CHEM 1332 Study Guide - Final Guide: Labatt Brewing Company, Molar Mass, Boiling Point

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11 Aug 2020

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Labatt a. to#rgpenies:scolllgative only on the solute concentration property : physical property that depend at = tsoiv - tsolution dtf = i ktm. *knowthis : mm = #kf du freezing : subtract ( tdf ) ( mass solvent : kg ) boiling : add. It thermometer reads a different temp : no effect on molar mass. Freezing point of electrolyte ( t vhf) so if will i be more significant. * a solution has a lower freezing temperature than a pure solvent ; the more concentrated a solution becomes the lower thefreezing point. O *dated (cid:12200) crystallizes pamgoieutgrie rated as it freezes cooling down over time ask. mu#ifaetteenwsucgnnttoma/&eyosmiifm:gie ine3 n. Lower freezing pt than pure subst . t. at#i4ikinetics-n-uolkrxh:. ralereauton:- concentration of a product or reactant with respectto time. Iz t starch blue 1 black complex ionic strength s % % ennmafa *dan rate constant in .

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Please help me solve for the molar mass of sample 1 and 2 and the molecular formula

Experiment 1084-03: Determination of M.M. by Freezing Point Depres sion Measure the freezing-point depressions solute whose empirical formula is known Pool the class hat occur with solutions containing mass of the solute and its Background Information However, as soon as the solution begins to freeze, Adding a solute to a pure, non-volatile lquid ature will remain constant untl all the (solvent) lowers the vapor pressure of the solvent raises its boiling point, and lowers (depresses) its freezing point. The extent to which these are aftected depends on the relative number of solute particlos in the solution. Properties of solutions that depend only on the number of solute molecules in a given quantity of solvent are called colligative properties. Such cyclohexane turns into solid. Once the substance again. The freezing point is the temperature where it stays constant, Le. the liquld phase and the sold phase of the cyclohexane coexists (Figure 3-1) boiling point elevation and osmotic pressure. They do NOT dopend on the nature of the solute, but DO depend on the nature of the solvent. As a consequence, colligative properties can be used to determine an unknown molar mass for a solute. In this experiment, we will be using cyclohexane (d " 0.779 gmL, K, . 20.5 oC/m) as the solvent to determine the molar mass of a white solid with an empirical formula of C,HC. The freezing point depression, Î7, is the difference between the freezing point of the pure solvent, TP, and the freezing point of the solution (solvent and solute). T As mentioned above, thits quantity is proportional only to the molal concentration of the solute, m Figure 3-1. Cooling Curves The proportionality constant, K, is called the freezing-point-depression constant. The K value of 20.5 C/m for Cyclohexane is one of the largest values one can find. Molal concentration is defined as the number of moles of substance in 1 kg of solvent. Now we can calculate the molar mass of a solute from ATã K,, the mass of the The freezing point of a solution in cyclohexane can be obtained in a similar way. Cooling results in an initial rapid decrease in the temperature until freezing begins as seen in the cooling curve of the pure solvent. However, the temperature of the solution does not remain constant while being frozen. As the cyclohexane in the solution treezes, cyclohexane is taken away from the solution and the concentration of the solute becomes higher In the liquid portion. Thus the molal concentration of the solute increases and the freezing point of the solute and the mass of the solvent. remaining liquid becomes lower. The result is a steadily decreasing freezing temperature until the solution is completely frozen. When all the solution In order to determine ATP, we will measure the freezing point of pure cyclohexane and the freezing point of a solution of the solute in is frozen, the temperature decreases more rapidly To evaluate the freezing point of pure cyclohexame, you will cool a sample of this substance, and measure the temperature as a The freezing point of the solution is the temperature at which the solution starts to freeze. portion represents the concentration of the starting function of time. As cooling begins, theOnly at this point, the concentration of the liquid temperature of the cyclohexane decreases rapidly.

DETERMINATION oF MOLAR EXPERIMENT 23 MASS FROM FREEZING POINT DEPRESSION EQUIPMENT AND CHEMICALS: Equipment 600 mL beaker Chemicals Cyclohexane (C Stir plate 100 ml. graduated cylinder Clamp Nonvolatile Unknowns Freezing point apparatus Spin vane 0.1 C Thermometer INTRODUCTION: When a solute is introduced into a pure solvent the newly formed solution will have certain physical properties that are from the solvent. As a of the presence of the the pressure of the solution will be lower than that of the pure solvent. As the vapor pressure is lowered there is a resulting increase in the amount of energy required to reach the boiling point of the solution. Conversely, the solution must cool to a lower temperature before a state change from liquid to solid occurs. These changes in physical properties vapor pressure lowering, boiling point elevation and freezing point depression are collectively referred to as colligative properties. These colligative properties, which also include osmotic pressure, do not depend on the nature of the nonvolatile solute in the solution but rather on the concentration of solute present. Because the properties are independent of the nature of the solute, they may be used to determine other properties of the solute such as molecular weight. The effect of a nonvolatile, nonelectrolyte solute on a pure solvent will be examined by finding the freezing point depression of a cyclohexane unknown so solution. The freezing point of a pure sample of cyclohexane will be determined. Introducing a nonelectrolyte solute should in solution formed to freeze at a lower temperature. This temperature will then be experimentally determined As stated the The molality of the solution dependent on the quantity of solute particles present in solution. (moles solute particles per kilogram of solvent) is directly proportional to the change in temperature between the freezing point of the pure solvent and that of the ATfss Kim The molal freezing point depression constant, K for cyclohexane is equal to 20.00 cfmolal By experimentally determining the freezing point depression of a ohexanel unknown solution, the molal concentration is easily calculated. In turn the molar mass of the unknown olute can be calculated as well Chemistry 132 EXPERIMENT23

When a solute is added to a liquid, the boiling point of the resulting solution is __________ than the freezing point of the pure liquid.

A. no different

B. higher

C. lower

When a solute is added to a liquid, the boiling point of the resulting solution is __________ than the freezing point of the pure liquid.

A. higher

B. no different

C. lower

Solution properties are defined as _______________ if the property depends solely on the number of particles of solute and solvent in the solution, not the identity of the solute.

A. vapor pressure

V.colligative

chemical

hydrogen bonding

The advantage of using ________________ rather than the more commonly used unit of ___________________ is that it is independent of temperature effects on density (and thus, volume) of the solution

A. molarity, ppb

B. molarity, % mass

C. molality, molarity

D. molarity, ppm

If a 6.75 g sample of NaCl were dissolved in 8.41 kg of methanol, the molality would be ___________________ m.

A. 0.0137

B. 1.602

C. 0.803

D. 0.0445

The only information needed to determine the freezing point depression of a non-electrolyte is ______________________________ and _________________________________. f

A. the freezing point constant for the solvent, the temperature

B. the boiling point constant, the boiling point elevation

C. the delta T, the color of the most concentrated sample

D. the molality of the solute, the Kf of the solvent

An aqueous solution boils at 100.50oC. What is the freezing point of the solution? Kb(H2O) = 0.51 oC/m; Kf(H2O) = 1.86 oC/m

A. 0.50 oC

B. -0.50 oC

C. -1.82 oC

D. -5.50 oC

Bromoform has a normal freezing point of 7.80 oC and its Kf = 14.4 oC/m. A solution of 2.58 g of an unknown in 100 g of bromoform freezes at 5.43 oC. What is the molecular weight of the unknown?

A. 18.02 g / mol

B. 0.165 g / mol

C. 156 g / mol

D. 44.01 g / mol

Calculate the freezing point of 0.200 m solution of fructose, C6H12O6, a) in water (boiling point, 0 oC), and b) in acetic acid (boiling point, 16.6 oC). Kf(water) = 1.86 oC/m and Kf(acetic acid) = 3.9 oC.

A. -0.372 oC and 15.8 oC

B. -0.958 oC and 12.3 oC

C. 3.221 oC and 0.875 oC

D. -4.124 oC and 0.0035 oC

10.

Calculate the boiling point, in Celsius, at 1atm of a solution containing 30.0 of cane sugar (molecular weight = 342 g / mol) and 150 g of water.

A. 100.30

B. 103.00

C. 99.7

D. 301.00

CHEM 1332 Study Guide - Final Guide: Labatt Brewing Company, Molar Mass, Boiling Point

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