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12 Dec 2019

A pure substance with a molar mass of 0.122 kg/mol has solid and liquid phases with

densities of 1.08Ã ~103 kg/m3 and 1.01Ã ~103 kg/m3, respectively, at its standard melting point of

427. K. The standard boiling point for this pure substance is 550. K, with a molar enthalpy

of vaporization of 2.20Ã ~104 J/mol.

a. The melting point for this pure substance increases to 429. K if the pressure is increased

to 1.20Ã ~107 Pa. Determine Î fusSm (in J/mol-K) for the substance, assuming both Î fusSm & Î fusVm are independent of temperature and pressure.

b. Determine the boiling point (in K) for this pure substance when the pressure is 2.00 bar.

c. The standard boiling point rises by 2.00 K when 2.00 mol of naphthalene is dissolved in 10.0 kg of the substance. Determine whether naphthalene experiences net dissociation, net association, or neither in this solvent based on the apparent vanât Hoff factor for naphthalene in this substance, assuming the solution is sufficiently dilute.

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Keith LeannonLv2

13 Dec 2019

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Related questions

1. The vapor pressure of a substance is measured over a range of temperatures. A plot of the natural log of the vapor pressure versus the inverse of the temperature (in Kelvin) produces a straight line with a slope of â3.54Ã103 K . Find the enthalpy of vaporization of the substance. Express your answer using three significant figures.

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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.

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