of solute per kilogram of solvent– Molality = moles of solutekilogram solvent– Depends on the masses of the solute and solvent, which are independent of temperature– Used in determining how colligative properties vary with solute concentrations3. Mole fraction– Used to describe gas concentrations and to determine the vapor pressures of mixtures of similar liquids– Mole fraction () = moles of componenttotal moles in the solution– Depends on only the masses of the solute and solvent and is temperature independent4. Mass percentage (%)– The ratio of the mass of the solute to the total mass of the solution– Result can be expressed as mass percentage, parts per million (ppm), or parts per billion (ppb)mass percentage = mass of solute 100%mass of solutionparts per million (ppm) = mass of solute 106parts per billion (ppb) = mass of solute 109– Parts per million (ppm) and parts per billion (ppb) are used to describe concentrations of highly dilute solutions, and these measurements correspond to milligrams (mg) and micrograms (g) of solute per kilogram of solution, respectively– Mass percentage and parts per million or billion can express the concentrations of substances even if their molecular mass is unknown because these are simply different ways of expressing the ratios of the mass of a solute to the mass of the solutionM =molLD. molality (m) = moles of solutekg of solventE. M1V1 = M2V dilutions