Chemistry Assessment: #3 Part 1 Solubility and Colligative Properties

Transcription

1 Name: Date: Period: Chemistry Assessment: #3 Part 1 Solubility and Colligative Properties PG 2 Vocabulary PG 3 Reading Guide PG 4 True or False PG 5 & 6 Molarity PG 7 & 8 Concentration Phet PG 9 & 10 Saturated & Unsaturated Solutions POGIL PG 11 & 12 POGIL Cont. PG 13 & 14 Solubility Curve Practice PG 15 & 16 More Solubility Curve PG 17 Molality PG 18 More Molality PG 19 Colligative Properties PG 20 Colligative Properties PG 21 Freezing Point Elevation PG 22 Boiling Point Depression PG 23 & 24 Solutions & Colligative Properties 1

2 Outcome 4 Part 1 Vocabulary 1. aqueous solution 2. solute 3. solvent 4. concentration 5. molarity (M) 6. colligative property 7. freezing-point depression 8. boiling-point elevation 9. saturated solution 10. unsaturated solution 11. supersaturated solution 2

3 Solutions Worksheet Answer each of the following questions using your notes and Section 16.1 in your textbook. (pp ) 1. Define solvent. 2. Define solute. 3. How do you tell the difference between a solute and a solvent in a solution? 4. What is an aqueous solution. 5. Define solubility. 6. What is a saturated solution? 7. What is a supersaturated solution? 8. Sugar in water is an example of which solute-solvent combination? a. liquid liquid b. gas - liquid c. solid liquid d. liquid solid 9. Compare substances that are soluble and insoluble in water and give an example of each. 10. When you dissolve salt in water how do you identify what is the solute and what is the solvent? 11. Give two examples of a solid - liquid, solute solvent combination. 12. Pewter is mixture of tin and copper. If the mixture was 80% tin and 20% copper how do you know which the solvent is and which is the solute? 13. Hard water is a mixture of minerals and water. How do you know which is the solvent and which is the solute? 14. Identify the substance known as the universal solvent and explain why is has that description. 15. List three things you can do to make a solute dissolve faster in a solvent? 3

4 TRUE or FALSE? (If FALSE rewrite the statement to make it true.) 16. Adding more solute makes a solute dissolve faster. 17. Cooling a solution makes a solute dissolve faster. 18. Stirring a solution make a solute dissolve faster. 19. In a BaCl2 (aq) solution, water is the solute and BaCl2 (aq) is the solvent. 20. The temperature of the solvent does not affect the solubility of a solute in a solvent. 21. The surface area of the solute does not affect the solubility of a solute in a solvent. 22. Stirring a solution does not affect the solubility of a solute in a solvent. 23. In an aqueous solution of some substance water is always the solute. 24. In a sample of pewter consisting of 85% tin and 15% copper, copper is the solvent and tin is the solute. 25. In a sample of pewter consisting of 95% tin and 5% copper, tin is the solvent and copper is the solute. 26. In hard water, minerals are the solvent and water is the solute. 27. Salt in water is an example of a solid - liquid solute - solvent combination. 28. Mixing a small amount of copper with tin is an example of a solid-solid solute solvent combination. 29. Dissolving carbon dioxide in water is an example of a gas liquid solute solvent combination. 4

5 Molarity of Solutions Worksheet Molarity (M) = moles of solute moles x grams = grams liters of solution moles 1. What mass of the following chemicals is needed to make the solutions indicated? a. 1.0 liter of a 1.0 M mercury (II) chloride (HgCl 2) solution b. 2.0 liters of a 1.5 M sodium nitrate (NaNO 3) solution c. 5.0 liters of a 0.1 M Ca(OH) 2 solution d. 100 ml of a 0.5 M (NH 4) 3PO 4 solution 2. Calculate the molarity of the following solutions. a. 12 g of lithium hydroxide (LiOH) in 1.0 L of solution b. 198 g of barium bromide (BaBr 2) in 2.0 L of solution c. 54 g of calcium sulfide (CaS) in 3.0 L of solution 3. Calculate the volume of each solution, in liters. a. a 1.0 M solution containing 85 g of silver nitrate (AgNO 3) b. a 0.5 M solution containing 250 g of manganese (II) chloride (MnCl 2) c. a 0.4 M solution containing 290 g of aluminum nitrate (Al(NO 3) 3) 4. How many grams of potassium chloride (KCl) are required to make 2.0 L of a 3.0 M solution? 5

6 5. How many grams of magnesium chloride (MgCl 2) are needed to make 6.0 L of a 3.0 M solution? 6. What mass of barium chloride (BaCl 2) is needed to make 0.5 L of a 4.0 M solution? 7. What mass of iron (II) sulfate (FeSO 4) is needed to make 200 ml of a 0.25 M solution? 8. What is the molarity of a solution in which 1.6 g of sodium hydroxide (NaOH) are dissolved in 125 ml of solution? 9. What is the molarity of a solution in which 5.0 g of sodium carbonate (Na 2CO 3) are dissolved in 200 ml of solution? 10. How many grams of silver nitrate (AgNO 3) are needed to make 2.0 L of a 0.10 M solution? L of a solution contain 25 g of potassium permanganate (KMnO 4). What is the molarity of the solution? 12. How many grams of glycerine (C 3H 8O 3) are needed to make 100 ml of a 2.5 M solution? 13. What is the molarity of a solution containing 150 g of zinc sulfate (ZnSO 4) per liter? 14. A test tube contains 10 ml of a 3.0 M CaCO 3 solution. Calculate the number of grams of CaCO 3 in the tube. 6

7 Name Date Period Concentration PhET Weblab Pre-Lab: use your textbook or google to define the following terms : 1. Saturated 2. Supersaturated 3. Unsaturated4. Solubility 5. Concentration 6. Solute 7. Solvent 8. Solution 9. Molarity 10. Dilute Part 1: Concentration Calculations Using Molarity Formula - Procedure: 1. For Trial 1: Fill up the tank to 1 L, choose Solute: Drink Mix(solid), drag purple concentration meter into the tank as shown: 2. Shake the shaker to add solute to the water until you have an approx. concentration = 2 mol/l. Record the exact Concentration of Soln in Data Table Reduce the volume of water to approx L by draining half the tank. Without recording anything, notice any effect on the concentration and answer Question Click to begin next trial. 5. For Trial 2(etc), Choose Cobalt (II) Nitrate (solid) & record its chemical formula and molar mass in Data Table 1. Fill your tank to the 9 th mark as shown. Note the tank s volume is graduated by 0.1 L marks, so the volumes are written to the hundredths decimal place. Again, add solute until your concentration is approx. 2.0 mol/l and record the exact concentration in your table. If the solution reaches saturation before you are able to reach this concentration, write the word SATURATED in the concentration column and mark through the rest of that row on the Analysis Table We will discuss saturation in Part 2. Click trial 6. Repeat #5 for the other solid solutes, each time use 0.1 L less water (one mark down) to begin next Part 1-Analysis: 1. For the unsaturated trials only, use the molarity formula: to find the moles of solute added in each trial, fill in Analysis Table 1. Note the unit for Molarity is mol/l, but is often called Molar, abbreviated with a capital M. Show work for Cobalt(II) Nitrate only below: 7

8 2. For the unsaturated trials only, convert the mole of solute to grams for each trial and fill in Analysis Table 1. Recall: 1 mol = Molar Mass(g). Show work for Cobalt (II) Nitrate only below: Part 1-Data&Analysis Solute Chemical Formula DATA TABLE 1 ANALYSIS TABLE 1 Volume Concentration Moles of Molar Mass Grams of of Water of Soln Solute (g/mol) Solute (g) (L) (mol/l or M) (mol) UNKNOWN UNKNOWN 1.00 OMIT UNKNOWN Part 1-Questions: Explain using complete sentences. 1. Without adding any new solute, did draining some solution dilute the solution? 2. Which solute required the most mass to reach the 2 mol/l concentration? Least mass? 3. Which solutes saturated before reaching a concentration of 2 mol/l? 4. As you completed the trials, why should it take less & less mass to reach the concentration of 2.0 mol/l? 8

9 Saturated and Unsaturated Solutions -Is there a limit to the amount of solute that will dissolve in a solvent? Why? We use solutions every day. People who wear contact lenses use lens solution to rinse their contacts and keep them wet. Athletes who consume sports drinks after exercising benefit from the electrolytes in those solutions. This activity will explore whether or not there is a limit to how much of one substance can dissolve. Model 1 Saturated and Unsaturated Solutions 1. Which illustration below represents a. solute particles in a solid state in water? b. solute particles in an aqueous state? 9

10 2. What variables are controlled in all five beakers of Model 1? 3. Count the particles present in each beaker of Model 1. Fill in the table to show the number of dissolved solute particles and the number of solid solute particles. 4. Consider the beakers in Model 1. a. Which beakers represent unsaturated solutions? b. Which beakers represent saturated solutions? 5. Beakers A E in Model 1 are depicted as representing five different or separate solutions. They could also be considered as five snapshots of the same beaker over time. In other words, if additional measured quantities of solute were stirred into beaker A in small increments over time, then beakers B E would result. a. When a small amount of additional solute is added to an unsaturated solution, what happens to the number of dissolved particles? Provide specific evidence from Model 1 to support your answer. b. When a small amount of additional solute is added to a saturated solution, what happens to the number of dissolved particles? Provide specific evidence from Model 1 to support your answer. c. Predict what would happen if a small amount of additional solute were stirred into beaker E in Model 6. Have each person in your group provide an example of the word saturated as it is used in an everyday context. Summarize the meaning of the word in the space below. 7. Use a grammatically correct sentence to explain why beakers D and E in Model 1 are labeled as saturated. Be sure to incorporate the words solute and solvent in your explanation, and reach a consensus within your group. 8. What feature in the beakers in Model 1 would typically enable a student to distinguish a saturated solution from an unsaturated one simply by looking at the beaker? 10

11 9. Beaker C in Model 1 is shown as saturated. Explain why this is the correct category for beaker C even though the typical feature listed in Question 8 is not present. 10. If you were handed a beaker containing a clear solution (with no solid solute at the bottom), and asked to identify it as saturated or unsaturated, what simple test could you perform to determine the answer. Model 2 Solute Dissolved vs. Solute Added The following data refer to an experiment in which a measured mass of solid is added to 10.0 g of 20 C water. The mixture is stirred and allowed to sit for 3 hours. Ten separate trials are conducted for the experiment. 11. Four of the trials in Model 2 correspond to beakers A, B, D, and E from Model 1. Write the letters for those beakers next to the corresponding trial numbers in Model Identify the following variables in the experiment in Model 2. Dependent variable Independent variable Controlled variable(s) 13. Sketch a graph of the data for the experiment in Model 2. A space has been provided next to the data table. Be sure to consider which variable belongs on each axis. 14. Consider the data in Model 2. a. Which trials represent solutions that are unsaturated? b. Which trial numbers represent solutions that are saturated? 11

12 c. Describe the feature in the graph that can help you identify the saturated solutions. Explain. 15. Which trials in the experiment in Model 2 would have visible amounts of solid on the bottom of the beaker? 16. For Trial 8 in Model 2, determine the mass of solid solute remaining on the bottom of the beaker. Show your calculation. 17. Imagine that the contents of the beaker for Trial 8 in Model 2 are vigorously stirred and then poured into filter paper in a funnel. a. Is the liquid that drips from the filter (the filtrate) unsaturated or saturated? Explain. b. Which beaker in Model 1 best represents the filtrate that would be obtained? Extension Questions 18. Predict what would happen to the mass of solid solute sitting on the bottom of the beaker in Trial 8 in Model 2 when the following changes occur. Use complete sentences to support your predictions. a. More water is added to the beaker. b. The beaker is heated (assume no evaporation occurs). c. The beaker is allowed to sit uncovered for two days and some water evaporates. 12

13 Solubility - How is the quantity of solute in a saturated solution determined? Why?When we add salt to a pot of boiling water or sugar to a pitcher of iced tea, we expect that the added solute will completely dissolve. It requires a large quantity of these solutes to saturate a solution. On the other hand, water has flowed over rock riverbeds for centuries and only dissolved enough material in some cases to provide a trace of certain minerals in the water. Different solutes, such as salt, sugar, or minerals, dissolve to very different extents in water (and other solvents). In this activity you will learn how to quantify the amount of solute that is dissolved in a saturated solution. Model 1 Three Solutions The following data refer to three experiments in which the same solute is added to water in a beaker at 20 ºC. The mixtures are stirred and then allowed to sit for three hours before measuring the amount of solid that dissolves. Ten separate trials are conducted for each experiment. 1. Identify the variable(s) that were controlled among all three experiments in Model What variable(s) were changed purposefully among the three experiments in Model 1? 3. What experimental question can be answered by analyzing the data in the three experiments in Model 1? Use the words solvent and solute in your question. 4. In each of the three experiments in Model 1, determine the point in the experiment that the beakers became saturated. Draw a box around the entire section of data in each experiment that represents saturated solutions. 13

14 5. Consider the data in Model 1. a. Which experiment shows the largest mass of dissolved solute in the saturated solutions? b. Propose an explanation for why the mass of dissolved solute changed among the three experiments. Read This! Solubility is a measure of the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature. In other words, it is the ratio of solute to solvent in a saturated solution at a specific temperature. Solubility is typically reported as grams of solute per 100 g H2O. For example, if a maximum of 20.4 g of table sugar (sucrose) will dissolve in 10.0 g of water at 20 C, then the solubility of sucrose would be 204 g sucrose/100 g H2O. 6. Would it be acceptable for a student to use Trial 2 from Experiment 1 to determine the solubility of the solute in Model 1? Explain your group s answer in a complete sentence. 7. In Model 1 none of the experiments used 100 g of water. Use complete sentences to explain how the ratio grams of solute per 100 g H2O can be calculated from the data given in Model Use the data in Model 1 to calculate the solubility of the solute (at 20 ºC) for all three experiments. Show your work. Experiment 1: Experiment 2: Experiment 3: 9. Circle the word or phrase that best completes each of the statements below. a. When the volume of solvent increases, the mass of solute that can dissolve in a saturated solution (increases/decreases/stays the same). b. When the volume of solvent increases, the solubility of a solute at a given temperature (increases/decreases/stays the same). 10. A student claims, In Experiment 3, Trial 9, 18.0 grams of solute dissolves, whereas in Experiment 1, Trial 9, only 3.6 grams of solute dissolves. Obviously, the solubility is greater in Experiment 3. With your group, devise a well-constructed response. 14

15 11. Calculate the mass of the solute used in Model 1 that is needed to make a saturated solution in g of water without leaving any solid solute at the bottom. Show your work. Adapted from POGIL Activities for High School Chemistry by Sarah Eder Solubility Curve Practice Problems Directions: Find the mass of solute will dissolve in 100mL of water at the following temperatures? 1. KNO3 at 70 C = 2. NaCl at 100 C= 3. NH4Cl at 90 C= 4. Which of the above three substances is most soluble in water at 15 C. = 2. Solution Saturated or Unsaturated? If unsaturated: How much more solute can dissolve in the solution? a solution that contains 70g of NaNO 3 at 30 C (in 100 ml H 2O) a solution that contains 50g of NH 4Cl at 50 C (in 100 ml H 2O) a solution that contains 20g of KClO 3 at 50 C (in 100 ml H 2O) a solution that contains 70g of KI at 0 C (in 100 ml H 2O) 3. a. What is the solubility of KCl at 5 C? b. What is the solubility of KCl at 25 C? 15

16 c. What is the solubility of Ce2(SO4)3 at 10 C? d. What is the solubility of Ce2(SO4)3 at 50 C? 4. At 90 C, you dissolved 10 g of KCl in 100. g of water. Is this solution saturated or unsaturated? 5. A mass of 100 g of NaNO3 is dissolved in 100 g of water at 80ºC. a) Is the solution saturated or unsaturated? b) As the solution is cooled, at what temperature should solid first appear in the solution? Explain. 6. Use the graph to answer the following two questions: Which compound is most soluble at 20 ºC? Which is the least soluble at 40 ºC? 7. Which substance on the graph is least soluble at 10 C? 8. A mass of 80 g of KNO3 is dissolved in 100 g of water at 50 ºC. The solution is heated to 70ºC. How many more grams of potassium nitrate must be added to make the solution saturated? Explain your reasoning Part II Graphing Questions 1. Graph the following data the graph Your graph must: -Be neat and organized (use a ruler) -X and Y axis must have proper scale -Have properly labeled axes -Use a different color for the two different solubility curves. Sodium Chloride Solubility Temperature Solubility (g of solute/100 ml of H 20) At 50 0 C, 35 grams of sodium chloride and 50 grams of copper sulfate are dissolved into 100 ml of water, a. Which solution was saturated? Which was unsaturated? Explain. b. How much more solute could you add to the unsaturated solution? Copper Sulfate Solubility Temperature Solubility (g of solute/100 ml of H 20) 16

17 Molality Worksheet Complete the following questions and problems relating to molality. 1. Write the equation for molality: 2. Write the equation for molarity: 3. Explain in words how molality and molarity differ. 4. What is the molality of a solution in which 0.32 moles AlCl3 has been dissolved in 2,200 g water? 0.15m 5. What mass of water is needed to prepare a 1.20 molal solution using 0.60 mol propyleneglycol? 0.500kg H2O 6. What is the molality of a solution in which mol CO2 (molar mass = g/mol) is dissolved in 591 g water? 0.25m 7. What is the molality of a solution in which 13.7 g NaCl has been dissolved in 500.0g water? 8. How many grams of ethanol, C2H6O (molar mass g/mol), are need to prepare a 0.10 molal solution using kg water. 0.47m 9. What is the molality of a solution that contains 63.0 g HNO3 in kg H2O? 4.61g 17

18 10. What is the molality of a solution that contains mol HC2H3O2 in kg H2O? 11. What mass of water is required to dissolve 100. g NaCl to prepare a 1.50 m solution? 12. What mass of water must be used to dissolve kg C2H5OH to prepare a 3.00 m solution? 13. What mass of H2SO4 must be dissolved to 2.40 kg H2O to produce a 1.20 m solution? 14. What is the number of molecules of C2H5OH in a 3 m solution that contains 4.00 kg H2O? 15. What is the molality of a solution that contains 80.0 g Al2(SO4)3 in 625 g H2O? 16. What mass of water is required to dissolve 175 g KNO3 to produce a 2.25 m solution? 17. What mass of HC2H3O2 must be dissolved in 800. g H2O to produce a 6.25 m solution? 18. How many moles of NH4 + ions are dissolved in kg of H2O if the concentration of (NH4)3PO4 is m? 19. What is the molality of a saturated solution of NaNO3 at 20 o C? (use the solubility graph on PG 13) 20. What is the molality of a saturated solution of NH4Cl at 70 o C? (use the solubility graph on PG 13) 18

19 1. What is a colligative property? Colligative Properties Questions 2. What are three examples of colligative properties? 3. How does adding a solute affect the boiling point of a solvent? 4. How does adding a solute affect the freezing point of a substance? 5. What is osmotic pressure? 6. What is the Van t Hoff Factor? 7. Which salt, NaCl or CaCl2, has a greater effect on freezing point? Explain. 8. What is the equation for determining the a. Boiling Point Elevation b. Freezing Point Depression c. Osmotic Pressure 9. A solution is prepared by dissolving 27.0 g of urea [(NH2)2CO], in g of water. Calculate the boiling point of the solution. Urea is a non-electrolyte. kb=0.51 ( C kg)/mol. 10. What mass of glycerin (C3H8O3), a nonelectrolyte, must be dissolved in g of water to give a solution with a freezing point of C? 19

20 Consider the following solutions for #13 & #14 a m Na3PO4 in water b m CaBr2 in water. c m KCl in water d m HF in water (HF is a weak acid) 11. Assuming complete dissociation of soluble salts, which solution(s) would have the same boiling point as m C6H12O6 in water? (non-polar electrolyte). 12. Which solution would have the largest freezing point depression? Consider the following solutions for #13 & #14 chose one of the following: a. pure water b. solution of C6H12O6 (χ = 0.01) in water c. solution of NaCl (χ = 0.01) in water d. solution of CaCl2 (χ = 0.01) in water 13. Highest freezing point 14. Lowest freezing point 15. Highest Boiling Point 16. Lowest Boiling Point 17. Highest Osmotic Pressure 18. A solution of glucose (MM = g/mole) in 500. g of water had an initial boiling point of o C. a. What is the molality of the solution? b. How many moles of glucose were added? c. How many grams of glucose were added? 20

21 Chemistry: Colligative Properties Freezing Point Depression 1. How much will the freezing point be lowered if enough sugar is dissolved in water to make a 0.50 molal solution? 2. What is the freezing point of a solution of a nonelectrolyte dissolved in water if the concentration of the solution is 0.24 m? 3. What is the freezing point of a solution that contains 68.4 g of sucrose, C12H22O11, dissolved in 1.00x10 2 g of water? 4. Suppose that 98.0 g of a nonelectrolyte is dissolved in 1.00 kg of water. The freezing point of this solution is found to be o C. What is the molecular mass of the solute? 5. A researcher places 53.2 g of an unknown nonelectrolyte in 505 g napthalene. The nonelectrolyte lowers napthalene s freezing point by 8.8 o C. What is the molar mass of the unknown substance? ANSWERS: o C o C o C amu g/mol 21

22 Chemistry: Colligative Properties Boiling Point Elevation 1. The boiling point of carbon tetrachloride is 76.8 o C. A given solution contains 8.10 g of a nonvolatile electrolyte in 300 g of CCl4. It boils at 78.4 o C. What is the gram molecular mass of the solute if the boiling point constant for CCl4 is 5.03 C/m? 2. The molal boiling point constant for ethyl alcohol is 1.22 o C/molal. Its boiling point is 78.4 o C. A solution of 14.2 g of a nonvolatile nonelectrolyte in 264 g of the alcohol boils at 79.8 o C. What is the gram molecular mass of the solute? 3. Calculate the mass of a mole of a compound that raises the boiling point of water to o C at kpa when 51 g of the compound is dissolved in 500 g of water. 4. Suppose that 13 g of a nonelectrolyte is dissolved in 0.50 kg of benzene. The boiling point of this solution is o C. What is the molecular mass of the solute? ANSWERS: g/mol g/mol g/mol amu 22

23 SOLUTIONS AND COLLIGATIVE PROPERTIES SET A: 1. Find the molarity of all ions in a solution that contains moles of aluminum chloride in 820. ml solution. Answer: [Al 3+]= M, (Cl-] = 0.603M. 2. Find the molarity of each ion present after mixing 27 ml of 0.25 M HNO3 with 36 ml of 0.42 M Ca(NO3)2 (Note: There is no reaction taking place.) Answer: [H+]= 0.11 M, [NO3-]= 0.59M, [Ca2+]= 0.24 M. 3. Find the molarity of each ion present after mixing 35 ml of 0.42 M K2SO4 with 27 ml of 0.17M K3PO4. Answer: [K +] = 0.71 M, [SO42-]= 0.24 M, [PO4 3-]= M. 4. The freezing point of a glucose solution (C6H12O6; molar mass= g/mole) is C. The density of the solution is 1.50 g/ml. What is the molarity of the glucose solution? (Kf for water is 1.86 C.kg/mole) Answer: 4.16 mole/l 5. What is the normal boiling point of a 2.70 M solution of KBr that has a density of 1.80 g/ml?(kb for H2O is C.kg/mole) Answer=: C 6. A solution contains 15 grams of sucrose, C12H22O11, in 250 grams of water. What is the freezing point of the solution? (determine the molality first) 7. What is the boiling point of the solution in problem #6 above? 8. Calculate the boiling point and freezing point of a solution that contains 30.0 grams of acetic acid, HC2H3O2, dissolved in 250 grams of water. 9. Calculate the freezing point of a solution containing 5.70 grams of sugar, C12 H22O11, in 50 grams of water. 23

24 10. Calculate the boiling point of the sugar solution in problem 18 above. 11. Calculate the freezing point of a solution containing 60. grams of NaOH in 500 grams of water. 12. Calculate the boiling point of the solution in the above problem. 13. How many grams of ethanol, CH3OH, must be dissolved in 500 grams of water to lower the freezing point to -6.51oC? 24