1 Lecture 7: Solutions Solutions Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 2 Solutions: Solute and Solvent Solutions Are homogeneous mixtures of two or more substances. Consist of a solvent and one or more solutes. Solutes Spread evenly throughout the solution. Cannot be separated by filtration. Can be separated by evaporation. Are not visible, but can give a color to the solution. 3 Identify the solute in each of the following solutions: A. 2 g sugar and 100 mL water B mL of ethyl alcohol and 30.0 mL of methyl alcohol C mL water and 1.5 g NaCl D. Air: 200 mL O 2 and 800 mL N 2 Learning Check 4 Water Is the most common solvent. Is a polar molecule. Forms hydrogen bonds between the hydrogen atom in one molecule and the oxygen atom in a different water molecule. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 5 Formation of a Solution Na + and Cl - ions On the surface of a NaCl crystal are attracted to polar water molecules. Are hydrated in solution with many H 2 O molecules surrounding each ion. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 6 When NaCl(s) dissolves in water, the reaction can be written as H 2 O NaCl(s) Na + (aq) + Cl - (aq) solid separation of ions Equations for Solution Formation 7 Solid LiCl is added to water. It dissolves because A. The Li + ions are attracted to the 1) oxygen atom ( - ) of water. 2) hydrogen atom ( + ) of water. B. The Cl - ions are attracted to the 1) oxygen atom ( - ) of water. 2) hydrogen atom ( + ) of water. Learning Check 8 Two substances form a solution when there is an attraction between the particles of the solute and solvent. A polar solute is soluble in polar solvent; a nonpolar solute is soluble in nonpolar solvent Like dissolves like Ionic solutes, such as NaCl, dissolve in water, a polar molecule; polar molecules will dissolve in water Oil, a nonpolar solute, will not dissolve in water, but will dissolve in nonpolar solvent Like Dissolves Like 9 Solvents Solutes Water (polar) Ni(NO 3 ) 2 CH 2 Cl 2 (nonpolar) (polar) I 2 (nonpolar) 10 Which of the following solutes will dissolve in water? Why? 1) Na 2 SO 4 2) gasoline (nonpolar) 3) I 2 4) HCl Learning Check 11 Electrolytes and Nonelectrolytes Lecture 7: Solutions Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 12 In aqueous solution, Strong electrolytes produce ions and conduct an electric current (they are completely ionized). Weak electrolytes produce a few ions (slightly ionized). Nonelectrolytes do not produce ions. Solutes and Ionic Charge Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 13 Complete each of the following equations for strong electrolytes in water: H 2 O A. CaCl 2 (s) 1) CaCl 2 (s) 2) Ca 2+ (aq) + Cl 2 (aq) 3) Ca 2+ (aq) + 2Cl (aq) H 2 O B. K 3 PO 4 (s) 1) 3K + (aq) + PO 4 3 (aq) 2) K 3 PO 4 (s) 3) K 3 + (aq) + P 3 (aq) + O 4 (aq) Learning Check 14 Equivalents An equivalent (Eq) is the amount of an electrolyte or an ion that provides 1 mole of electrical charge (+ or -) 1 mole Na + = 1 equivalent 1 mole Cl = 1 equivalent 1 mole Ca 2+ = 2 equivalents 1 mole Fe 3+ = 3 equivalents 15 Electrolytes in IV Solutions Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings Table 8.6 16 Learning Check A. In 1 mole of Fe 3+, there are 1) 1 Eq2) 2 Eq 3) 3 Eq B. In 2.5 mole SO 4 2, there are 1) 2.5 Eq2) 5.0 Eq 3) 1.0 Eq 17 Solubility is The maximum amount of solute that dissolves in a specific amount of solvent. Expressed as grams of solute in 100 grams of solvent, usually water. g of solute 100 g water Saturated solutions Contain the maximum amount of solute that can dissolve. Have undissolved solute at the bottom of the container. Unsaturated solutions Contain less than the maximum amount of solute. Can dissolve more solute. Lecture 7: Solubility 18 At 40 C, the solubility of KBr is 80 g/100 g H 2 O. Identify the following solutions as either (S) saturated or (U) unsaturated. Explain. A. 60 g KBr added to 100 g of water at 40 C. B. 200 g KBr added to 200 g of water at 40 C. C. 25 g KBr added to 50 g of water at 40 C. Learning Check 19 Effect of Temperature on Solubility Solubility Depends on temperature. Of most solids increases as temperature increases. Of gases decreases as temperature increases. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 20 Soluble and Insoluble Salts Ionic compounds that Dissolve in water are soluble salts. Do not dissolve in water are insoluble salts. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 21 Solubility Rules Soluble salts Typically contain at least one ion from Groups 1A(1) or NO 3 , or C 2 H 3 O 2 (acetate). Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings TABLE 8.7 22 Using the Solubility Rules The solubility rules help predict whether a salt is soluble or insoluble in water. TABLE 8.8 Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 23 Use the solubility rules to determine if each salt is (S) soluble or (I) insoluble. A. ______ Na 2 SO 4 B. ______ MgCO 3 C. ______ PbCl 2 D. ______ MgCl 2 Learning Check 24 Formation of a Solid When solutions of salts are mixed, A solid forms if ions of an insoluble salt are present. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 25 Equations for Forming Solids A molecular equation shows the formulas of the compounds. Pb(NO 3 )(aq) + 2NaCl(aq) PbCl 2 (s) + 2NaNO 3 (aq) An ionic equation shows the ions of the compounds. Pb 2+ (aq) + 2NO 3 (aq) + 2Na + (aq) + 2Cl (aq) PbCl 2 (s) + 2Na + (aq) + 2NO 3 (aq) A net ionic equation shows only the ions that form a solid. Pb 2+ (aq) + 2Cl (aq) PbCl 2 (s) 26 Learning Check Write the formula of an insoluble salt. If any, and the net ionic equation for each of the following mixtures: A. BaCl 2 (aq) + Na 2 SO 4 (aq) B. AgNO 3 (aq) + KCl(aq) C.KNO 3 (aq) + NaC(aq) 27 Lecture 7:Solutions Percent Concentration Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 28 The concentration of a solution: relationship between the amount of solute (g or mL) and the amount (g or mL) of solution. A mass percent (%m/m): ratio of the mass of the solute to the mass of the solution times 100 Mass percent can also be expressed as a mass/volume ration or volume/volume ratio Percent Concentration 29 Mass of Solution 8.00 g KCl g KCl solution Add water to give g solution Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 30 The calculation of mass percent (%m/m) requires the Grams of solute (g KCl) and Grams of solution (g KCl solution). g of KCl = 8.00 g g of solvent (water) = g g of KCl solution = g 8.00 g KCl (solute) x 100 = 16.0% (m/m) g KCl solution Calculating Mass Percent 31 A solution is prepared by mixing 15.0 g Na 2 CO 3 and 235 g of H 2 O. Calculate the mass percent (%m/m) of the solution. 1) 15.0% (m/m) Na 2 CO 3 2) 6.38% (m/m) Na 2 CO 3 3) 6.00% (m/m) Na 2 CO 3 Learning Check 32 1.(m/m) How many grams of NaCl are needed to prepare 225 g of a 10.0% (m/m) NaCl solution? 2.(m/v) How many mL of a 4.20%(m/v) will contain 3.15 g KCl? 3.(v/v) How many grams of NaOH are needed to prepare 125 mL of a 8.80%(m/v) NaOH solution? Using Percent Concentration Factors 33 How many grams of NaOH are needed to prepare 75.0 g of 14.0%(m/m) NaOH solution? 1)10.5 g NaOH 2) 75.0 g NaOH 3)536 g NaOH Learning Check 34 How many milliliters of a 5.75 % (v/v) ethanol solution can be prepared from 2.25 mL ethanol? 1) 2.56 mL 2) 12.9 mL 3) 39.1 mL Learning Check 35 Lecture 7: Molarity (M) and Dilutions Molarity (M) Is a concentration term for solutions. Gives the moles of solute in 1 L solution. = moles of solute liter of solution 36 What is the molarity of L NaOH solution if it contains 6.00 g NaOH? Calculation of Molarity 37 What is the molarity of 325 mL of a solution containing 46.8 g of NaHCO 3 ? 1) M 2) 1.44 M 3) 1.71 M Learning Check 38 Calculations Using Molarity How many grams of KCl are needed to prepare 125 mL of a M KCl solution? 39 How many grams of AlCl 3 are needed to prepare 125 mL of a M solution? 1) 20.0 g AlCl 3 2) 16.7g AlCl 3 3) 2.50 g AlCl 3 Learning Check 40 Dilution Dilution: the process of mixing a solution with solvent to obtain a lower concentration In a dilution: water is added, volume increases, concentration decreases. Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 41 Initial and Diluted Solutions In the initial and diluted solution, The moles of solute are the same. The concentrations and volumes are related by the following equations: For percent concentration C 1 V 1 = C 2 V 2 initial diluted For molarity M 1 V 1 = M 2 V 2 initial diluted 42 Dilution Calculations with Percent What volume of a 2.00 %(m/v) HCl solution can be prepared by diluting 25.0 mL of 14.0%(m/v) HCl solution? Prepare a table: C 1 = 14.0 %(m/v)V 1 = 25.0 mL C 2 = 2.00%(m/v)V 2 = ? Solve dilution equation for unknown and enter values: C 1 V 1 = C 2 V 2 V 2 = V 1 C 1 = (25.0 mL)(14.0%) = 175 mL C % 43 Learning Check What is the percent (%m/v) of a solution prepared by diluting 10.0 mL of 9.00% NaOH to 60.0 mL? 44 Dilution Calculations What is the molarity (M) of a solution prepared by diluting 0.180L of M HNO 3 to L? Prepare a table: M 1 = MV 1 = L M 2 = ?V 2 = L Solve dilution equation for unknown and enter values: M 1 V 1 = M 2 V 2 M 2 = M 1 V 1 = (0.600 M)(0.180 L) = M V L 45 Learning Check What is the final volume (mL) of 15.0 mL of a 1.80 M KOH diluted to give a M solution? 1) 27.0 mL 2) 60.0 mL 3) 90.0 mL 46 Molarity in Chemical Reactions In a chemical reaction, The volume and molarity of a solution are used to determine the moles of a reactant or product. molarity ( mole ) x volume (L) = moles 1 L If molarity (mole/L) and moles are given, the volume (L) can be determined moles x 1 L = volume (L) moles 47 Using Molarity of Reactants How many mL of 3.00 M HCl are needed to completely react with 4.85 g CaCO 3 ? 2HCl(aq) + CaCO 3 (s) CaCl 2 (aq) + CO 2 (g) + H 2 O(l) 48 Learning Check How many mL of a M Na 2 S solution are needed to completely react 18.5 mL of M NiCl 2 solution? NiCl 2 (aq) + Na 2 S(aq) NiS(s) + 2NaCl(aq) 1) 4.16 mL 2) 6.24 mL 3) 27.8 mL 49 Learning Check If 22.8 mL of M MgCl 2 is needed to completely react 15.0 mL of AgNO 3 solution, what is the molarity of the AgNO 3 solution? MgCl 2 (aq) + 2AgNO 3 (aq) 2AgCl(s) + Mg(NO 3 ) 2 (aq) 1) M 2) M 3) M 50 Learning Check How many liters of H 2 gas at STP are produced when Zn react with 125 mL of 6.00 M HCl? Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g) 1) 4.20 L H 2 2) 8.40 L H 2 3) 16.8 L H 2 51 Lecture 7:Solutions Properties of Solutions Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings 52 Solution vs. Colloid vs. Suspension TABLE 8.12 53 Learning Check A mixture that has solute particles that do not settle out, but are too large to pass through a semipermeable membrane is called a 1) solution 2) colloid 3) suspension 54 Osmosis In osmosis, water (solvent) flows from the lower solute concentration into the higher solute concentration. The level of the solution with the higher concentration rises. The concentrations of the two solutions become equal with time. Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 55 Osmosis A semipermeable membrane separates a 4% starch solution from a 10% starch solution. Starch is a colloid and cannot pass through the membrane, but water can. What happens? semipermeable membrane 10% starch4% starch H2OH2O 56 Water flow Equalizes The 10% starch solution is diluted by the flow of water out of the 4% and its volume increases. The 4% solution loses water and its volume decreases. Eventually, the water flow between the two becomes equal. 7% starch H2OH2O 57 Osmotic Pressure Osmotic pressure is Produced by the solute particles dissolved in a solution. Equal to the pressure that would prevent the flow of additional water into the more concentrated solution. Greater as the number of dissolved particles in the solution increases. 58 Learning Check A semipermeable membrane separates a 10% starch solution (A) from a 5% starch solution (B). If starch is a colloid, fill in the blanks in the statements below. 1. Solution ____ has the greater osmotic pressure. 2. Water initially flows from ___ into ___. 3. The level of solution ____will be lower. 59 Osmotic Pressure of the Blood Red blood cells Have cell walls that are semipermeable membranes. Maintain an osmotic pressure that cannot change or damage occurs. Must maintain an equal flow of water between the red blood cell and its surrounding environment. 60 Isotonic Solutions An isotonic solution Exerts the same osmotic pressure as red blood cells. Is known as a physiological solution. Of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells. Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 61 Hypotonic Solutions A hypotonic solution Has a lower osmotic pressure than red blood cells. Has a lower concentration than physiological solutions. Causes water to flow into red blood cells. Causes hemolysis: RBCs swell and may burst. Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 62 Hypertonic Solutions A hypertonic solution Has a higher osmotic pressure than RBCs. Has a higher concentration than physiological solutions. Causes water to flow out of RBCs. Causes crenation: RBCs shrinks in size. Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 63 Dialysis In dialysis, Solvent and small solute particles pass through an artificial membrane. Large particles are retained inside. Waste particles such as urea from blood are removed using hemodialysis (artificial kidney). Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings 64 Learning Check Each of the following mixtures is placed in a dialyzing bag and immersed in pure water. Which substance, if any, will be found in the water outside the bag? A. 10% KCl solution B. 5% starch solution C. 5% NaCl and 5% starch solutions