Lab Report: Make sure your report includes the data and observations from your experiment, calculations of molar mass and a brief discussion of possible sources of error. Also include the answers to the following questions: 1. Explain the effect of each of the following errors upon your calculated molar mass. Be specific as to whether the result would be high or low and explain why. a. Some solvent is lost by evaporation. b. Some of the unknown is lost during transfer to the test tube. c. The thermometer consistently reads one degree too low. d. Part of the solute does not dissolve. 2. Is it necessary that the solvent be absolutely pure? Explain your answer clearly. 3. Many ionic compounds, e.g., NaCl, are strong electrolytes and dissociate completely upon dissolution in water. Explain clearly the effect upon the freezing point when a 1.00 m solution of NaCl in water is made (calculate the freezing point). Hint: What is the van't Hoff i-factor for this solute?

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T. The solublity of ones fn re and decreasing pressuure (1) increasing pressure and increasing temperature (3) decreasing temperature and increasing pressure (2) ally decreases with increasing temperature and decreasing pressure (4) decreasing temperature and decreasing pressure. 8. When a nonvolatile solute s uch as ammonium sulfate is dissolved in a solvent like water, one of the (1) a decrease in the boiling point of the liquid (2) an increase in the vapor (4) a decrease in the observed effects is pressure of the solvent freezing point of the liquid (3) an increase in the vapor pressure of the solute . In which of the following solvents would you expect kBr to be most soluble? (1) CClu (carbon tetrachloride) 0. Calculate the mass percent of HOCH-CH2OH in a solution made by dissolving 6.4 g of HOCHCH20H in 11. During osmosis (1) pure solutes diffuse through a membrane but solvent does not (2) pure solvent (2) CHsCH2OH (ethanol) (3) CaHe (benzene (4) CoH14 (hexane) 48.2 g of water. (1)13.3% (2) 6.9% (3) 7.4% (4) 11.7% diffuses through a membrane but solutes do not (3) pure solvent and a solution both diffuse at the same time through a membrane (4) gases diffuse through a membrane into a solution and build up pressure 12. Which of the following gases is expected to have a highest solubility in water? (1) HCI (2) N2 (3) CH (4) O2 13. How many grams of water are needed to dissolve 27.8 g of ammonium nitrate NH NOs in order to prepare a (1)0.157 g (2) 769 g (3) 36.2 9 0.452 m solution? The molar mass of NH4NOs is 80.04 g/mol. (4) 57.0 g (1) enough solvent to make 14. To make a 3.0 m solution, one could take 3.00 moles of solute and add L of solution (2) enough solvent to make 1.00 kg of solution (3) 1.00 L of solvent (2) 1.00 kg of solvent 15. What volume of 2.00 M CHOH solution is needed to provide 0.500 mol of CHJOH? (1)3,.12 mL (2) 10.0 mL (3) 167 mL (4) 250 mL 16. Assuming 100% dissociation, which ofthe follow ng compounds is listed correctly with its van't Hoff factor? (4) Ala(SO4), i-5 (2) NH4N03, i#3 (3) Sucrose, i:0 (1) NaS0+/-2 17. Calculate the van't Hoff factor of NasPO in a 0.40 m solution whose freezing point is -2.6C. 15 pts]

Experiment 10 Colligative Properties Introduction A pinch of wa make boiling water hotter. A handful will clear the snow from your steps. Every day we the physical properties of materials around us, but often don't know why we use these particular s or what chemistry is involved. Modifying the temperature of phase changes, by adding a second chemical to the pure solvent are examples of manipulating the Colligative Properties of a solution. this lab, we will study how varying the concentration and type of a salt affects the point of a solution. Colligative properties are properties of a solution containing 2 or more components. Typically, the primary is the solvent and the other called the such as color or hardness, properties depend on the number of particles of astute in the not the identity of the In many cases, the rokute will determine the number of solute particles (degree of ionization, solubility, etc,) in the solvent, but a colligative property does not depend upon the nature of the particles. Two colligative properties commonly encountered are boiling point elevation and freezing point depression (the temperature of of a is lower than of pure solvent). We will be studying boiling point elevation in this Most of the previous work that you have done with solutions has involved units of molarity, M, or moles of solute per liter of solution. Boiling point elevation calculations (as well as those for freezing point depression) or moles of solute per kilogram of solvent. boili change of temperature. When the temperature of a solution changes, the volume of the solution also changes. Since molarity depends on a change in wil the solution's molarity. Molality depends on the mass of the solvent. and thus is independent of temperature. n't Hoff Factor salt into and the of moles inorganic salts in an aque the based on the addition of the number dissociates, the total number of particles in the solution will be of cations and anions produced from the dissociation. Thus; Nacion Na Choaa (2moles of particles) Cacbrs Ca +2ch (3moles of particles) The quantity of particles produced per mole of solute is called the van'tHoff factor and is given the symbol, i, If 1 mole of sodium chloride were completely dissociated, iwould be 2. This theory works very well for dilute solutions and non-electrolytes (i 1, no dissociation at all since nonelectrolytes not ionize), For does not always apply to more concentrated solutions. Thus, when there are a large number of particles in a solution, they have a tendency to recombine as the salt and you don't get 100% dissociation. example, at a NaCl concentration of 0.1M, iwill be 1.81 (90% dissociation) rather than 2 (100%). Boiling Point Elevation solute causes the solution to boil at a higher When a solution is heated, the presence of a non-volatile point of the pure liquid and the temperature than the pure The difference between the boiling boiling point of the solution is: 169

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