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Gen Chem II > Chapter 17 Thermodynamics > Flashcards

Chapter 17 Thermodynamics Flashcards

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1
Q

Consider a reaction that has a negative H and a negative S. Which of the following statements is TRUE?

a. This reaction will be spontaneous only at high temperatures.
b. This reaction will be spontaneous at all temperatures.
c. This reaction will be nonspontaneous at all temperatures.
d. This reaction will be nonspontaneous only at high temperatures.
e. It is not possible to determine without more information.

A

d. This reaction will be nonspontaneous only at high temperatures.

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2
Q

Calculate Grxn at 298 K under the conditions shown below for the following reaction.

a. +341 kJ
b. +17.8 kJ
c. +332 kJ
d. -47.4 kJ
e. -109 kJ

A

a. +341 kJ

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3
Q

Identify the process that is spontaneous

rusting of iron

electrolysis

photosynthesis

bread rising

burning gasoline

A

rusting of iron

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4
Q

Use Hess’s law to calculate G°rxn using the following information.

a. +753.5 kJ
b. +277.0 kJ
c. -676.0 kJ
d. -1152.5 kJ
e. -225.7 kJ

A

c. -676.0 kJ

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5
Q

The ________ Law of Thermodynamics states the entropy of a perfect crystal at absolute zero is zero.

Zero

First

Second

Third

Fourth

A

Third

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6
Q

Determine the equilibrium constant for the following reaction at 655 K.

a. 3.99 × 1012
b. 13.0
c. 2.51 × 10-13
d. 3.26 × 10-12
e. 3.07 × 1011

A

b. 13.0

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7
Q

Calculate S°rxn for the following reaction. The S° for each species is shown below the reaction.

a. +112.3 J/K
b. +550.9 J/K
c. -112.3 J/K
d. +337.1 J/K
e. -550.9 J/K

A

a. +112.3 J/K

Delta S = (prod)-(react)
219.3-200.9-130.7 = 112.3 J/K

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8
Q

The ________________ Law of Thermodynamics states that for any spontaneous reaction, the entropy of the universe increase.

A

2nd

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9
Q

The _______________ Law of Thermodynamics sates the energy is conserved in chemical processes.

A

1st

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10
Q

Consider a reaction that has a positive H and a negative S. Which of the following statements is TRUE?

a. This reaction will be spontaneous only at high temperatures.
b. This reaction will be spontaneous at all temperatures.
c. This reaction will be nonspontaneous at all temperatures.
d. This reaction will be nonspontaneous only at high temperatures.
e. It is not possible to determine without more information.

A

c. This reaction will be nonspontaneous at all temperatures.

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11
Q

Consider a reaction that has a positive H and a positive S. Which of the following statements is TRUE?

a. This reaction will be spontaneous only at high temperatures.
b. This reaction will be spontaneous at all temperatures.
c. This reaction will be nonspontaneous at all temperatures.
d. This reaction will be nonspontaneous only at high temperatures.
e. It is not possible to determine without more information.

A

a.This reaction will be spontaneous only at high temperatures.

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12
Q

Place the following in order of decreasing molar entropy at 298 K.

a. H2 > Cl2 > F2
b. Cl2 > H2 > F2
c. F2 > Cl2 > H2
d. H2 > F2 > Cl2
e. Cl2 > F2 > H2

A

e. Cl2 > F2 > H2

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13
Q

Identify the statement that is FALSE.

a. The entropy of a gas is greater than the entropy of a liquid.
b. Entropy generally increases with increasing molecular complexity.
c. Free atoms have greater entropy than molecules.
d. Entropy increases with dissolution.
e. For noble gasses, entropy increases with size.

A

c. Free atoms have greater entropy than molecules.

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14
Q

Choose the statement below that is TRUE.

a. K > 1, G°rxn is positive.

b. K

A

d. Grxn = 0 at equilibrium.

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15
Q

Below what temperature does the following reaction become nonspontaneous?

a. 39.2 K
b. 151 K
c. 475 K
d. This reaction is nonspontaneous at all temperatures.
e. This reaction is spontaneous at all temperatures.

A

c. 475 K

delta G = delta H - T delta S
delta G > 0
delta H/ delta S > T

+136.5 KJ /
+287.5E-3 KJ/K >T

474.78 > T

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16
Q

Determine the equilibrium constant for the following reaction at 298 K.

  1. 66 × 105
  2. 986
  3. 96 × 10-7
  4. 98 × 10-4
  5. 12 × 106
A

1.12 × 106

17
Q

What is true if ln K is negative?

Gorxn is positive and the reaction is spontaneous in the forward direction.

Gorxn is negative and the reaction is spontaneous in the forward direction.

Gorxn is negative and the reaction is spontaneous in the reverse direction.

Gorxn is positive and the reaction is spontaneous in the reverse direction.

Gorxn is zero and the reaction is at equilibrium.

A

Gorxn is positive and the reaction is spontaneous in the reverse direction.

18
Q 
The thermodynamic quantity that expresses the degree of disorder in a system is \_\_\_\_\_\_\_\_\_\_.
A) entropy
B) internal energy
C) heat flow
D) enthalpy
E) bond energy
A

A) entropy

19
Q 
Which one of the following is always positive when a spontaneous process occurs?
A) ΔHuniv 
B) ΔHsurr 
C) ΔSsurr 
D) ΔSuniv
 E) ΔSsys
A

D) ΔSuniv

20
Q

DS will be positive for the reaction __________.

A) 2H2 (g) + O2 (g) => 2H2O (g)
B) 2NO2 (g) => N2O4 (g)
C) BaF2 (s) => Ba2+ (aq) + 2F- (aq)
D) 2Hg (l) + O2 (g) => 2HgO (s)
E) CO2 (g) => CO2 (s)
A

C) BaF2 (s) => Ba2+ (aq) + 2F- (aq)

21
Q

Which one of the following processes produces a decrease in the entropy of the system?

A) dissolution of solid KCl in water
B) mixing of two gases into one container
C) freezing water to form ice
D) melting ice to form water
E) boiling water to form steam
A

C) freezing water to form ice

22
Q

Of the following, the entropy of gaseous __________ is the largest at 25eC and 1 atm.

A) C2H2 
B) H2 
C) C2H6 
D) CH4
E) C2H2
A

C) C2H6

23
Q

What can be said about a chemical system that has reached a minimum in free energy?

A) The reaction is complete.
B) The system entropy is zero.
C) The system has achieved equilibrium.
D) The temperature is OK.
E) The reaction is very fast.
A

C) The system has achieved equilibrium.

24
Q

State Function

A

Thermodynamic quantity dependent on the MOMENT, ie: T, P, V, and is independent of path or hx.

25
Q

A process related to disorder and randomness at a molecular level

A

d

Gen Chem II (3 decks)

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