Practice Quiz Chapter 20If you miss more than three, you should study more befor taking the on-line quiz.You may retake this test as many times as you like.
Which relationship or statement best describes ΔS° for the following reaction?2NH3(g) + 2ClF3(g) → 6HF(g) + N2(g) + Cl2(g)
ΔS° ≈ 0
ΔS° < 0
ΔS° > 0
ΔS° = ΔH°/T
More information is needed to make a reasonable prediction.
In tables of thermodynamic data provided in chemistry books, one finds ΔH° f , ΔG° f and S° listed. Briefly, explain why the entropy data are supplied as S°, while the enthalpy and free energy data are in the form of ΔH° f and ΔG° f, respectively.
When a sky diver free-falls through the air, the process is
non-spontaneous because he is accelerating due to the force applied by gravity.
non-spontaneous because he is losing potential energy.
non-spontaneous because he had planned the jump for two weeks.
spontaneous.
in equilibrium.
In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.
1 mole of F2(g); 1 mole of Cl2(g)
1 mole of I2(s); 1 mole of I2(g)
1 mole of CaCO3(s); 1 mole of CaO(s) plus 1 mole of CO2(g)
1 mole of H2(g) at 25°C; 1 mole of H2(g) at 50°C
1 mole of O3(g); 1 mole of O2(g)
Which of the following is always true for an exothermic process?
q sys > 0, ΔSsurr < 0
q sys < 0, ΔSsurr > 0
q sys < 0, ΔSsurr < 0
q sys > 0, ΔSsurr > 0
w < 0
a. Explain what is meant by a spontaneous process.b. Is a spontaneous process necessarily a rapid one? Explain, and provide a real reaction as an example to illustrate your answer.
The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid.H3PO4(s) ↔ H3PO4(l)Use the following thermodynamic data at 298 K to determine this temperature.
Substance
H3PO4(s)
H3PO4(l)
ΔH° f (kJ/mol)
-1284.4
-1271.7
ΔG° f (kJ/mol)
-1124.3
-1123.6
S°(J/K⋅mol)
110.5
150.8
286 K
305 K
315 K
347 K
3170 K
In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.
1 mole He(g); 1 mole Kr(g)
1 mole O2(g); 2 mole O(g)
1 mole CH4(g); 1 mole C2H6(g)
1 mole Xe(g) at 1 atmosphere; 1 mole Xe(g) at 0.5 atmosphere
20 one-dollar bills distributed randomly among 20 people; 20 one-dollar bills distributed randomly among 10 people
In a spontaneous process, the entropy of the system always increases.
Which relationship best describes ΔS° for the following reaction?CO(g) + H2O(g) → CO2(g) + H2(g)
ΔS° = ΔH°
Nitric oxide reacts with chlorine to form NOCl. The data refer to 298 K.2NO(g) + Cl2(g) → 2NOCl(g)
NO(g)
Cl2(g)
NOCl(g)
90.29
0
51.71
86.60
66.07
210.65
223.0
261.6
What is the value of ΔG° for this reaction at 550 K?
-143.76 kJ
-78.78 kJ
-22.24 kJ
-10.56 kJ
66600 kJ
Which relationship or statement best describes ΔS° for the following reaction? CaO(s) + CO2(g) → CaCO3(s)
You are given pure samples of pentane, CH3CH2CH2CH2CH3(l), and 1,3-pentadiene, M CH2=CHCH=CHCH3(l). What prediction would you make concerning their standard molar entropies at 298 K?
S°pentane > S°1, 3-pentadiene
S°pentane < S°1, 3-pentadiene
S°pentane ≈ S°1, 3-pentadiene
S°pentane ? S°1, 3-pentadiene + 2 ×
More information is needed to make reasonable predictions.
Which relationship best describes ΔS° for the following reaction?8H2(g) + S8(s) → 8H2S(g)
For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?
ΔS° > 0, ΔH° > 0
ΔS° > 0, ΔH° < 0
ΔS° < 0, ΔH° < 0
ΔS° < 0, ΔH° > 0
It is not possible for a reaction to be spontaneous at all temperatures.
This is the end of the test. When you have completed all the questions and reviewed your answers, press the button below to grade the test.