Question

a. The standard enthalpy of vaporization of an inorganic
compound is 38.9 kJ/mol. If the temperature at which this phase
change occurs is 221.72 °C, determine ΔS°_{vap} (in
J/mol/K) for this compound. Report your answer to three significant
figures.

b. The entropy of freezing of an organic compound is -21.0
J/mol/K. If ΔH°_{freez} is -14.01 kJ/mol, determine the
temperature (in K) at which this phase change occurs. Report your
answer to two decimal places

Answer #1

(a). Standard enthalpy of vaporization, H^{o}_{vap}
= 38.9 kJ/mol

= 38900 J/mol

Temperature = 221.72 oC = 494.87 K

S^{o}_{vap}
= H^{o}_{vap}
/ T

= 38900 / 494.87

**S ^{o}_{vap}
= 78.6 J/mol.K**

(b). S^{o}_{fus}
= - 21.0 J/mol.K

H^{o}_{fus}
= -14.01 kJ/mol = - 14010 J/mol

S^{o}_{fus}
= H^{o}_{fus}
/ T

T = - 14010 / - 21

= 667.14 K

**Temperature = 667.14 K**

For mercury, the enthalpy of vaporization is 58.51 kJ/mol and
the entropy of vaporization is 92.92 J/K*mol. What is the normal
boiling point of Hg in degrees celcius? The enthalpy change for
this process would be + or -? The free energy change for this
process would be + or -?

The enthalpy of vaporization of methanol is 35.27 kJ/ mol at
64.1 oC. Determine the entropy change in the system for
the vaporization of 2.00 moles of methanol. What is the entropy
change in the surroundings (assume Tsurr = 25
oC.)

he thermodynamic properties for a reaction are related by the
equation that defines the standard free energy, ΔG∘, in
kJ/mol:
ΔG∘=ΔH∘−TΔS∘
where ΔH∘ is the standard enthalpy change in kJ/mol and
ΔS∘ is the standard entropy change in J/(mol⋅K). A good
approximation of the free energy change at other temperatures,
ΔGT, can also be obtained by utilizing this
equation and assuming enthalpy (ΔH∘) and entropy
(ΔS∘) change little with temperature.
Part A
For the reaction of oxygen and nitrogen to...

Calculate ΔvapH , the molar enthalpy of vaporization,
of a substance at 338.15 K,
given that its standard enthalpy of vaporization is Δvap
Hθ = 32.45 kJ mol−1 vap at 25.0ºC.
The heat capacities are Cp,mliq = 46.20 J
K−1 mol−1 for the liquid and
Cp,mvap = 32.20 J K−1
mol−1 for the vapor.

Consider the following data for compound A:
(delta)Hf(kj/mol) S(J/K*mol)
A(s) -224.57 32.36
A(l) -172.45 109.55
Use these data to determine the normal freezing point of
compound A. Report your answer to 3 significant figures and degrees
Celsius)
Freezing point =

The enthalpy of fusion for Lauric acid (C12H24O2) is 32.86
kJ/mol and enthalpy of vaporization is 63.82 kJ/mol. The melting
point is 43.2 degrees C. How much heat is absorbed to raise the
temperature of a 0.650g sample from 22.0 degrees C to 56.3 degrees
C? The heat capacity of the solid is 2.15 J/g degrees C and the
heat capacity of the liquid is 3.62 J/g degrees C

A liquid has an enthalpy of vaporization of 30.8 kJ/mol. At 273
K it has a vapor pressure of 102 mmHg. What is the normal boiling
point of this liquid? (R = 8.31 J/(K· mol))

If the temperature of the surroundings is -244.32 °C, calculate
the entropy change (in J/K) for the system (ΔSsys), surroundings
(ΔSsur) and universe (ΔSuniverse) when 40.4 g of liquid oxygen (O2)
freezes. Report your answers to two decimal places. Tfus(°C)
-218.79 Tvap(°C) -182.96 ΔH°fus (kJ/mol) 0.44 ΔH°vap (kJ/mol)
6.82

If the temperature of the surroundings is 38.36 °C, calculate
the entropy change (in J/K) for the system (ΔSsys), surroundings
(ΔSsur) and universe (ΔSuniverse) when 48.1 g of gaseous carbon
tetrachloride (CCl4) condenses. Report your answers to two decimal
places.
Tfus(°C) -23.00
Tvap(°C) 76.80
ΔH°fus (kJ/mol) 3.28
ΔH°vap (kJ/mol) 29.82

For a given reaction, ΔH = -26.6 kJ/mol and ΔS = -77.0 J/K⋅mol.
The reaction is spontaneous ________. Assume that ΔH and ΔS do not
vary with temperature.
For a given reaction, = -26.6 kJ/mol and =
-77.0 J/Kmol. The reaction is spontaneous ________. Assume
that and do not vary with temperature.
at T > 298 K
at all temperatures
at T < 345 K
at T < 298 K
at T > 345 K

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