Solutions: Solubility, Intermolecular Forces - Chemistry PDF

Solutions I – Solubility and Percent Concentration (Reading Section 14.3, 15.1, 15.2, 15.3) Part 1 Intermolecular Forces (Section 14.3) Part 2 Solubility Part 3 Solution Concentration Expressions Part 4 Mass Percent Part 5 Volume Percent  Review – Polar vs. Non-polar Mole...

Solutions I – Solubility and Percent Concentration (Reading Section 14.3, 15.1, 15.2, 15.3) Part 1 Intermolecular Forces (Section 14.3) Part 2 Solubility Part 3 Solution Concentration Expressions Part 4 Mass Percent Part 5 Volume Percent  Review – Polar vs. Non-polar Molecules Water is a polar CCl4 is a non- molecule because polar molecule its has dipole because it does moment. not have dipole moment. 2  Polarity and Solubility affe affe Dipole moment  molecular polarity  ct ct affe Intermolecular force  Solubility and boling point ct Intermolecular Forces (IMFs) are the attractive forces that hold 2 or more molecules together. (This is the reason why molecules “stick” together.) 3  Part 1 Intermolecular Forces (IMFs) 4  Objectives IMFs exists between the molecules of same substance (e.g. between two water molecules). Its strength is reflected on the boiling point of a substance. (Discuss briefly.) IMFs exists between the molecules of different substances (e.g. between sugar and water molecules). Its characteristics is reflected on its solubility (solute and solvent). (Our focus.) 5  IMFs and Boling Point The stronger the intermolecular forces, the higher the boiling point of a substance. 6  Intermolecular Forces (IMFs) – Chapter 14.3 Types: 1. Ionic Force - attractive force between ions. 2. Dipole-Dipole Force – attractive force between the opposite charged ends of polar molecules. 3. Hydrogen Bond – dipole-dipole force between the H atom and highly electronegative atom (N, O, F). 4. London Dispersion Forces (aka van de Waals force) – attractive force between non- polar molecules due to the temporary induced dipole-dipole force and is the weakest IMF. 7 1) Ionic Force in Ionic Compounds Attractive forces between the cation (positively charged) and anion (negatively charged) particles. 8 2) Dipole-Dipole Force in Polar Molecules Attractive forces between the positive end of one polar molecule and the negative end of another polar molecule. 9  3) Hydrogen Bonding (e.g. water molecules) A kind of dipole-dipole force Unusually strong attractions Hydrogen is bonded to a highly electronegativity atom (N, O or F). The small size anions (N, O or F) make the IMFs exceptionally strong. 10  Hydrogen Bonding Two factors account for the extraordinary strong strength in H bond: 1. great polarity of the bond (i.e. large ∆EN) 2. close approach of the dipole due to the small size of hydrogen and anions. 11 Hydrogen Bond in Different Types of Molecules ···· hydrogen 12 bond  4) London Dispersion Forces in Non-polar Molecules Due to the temporary distortion of electron density Larger size atom or molecule has stronger London forces (i.e. easy to distort) Weakest IMFs Iodine molecule (I2) – nonpolar covalent bond 13  London Dispersion Forces in Halogen Elements Z = 17 Cl2 Z Br2 = 35 Z I2 = 53 The bigger the atomic size, the greater the electron cloud distortion the stronger the London Dispersion 14 15  Application: Significances of H Bond i n Water Water exists as liquid form in room temperature Life forms on earth can survive because of this water property. 16 Water is in liquid form at room temperature Because of the high boiling point of water, we can have liquid water to use. 17  Part 2 Solubility – Molecular View “Like dissolves Li ke” 18  Review – What is solution? – homogeneous mixture (uniform composition in every part of the mixture) – Three types: 1. Gaseous solution e.g. air (consists of O2, N2, etc.) 2. Solid solution (aka. alloy) e.g. brass (consists of copper and zinc) 3. Liquid solution (we focus on this type) e.g. rubbing alcohol (consists of ethanol and water) 19  Concept Check Which one(s) is/are not solution? a)apple juice b)distilled water c)wine d)liquid nitrogen 20  Solute vs. Solvent (solid/gas + liquid) Solvent – substance that dissolves the solute to make solution water as solvent -- forms aqueous solution e.g. salt solution organic solvent e.g. acetone e.g. nail polish Solutes – substances creates a solution when dissolved in a solvent (usually lesser amount – apply for solid solute) – name of solute is usually used to name the solution e.g. sugar solution 21 Miscible vs. Immiscible (liquid + liquid) Two liquids that completely dissolve in each other are miscible liquids. Two liquids that are not miscible in each other are immiscible liquids. Polar water and nonpolar oil are immiscible liquids and do not mix to form a solution. 22  Terminology Regardless the physical state of substance: We use “soluble” to cover the situation when two substances form a solution. We use “insoluble” to cover the situation when two substances cannot form a solution. This helps to simplify the consideration. 23 Use IMFs to understand Solution Formation Types of Solution: 1. Ionic salts (solute) in polar solvent (e.g. water) Ionic-Dipole Force - attraction between ions (solute) and charged ends of polar solvent molecules. 2. Polar solute in polar solvent (e.g. water) Dipole-Dipole Force – attraction between the opposite charged ends of polar solute and solvent molecules. 24 Use IMFs to understand Solution Formation (cont.) Types of Solution: 3. Nonpolar solute in nonpolar solvent (e.g. oil or CCl4) London Dispersion Forces – attraction due to the temporary induced dipole-dipole force of nonpolar solute and solvent molecules. Ionic and polar substances do NOT mix with nonpolar substances. No solution is formed. 25 1) Example of Ionic-Dipole Force: NaCl solution 26 2) Example of Dipole-Dipole Force : Sugar Solution Sugar and water molecules are polar. The δ+ and δ- centres of water molecules attract with the δ+ and δ- centres of sugar molecule. This interaction pulls the sugar crystals into the water.  Another Look – Sugar molecules dissolving in Water Sugar Molecule  Application: Water as Universal Solvent Nutrients and waste (ionic or polar compounds) can be transported by blood which is made up of water. polar ionic compounds compounds Salt (NaCl) Glucos e Bone Uric Ca5(PO4)3(OH) Acid  “Like Dissolve Like” Concept 1. Ionic + Polar  Solution 2. Polar + Polar  Solution 2. Nonpolar + Nonpolar  Solution 3. Polar + Nonpolar  Do NOT form solution Example: Nonpolar oil molecules do not interact with polar water molecule. Two separate layers resulted. 30 Exercise A – Identify the Types of IMFs As Pure Ionic/ IMFs Substanc Polar/ e Nonpolar compound a) NaOH b) CCl4 c) NH3 d) CH2Cl2  Exercise B – Mix with solvent water Apply “Like dissolve Like” concept. Solute Forming solution with water? Yes/No a) NaOH b) CCl4 c) NH3 d) CH2Cl2 32 Water and CCl4 33 I2 in CCl4 and Water 34 Sugar in CCl4 and Water 35  IMFs and Solubility - Summary If IMF exists between solute and solvent molecules, they mix well. Solution is formed. If IMF does NOT exist between solute and solvent molecules, they do NOT mix. No solution is formed. 36  Concept Check Which of the following solutes will generally not dissolve in the specified solvent? Choose the best answer. (Assume all of the compounds are in the liquid state.) a) CCl4 mixed with water (H2O) b) NH3 mixed with water (H2O) c) N2 mixed with methane (CH4) Copyright © Cengage Learning. All rights reserved 37  How come? Why oil and water do not mix? We see sugar or salt crystals disappear when they are mixed with water. Why? We are told that we should not take vitamin A without doctor’s recommendation. Why? 38  Part 3 Solution Concentration Expressions 39  Solution Concentration Expressions Tells us how much solute is dissolved in a given quantity of solution/solvent. Qualitative expression – “diluted solution” vs. “concentrated solution” “saturated” vs. “unsaturated” Quantitative expressions – - molarity (M) - mass percent (% w/w) - volume percent (% v/v) - mass/volume percent (% w/v) - parts per million (ppm) 40  Saturated vs. Unsaturated Solution The solubility of a substance (solute) in a solvent has a limit. This limit is temperature dependent. Saturated solution – contains as much solute as will dissolve at that temperature. Unsaturated solution – the limit of solute that will dissolve at that temperature has not been reached (i.e. the solvent can hold more solute). 41  Qualitative Expression of Concentration A relatively small amount of solute dissolved in a dilute solution. A relatively large amount of solute dissolved in a 42  Read this statement: “The solubility of sugar in water at 20 degrees Celsius is 204 grams in 100 cc. of water. ” The followings are a must components for a solubility expression: 1. Solute - sugar 2. Solvent - water 3. Temperature – 20 oC 4. Amount of solute – 204 g 5. Amount of solvent – 100 c.c. 43  179 g/100 g 487 g/100 g water water at 0 oC at 100 oC 44  Concept Check 1 Read this statement: “The solubility of sugar in water at 20 degrees Celsius is 204 grams in 100 cc. of water. ” Question: Which one is dilute solution? a. 200 g sugar in 100 cc. water b. 12 g sugar in 100 cc. water 45  Concept Check 2 Read this statement: “The solubility of sugar in water at 20 degrees Celsius is 204 grams in 100 cc. of water. ” Question: Which one(s) is/are unsaturated solution? a. 200 g sugar in 100 cc. water b. 12 g sugar in 100 cc. water c. all of above d. none of above 46  Dilute vs. Unsaturated Dilute – relative description (depending on other solutions) Unsaturated – comparing to the solubility of the solute in a solvent at particular temperature Both dilute or concentrated solution can be unsaturated solution.  Significant Figures Exercise (Review) Example Report the number in 3 significant figures: a) 0.0108 b) 0.0050060 48  Metric Unit Volume units: 1 L = 1000 mL Mass units: 1 kg = 1000 g = 1 x 103 g 1 g = 1000 mg = 1 x 103 mg 49  Exercise – Identify Solute and Solution Generally, solute name is used to name the solution. e.g. salt solution – salt is the solute Substance Solute or Solution? liquid acetic acid acetic acid acetic acid solution isopropyl alcohol liquid isopropyl alcohol isopropyl alcohol solution  Part 4 Mass Percent (% m/m) or (% w/w) 51 Mass Percent (% w/w) or (% m/m) aka “percent-by-mass” General formula is as follows: For example, Any mass unit (e.g. kg, lb…etc) can be used but must be consistent for both solute 52  Example 1 – Find Mass Percent (% w/w) A 135-g sample of seawater is evaporated to dryness, leaving 4.73 g of solid residue. Calculate the mass percent of solute present in the original seawater. Answer Mass of solute = 4.73 g Mass of solution = 135 g Percent-by-mass = (mass of solute/mass of solution) x 100% = w/w 53 Example 2 – Find Mass Percent (% w/w) What is the percent-by-mass concentration of glucose in a solution made by dissolving 5.5 g of glucose in 78.2 g of water? Answer Mass of solute = 5.5 g Mass of solution = mass of solute + mass of solvent = 5.5 g of glucose + 78.2 g of water = 83.7 g Percent-by-mass = 54  Exercise 1 – Find Mass Percent (% w/w) What is the percent-by-mass concentration of salt solution made by dissolving 10.5 g of NaCl in 200.0 g of water? Answer: 4.99% w/w 55  Exercise - Writing the Mass Percent as Fraction Mass Percent Fraction 0.9% by mass salt solution 1.25% (w/w) NaOH solution 56  Example 3 (a) – Find mass of solute or solvent from given mass Cow’s milk containspercent 4.5% by mass of lactose C12H22O11. Calculate the mass of lactose present in 175 g of milk. Answer – use ratio and proportion approach Mass of solute = ? g Mass of solution = 175 g Percent-by-mass = 4.5% 57  Example 3 (b) – Find mass of solute or solvent from given mass Cow’s milk containspercent 4.5% by mass of lactose C12H22O11. Calculate the mass of lactose present in 175 g of milk. Answer – use percent formula approach Mass of solute = ? g Mass of solution = 175 g Percent-by-mass = 4.5% 58 Exercise 2 – Find mass of solute or solvent from given mass percent Formalin solution contains 40% by mass of formaldehyde chemical. Calculate the mass of formaldehyde present in 50 g of formalin solution. Answer: 20 g formaldehyde Exercise 3 - Find mass of solute or solvent from given mass percent What mass of water must be added to 425 g of pure formaldehyde to prepare a 40%(by mass) formalin solution. [Hint: Mass of water = mass of solution – mass of solute] Answer: 638 g 60  Part 5 Volume Percent (% v/v) 61  Percent by Volume (% v/v) Useful when the solute and solvent are both liquids. Volume unit for both solute and solvent must be the same. For example, Vinegar - 5 % v/v of acetic acid = 5 mL of liquid acetic acid mixed with water, to a total volume of 100 mL. 62  Example 1 – Finding % (v/v) A hand sanitizer solution is prepared by mixing 33 mL pure isopropyl alcohol with water to make 50 mL solution. What is the percent (v/v) of the alcohol in solution? Answer %(v/v) = 33 mL alcohol____ x 100% 50 mL solution = 66.0 % (v/v) hand sanitizer solution 63  Exercise 1 – Finding % (v/v) A hand sanitizer solution is prepared by mixing 40 mL pure isopropyl alcohol with water to make 50 mL solution. What is the percent (v/v) of the alcohol in solution? Answer: 80% (v/v) 64  Example 2 – Finding Solute Amount A medication contains 20 %(v/v) liquid drug. If 40 mL of the medication has been administered to the patient, what is the amount of drug the patient has received? Answer 65  Exercise 2 – Finding Solute Amount A solution medication must be made such that for every 5 parts solution, there is one part liquid drug. a) what is the percent by volume for this drug? b) If the total solution volume is to be 400 mL, how Answer: 20% much liquid drug is needed? (v/v) Answer: 80 mL of liquid drug  Example 3 – Finding Solution Amount A medication contains 20 %(v/v) liquid drug. A patient needs to receive 10 mL of the drug, how many mL of the medication should be administered? Answer Solution amount = 67 Exercise 3 – Finding Solution Amount A medication contains 9.8 %(v/v) liquid drug. A patient needs to receive 4.5 mL of the drug, how many mL of the medication should be administered? Answer: 45.9 mL 68  Part 6 Mass by Volume Percent (% m/v) or (% w/v) 69 Percent Mass by Volume (% w/v) or (% m/v) Useful when solute is a solid and solvent is a liquid. For example, normal saline (NS) - 0.90% w/v of NaCl = 0.9 grams of NaCl dissolved in water, to a total volume of 100 mL solution. 70  Comparable Units for Solute and Solution in Percent Calculation In solution, it is common to measure the solution in volume (e.g. L or mL etc.) while the solute is measured in mass (e.g. g or mg etc). The calculation of Percent Mass by volume is based on the following fact: For pure water at room temperature, approximate, 1 gram = 1 mL  Density of water Hence, “gram” and “mL” are equivalent (or matching) units for this percent calculation. 71  Example 1 – Find % (w/v) An IV solution is prepared by dissolving 25 g glucose (C6H12O6) in water to make 500 mL solution. What is the percent (w/v) of the glucose in the IV solution? Answer %(m/v) = 25 g glucose____ x 100% 500 mL solution = 5.0 %(w/v) glucose solution LecturePLUS Timberlake 72  Exercise 1 – Find % (w/v) A saline solution is made by dissolve 10 g NaCl in water to make 1 litre solution. What is the percent (w/v) of the saline solution? Answer: 1 % w/v 73  Example 2 – Find Solution Volume How many mL of 5 % (w/v) glucose solution are given if a patient receives 200 g of glucose? Answer where V is the solution volume 74  Exercise 2 – Find Solution Volume How many mL of 5 % (w/v) glucose solution are given if a patient receives 150 g of glucose? Answer: 3000 mL LecturePLUS Timberlake 75  Example 3 – Find Solute Amount If a patient received 1.5 L of 5 % (w/v) glucose solution, how many grams of glucose was transferred to the patient? Answer 76  Exercise 3 – Find Solute Amount If a patient received 800 mL of 5 % (w/v) glucose solution, how many grams of glucose was transferred to the patient? Answer: 40 g 77 Mass by Volume Percent can be more than 100 For example: A 100%mL coffee has 150 grams sugar. What is the mass by volume percent concentration of sugar in coffee? Answer - It is because mass and volume are two different types of measurement. - For concentrations of percent by mass or percent by volume, it must be less than 100 %. 78  Summary for Percent Concentrations Mass Percent (% w/w or % m/m) - Consistent unit for both solute and solution. Volume Percent (% v/v) - Consistent unit for both solute and solution. Mass by Volume Percent (% w/v) or (% m/v) - Units used are g for solute and mL for solution. 79