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-The heat needed to vaporize a liquid depends on (it's heat capacity or amount).

-Which of the following statements is correct? a) Unsaturated solutions are relatively unstable. Supersaturated solutions are relatively unstable. c) A solution becomes saturated when the solute dissociates completely to ions. d) All of these statements are correct. e) None of these statements are correct.

-Cubic closest packing coordination number? & number of atoms.

-the equilibrium vapor pressure of a liquid depends on it's temperature or external pressure.

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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.

For which system below would quantum effects be leastnoticeable?

-The collision of two N₂ molecules in a gas, whichchanges the rotational energy of both

-Polarization of the electron density of ethanol resulting inexcitation of vibrational motions

-An electron-sized particle moving in a 1 m³ box asthe temperature decreases by 10 degrees

-A hydrogen atom being struck by a UV photon

We have dealt with two different ensembles, canonical andmicrocanonical. Which of the following statements is inaccurateregarding these ensembles?

-The canonical ensemble is always considered as a subset of alarger reservoir, which acts as the surroundings.

-The microcanonical ensemble is defined to have constant energy,volume, and composition.

-The microcanonical ensemble is a smaller subset of microstatesof the canonical ensemble.

-The canonical ensemble is generally more useful than themicrocanonical for chemical processes.

Which statement below is most correct regarding the partitionfunction of an ensemble?

-For a given temperature, the high-energy contributions to thepartition function are more heavily weighted.

-Once a partition function is defined in a specific ensemble, itis valid in all other ensembles.

-It tells us the numerical order of the energy levels for agiven system.

-It provides a measure of the energy levels available to asystem at a given temperature.

Consider a cup-carrier from your favorite take-out restaurant.The carrier can hold four cups, and you have to place two cups (onelarge, one small) into the carrier, with no preference forposition. How many microstates can you form with two cups in thefour spaces?

-12

-8

-16

-6

Boltzmann's definition of the entropy was a breakthrough inunderstanding statistical thermodynamics. What is the bestdefinition of Boltzmann's entropy?

-The Boltzmann entropy is a count of the total distinctmicrostates in a system.

-The Boltzmann entropy is a measure of the randomness of anensemble.

-The Boltzmann entropy is a count of the accessible energylevels at a given temperature.

-The Boltzmann entropy is a measure of the useful work availablein an ensemble.

Our canonical ensemble was defined such that the temperature,volume, and number of particles were each held constant. In termsof the Legendre transform, which thermodynamic potential isfundamental in the canonical ensemble?

-The Helmholtz energy

-The internal energy

-The Gibbs energy

-The enthalpy

The equipartition principle can be used to estimate the constantvolume heat capacities of gases. Under which circumstances wouldthe full equipartition heat capacity most closelyapproximate the measured value of C_V?

-A sample of N₂ gas at 373K

-A sample of propane gas (C₃H₈) at roomtemperature

-A sample of water vapor at 373K

-A sample of Br₂ vapor at room temperature

Which factor below does not contribute to the rotationalpartition function of a molecule?

-The rotational quantum number

-The nuclear and electronic spin states

-The rotational constant(s)

-The temperature of the molecule

We were able to reduce the vibrational partition function froman infinite series to a function of a single exponential, but onlyapproximately. Which approximation below was NOT used?

-We assumed that the vibrational energy can be expressed asv?_e.

-We assumed that the energy levels were close enough to allowintegration instead of summation.

-We assumed that the vibrational motion is purely harmonic.

-We assumed that the separations are relatively small, due tohigh temperature or lower vibrational constant.

The derived partition function for an ideal gas depends on allof the physical parameters listed below except for which one?

-Molecular symmetry

-The temperature of the molecules

-The volume of the sample

-Mass of the molecules

Deriving the translational partition function is more involvedthan deriving the rotational and vibrational partition functions.Which statement below is NOT a reason for this?

-There are so many possible translational energy levels, thatthe integral does not converge to a finite value.

-The integral of translational states for a single particle mustbe taken over a 6-dimensional hypervolume.

-The degeneracy of translational states is not obvious becausethey lie so close in energy.

-Translational degrees of freedom involve interactions betweenall molecules in the sample, whereas rotations and vibrations donot.

The connection between the Equipartition Principle and thetranslational partition functions helped to demonstrate that thetemperature of a system depends on the easily excited degrees offreedom. Why should this be true?

-In systems with easily excited degrees of freedom, a change inthe entropy requires energy changes on the order of thermalenergy.

-In systems with easily excited degrees of freedom, smallincreases in the pressure make excited states more accessible,

increasing the temperature.

-In systems with easily excited degrees of freedom, thepotential energy is no longer dependent on the temperature of thesystem.

-In systems with easily excited degrees of freedom, thermalenergy is sufficient to allow one to treat the energy levels as acontinuum.

The connection between the Maxwell-Boltzmann distribution andthe translational partition function allowed us to betterunderstand the distribution of speeds. Which statement below is NOTa consequence of the translational partition function?

-The population of the lowest speeds is very small.

-The pressure of the gas increases as the velocityincreases.

-An increase in the temperature will result in shifting thedistribution to higher energies.

-The population of the highest speeds is very small.

When dealing with quantum energy levels, there are severalimportant factors to consider. Which concept below is NOT importantto quantum energy levels?

-The set of quantum numbers

-Degeneracy

-The deBroglie wavelength

-The ground state

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