Question 1
(1 point)
Determine the value of H° in kJ for the following reaction: 2SO2(g) + O2(g) --> 2SO3(g)
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"-198 kJ"
198 kJ
99 kJ
"-99 kJ"
"-357"
Question 2 (1 point)
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Use the following thermochemical equations
C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O(l) H= -1367 kJ
H2(g) + 1/2O2(g) --> H2O(l) H = -286 kJ
C(graphite) + O2(g) --> CO2(g) H= -394 kJ
to calculate the standard enthalpy of formation for the following reaction:
2C(g) + 3H2(g) + 1/2O2(g) --> C2H5OH(l)
+279 kJ/mol
+687 kJ/mol
+680 kJ/mol
-279 kJ/mol
+2047 kJ/mol
Question 3
(1 point)
Which of these samples of gas has the highest entropy?
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2 mol of methane gas occupying 2 L
1 mol of methane gas occupying 1 L
Each of these samples has the same amount of entropy because they are at the same
pressure.
1 mol of ethane gas occupying 1 L
2 mol of ethane gas occupying 2 L
Question 4
(1 point)
Calculate The delta H for the syntheis of diborane (B2H6) from its elements using the following
data:
2B(s) + 3/2O2(g) --> B2O3(s) -1273 kJ
B2H6(g) +3O2(g) -->B2O3(s) + 3H2O(g) -2035 kJ
H2(g) +1/2O2(g) --> H2O(l) -286 kJ
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H2O(l) --> H2O(g) 44 kJ.
36 kJ
14 kJ
378 kJ
-378 kJ
760 kJ
Question 5 (1 point) Save
Considering the equation ΔG = ΔH -TΔS, in which scenario MUST the reaction be spontaneous? All
scenarios describe only the system.
Entropy decreases and enthalpy increases
Entropy increases and enthalpy increases
Entropy increases and enthalpy decreases
Entropy decreases and enthalpy decreases
Entropy and Enthalpy remain constant
Question 6
Which of the following is NOT true about a spontaneous process?
(1 point)
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The free energy of the reaction is less than zero
The entropy of the universe increaeses
The reaction is exothermic
The reverse reaction is always non spontaneous under the same reaction conditions
Whether a reaction is spontaneous can be changed by altering reaction conditions.
Question 7
(1 point)
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In the metallurgy of antimony, the pure metal is recovered via different reactions, depending on the
composition of the ore.
For example, iron is used to reduce antimony in sulphide ores:
Sb2S3(s) +Fe(s) --> 2 Sb(s) +3FeS(s) Δ H = -125 kJ, What is the Δ S(surroundings) for this
reaction at 25° C and 1 atm?
419 J/K
"-419 J/K"
5 J/K
"-5 J/K"
125 kJ
Question 8 (1 point)
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In the metallurgy of antimony, the pure metal is recovered via different reactions, depending on the
composition of the ore.
For example, carbon is used to reduce antimony in oxide ores:
Sb4O6(s) +6C(s) --> 4Sb(s) +CO(g) Δ H = 778 kJ What is the Δ S(surroundings) for this reaction
at 25 °C and 1 atm?
31.2 kJ/K
-31.2 kJ/K
-778 kJ
-2.61 kJ/K
2.61 kJ/K
Question 9 (1 point)
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Methanol is a fuel used in racing car engines and fuel cells. Calculate Δ G for the reaction
2CH3OH(l) + 3O2(g) --> 2CO2 (g) + 4H2O(g)
using the following free energies of formation :
CH3OH(l) -163 kJ/mol
CO2 (g) -394 kJ/mol
O2(g) 0 kJ/mol
H2O(g) -229 kJ/mol.
-1378 kJ
- 460kJ
-1500 kJ
-765 kJ
-980 kJ
Question 10 (1 point) Save
In which case does the entropy of the system decrease significantly?
C(s) + O2(g) --> CO2(g)
N2(g) + 3H2(g) --> 2NH3(g)
CaCO3(s) --> CaO(s) + CO2(g)
H2O(l) --> H2O(g)
SnO2(s) + 4C(s) --> Sn(s) + 4CO2(g)
Question 11
(1 point)
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Some standard entropies (at 25°C in J/mol K) are given in the following list: diamond 2.43, O2(g)
205.0, CO(g) 197.9. The value of S° for the reaction:
2C(diamond) + O2(g) -->
2CO(g) at 25°C in J/K is
-9.5 J K-1
390.9 J K-1
-185.9 J K-1
+185.9 J K-1
+9.5 J K-1
Question 12
Calculate G° in kJ at 350°C for the reaction:
(1 point)
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2NO2(g) --> N2O4(g)
For NO2(g) Hf° = 33.18 kJ/mol and S°= 240.1 J/molK For N2O4(g) Hf° = 9.16 kJ/mol and S° =
304.3 J/molK
-413 kJ
-64.0 kJ
52.4 kJ
4.37 kJ
1.10 x 105 kJ
Question 13
Calculate S in J/K for the reaction:
(1 point)
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C(s) + O2(g) --> CO2(g)
S° J/molK = 5.69 for C(s), 205 for O2(g) and 213.6 for CO2(g)
-424.3 J/K
424.3 J/K
2.9 J/K
-2.9 J/K
Question 14 (1 point)
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Choose the scenario where q>0, w<0 and ΔU <0
A reaction attached to a piston pushes up on the piston and moves it for 70 kJ of
work and the system cools down absorbing 30 kJ of heat from its surroundings
A reaction attached to a piston pushes up on the piston and moves it for 14 kJ of
work and the system releases 30 kJ of heat to the surroundings.
A piston pushes down on a reaction decreasing the volume inside the reaction vessel
for 15 kJ of work and 10 kJ of heat is released by the system
A reaction attached to a piston pushes up on the piston and moves it for 14 kJ of
work and the system cools down absorbing 30 kJ of heat from its surroundings.
A battery is attached to a reaction vessel and does electrical work (10 kJ) on the
system which then undergoes a 50 kJ exothermic reaction.
Question 15
(1 point) Save
Which of the following processes are spontaneous and which are nonspontaneous: (i) separation of
gaseous N2 and O2 molecules from each other, (ii) the reaction of sodium metal with chlorine gas
to form sodium chloride, (iii) the dissolution of HCl(g) in water to form concentrated hydrochloric
acid?
(i) nonspontaneous (ii) spontaneous , (iii) spontaneous
(i) nonspontaneous (ii) nonspontaneous , (iii) spontaneous
(i) spontaneous (ii) spontaneous , (iii) spontaneous
(i) nonspontaneous (ii) spontaneous , (iii) nonspontaneous