Solutions- Chapter 12 & 13 Academic Chemistry

Transcription

1 Objectives: Solutions- Chapter 12 & 13 Academic Chemistry Describe the unique role of water in chemical and biological systems Develop and use general rules regarding solubility through investigations with aqueous solutions Calculate the concentration of solutions in units of molarity Use molarity to calculate the dilutions of solutions Distinguish between types of solutions such as electrolytes and nonelectrolytes and unsaturated, saturated, and supersaturated solutions Investigate factors that influence solubility such as temperature, through an essential lab Vocabulary: 1. Solution 2. Solute 3. Solvent 4. Colloid 5. Suspension 6. Tyndall effect 7. Soluble 8. Insoluble 9. Precipitate 10. Miscible 11. Immiscible 12. Solvation 13. Solubility 14. Unsaturated 15. Saturated 16. Supersaturated 17. Dilute 18. Concentrated Provided: Henry s Law: S1 = S2 P1 P2 % by mass = mass solute x 100 mass solution Molarity (M) = mol M 1 V 1 = M 2 V 2 L Periodic Table, Polyatomic Ions List, Solubility Rules, Solubility Graphs, Calculator CHECKLIST: How to be successful in OTHS Academic Chemistry Pay attention and take notes in class Ask questions in class on material that is not clear Work every page in the practice packet for the unit Check answers to the practice packet online at Come to tutorials with any chemistry teacher Do the online homework and check solutions once they become available Always do the practice test for every test & ask good questions on review day Keep up with the calendar for the class/be aware of approaching quizzes, tests, & other deadlines Use videos posted on website as a quick and convenient tutorial Read the chapter in the book pg1 pg2 pg3 pg4 pg5 pg6 pg7 pg8 pg9

2 Name Period Solutions Vocabulary Cross-Word Puzzle (Use your foldable as a word bank) 1

3 Practice Solubility Behavior 1. For each action, write whether it would increase (I), decrease (D), or have no effect (N), on the solubility of the solid solute. a. Decreasing the temperature of the solution b. Decreasing the pressure over the solution 2. For each action, write whether it would increase (I), decrease (D), or have no effect (N), on the solubility of the gaseous solute. a. Placing a soda in the refrigerator b. Increasing the temperature of the solution c. Decreasing the pressure around the solution 3. For each action, write whether it would increase (I), decrease (D), or have no effect (N), on the RATE of solubility of the solute. a. Using a packet of sugar instead of a sugar cube b. Heating up a sugar and tea solution c. Stirring a solid solute into a solution of water 4. Pressure only affects the solubility of. HENRY S LAW The solubility of O2 gas in water is 2.54 g/l at 1.79 atm pressure. What is the solubility if the pressure is decreased to atm? 2. The solubility of N2 gas in water is 0.35 g/l at 2.5 atm pressure. What is the pressure if the solubility increases to 0.48 g/l? 2

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5 Solubility Curves Worksheet #2 Use the solubility curves below to answer the questions 1. Which substance is probably a gas? Why? 2. Which substance has the highest solubility at 20 o C? 3. Which substance is least soluble at 40 o C? 4. The solubility of which salt is least affected by temperature? 5. At 70 o C, how much ammonium chloride can be dissolved in 100 g water? 6. At 70 o C, how much ammonium chloride can be dissolved in 500 g water? 7. At 90 o C, how much ammonia can be dissolved in 200 g water? 8. At 80 o C, 40 g of potassium chloride is dissolved in 100 g water. Is the solution unsaturated, saturated, or supersaturated? 9. At 30 o C, 13 g of potassium chlorate (KClO3) is dissolved in 100 g water. Is the solution unsaturated, saturated, or supersaturated? 10. At 20 o C, 145 g of potassium iodide is dissolved in 100 g water. Is the solution unsaturated, saturated, or supersaturated? 11. A saturated solution of ammonium chloride is made with 100 g water at 90 o C. How much ammonium chloride would crystallize out if the solution is cooled to 50 o C? 4

6 Solution Concentration Worksheet #1 Solutions are composed of a solute (what gets dissolved) and a solvent (what does the dissolving). In chemistry we need to be able to express quantitatively exactly how much solute is dissolved in a given amount of solution. This quantitative description is known as the solution s concentration. You will learn two units for expressing solution concentration. I. Percent by Mass % by mass = mass solute x 100 mass solution* * solution = solute + solvent Sample Problems: 1. What is the % by mass of NaHCO 3 in a solution containing 20.0 g NaHCO 3 (solute) dissolved in 600. ml water (solvent)? The density of water is 1.0 g/ml (so 1.0 g = 1.0 ml). Mass of water = 600 g, % by mass = 20.0 g x 100 = 3.23 % (20.0 g g) 2. You have g of an aqueous bleach (NaClO) solution. The percent by mass of the solute (NaClO) is 3.62%. How many grams of NaClO are in the solution? Do a proportion: 3.62 = x _ x = 54.3 g NaClO (solute) 3. Refer to #2. How many grams of solvent (water in this case, because it is an aqueous solution) are present in this solution? How many ml is this? You know the total mass of solution is g. Practice Problems: g = solute + solvent g = 54.3 g + x x = g water (solvent) = ml water (the density of water is 1 g/ml) 1. What is the % by mass of a sucrose solution containing 50.0 g sucrose in 500. ml water? 2. What is the % by mass of an iodine solution containing 2.0 g iodine (solute) in 200. g alcohol (solvent)? 3. How many grams of KCl are present in g of an aqueous solution that is 20.0% KCl by mass? 4. Refer to #3. How many grams of solvent (water) are present in this solution? 5. What is the mass of a solution that contains 25.0 g fructose and is 10.0% fructose by mass? KEY: % % g g g 5

7 II. Molarity Molarity = moles solute mol/l is abbreviated M Liters solution Sample Problems: 1. What is the molarity of a solution containing 0.50 mol glucose in 2.0 L solution? Molarity = 0.50 mol = 0.25 mol/l = 0.25 M glucose 2.0 L 2. What is the molarity of a solution containing 40.0 g NaCl in 700. ml of solution? First change grams of solute to moles using molar mass: 40.0 g NaCl = mol NaCl Also change ml of solution to L (1 L = 1000 ml): 700. ml = L Molarity = mol = M L 3. How many moles of KI are dissolved in 3.00 L of a M solution? How many grams of KI? M = mol/l mol = M x L mol = (0.125 M) x (3.00 L) = mol KI Then change moles to grams using molar mass: mol KI = 62.3 g KI Practice Problems: Calculate the molarity of each of the following: mol of HCl in 1.0 L of solution mol of HNO 3 in 4.0 L of solution mol of NH 4Cl in 50.0 ml of solution g of NaCl in ml of solution g of Cr(NO 3) 3 in 325 ml of solution Find the number of moles AND the number of grams of solute required for each of the following: L of 3.00 M NH 4Cl ml of M NaF L of 3.0 M NaOH KEY: M M M M M mol, 161 g mol, 5.25 g mol, 330 g 6

8 Helpful formulas: Practice Worksheet #2: Solution Concentration Units Mass % = mass solute x 100 Molarity (M) = moles solute mass solution L solution 1. You have 350 g of an aqueous bleach solution. The percent by mass of the solute (NaClO) is 2.5 %. How many grams of NaClO are in the solution? 2. What is the % by mass of C 6H 12O 6 (glucose) in a solution containing 20.0 g glucose dissolved in 180 g water? 3. (a) What is the molarity of a solution containing 1.5 mol NaF in a 1.5 L solution? (b) What is the molarity of a solution containing 50.0 g NaF in a 800 ml solution? 4. How many grams of NaNO 3 are dissolved in 2.0 L of a 0.50 M solution? 5. What is the total solution volume if the concentration is 2.0 M and the amount of dissolved KCl is 25.0 g? 7

9 Dilutions Worksheet 1) If I dilute ml of 0.10 M lithium acetate solution to a volume of ml, what will the concentration of this solution be? 2) If I have ml of a 0.50 M NaBr solution, what will the concentration be if I add ml more water to it? 3) If I leave ml of 0.50 M sodium chloride solution uncovered on a windowsill and ml of the solvent (water) evaporates, what will the new concentration of the sodium chloride solution be? 4) I have an acid solution that is 12 M HCl. How many milliliters of this solution do I need to make ml of 3.8 M HCl? 5) In #4, how much water needs to go with the 12 M acid to give the total volume of ml? 6) A 2.5 L sample of a solution of sea water has a NaCl concentration of 5.4 M. What is the new concentration of this solution if it is boiled down to a volume of 1.0 L? 8

10 Practice Worksheet: Solubility Rules and Precipitation Reactions #1-8: Indicate whether the following compounds are soluble (aq) or insoluble (s): Pb(NO3)2 LiOH CuSO4 HgBr2 AgC2H3O2 PbSO4 Cu3(PO4)2 NH4Cl # 9-14: (a) predict the products of the DR reaction and be sure to check your formulas! (b) balance the equation (c) use solubility rules to determine (aq)--soluble or (s)--insoluble for each compound 9. NH4Cl + Pb(NO3)2 10. NaOH + FeSO4 11. BaI2 + CuSO4 12. Hg(C2H3O2)2 + Na2S 13. CaBr2 + Li3PO4 14. MgCl2 + K2CO3 9