Physical Chemistry Answers

Question 3 : For the following system at equilibrium, what will cause the partial pressure of HF to increase?
U
O
2
(
s
)
+
4
H
F
(
g
)
→
U
F
4
(
g
)
+
2
H
2
O
(
g
)
UO2(s)+4HF(g)→UF4(g)+2H2O(g)

decreasing the pressure
adding
U
F
4
(
g
)
UF4(g)

adding
U
O
2
UO2
(s)
removing
H
2
O
(
g
)
H2O(g)


Question 4 : Equilibrium is a state of dynamic molecular behaviour, meaning that
reactants turn into products and products turn into reactants at different rates.
reactants turn into products and products turn into reactants at equal rates
products continually turn into reactants at a progressively faster rate.
the reaction eventually comes to a stop

Question 1 : The reactions with the high value of energy of activation are
Slow
Fast
Not feasible
Moderate

Question 2 : In general, the rate of a reaction can be increased by all the factors except
Using a catalyst
Increasing the activation energy
Increasing the concentration of reactants
Increasing the temperature

Question 19 : A statement of the second law of thermodynamics is that
energy is conserved in a chemical reaction.
the entropy of the universe is continually increasing.
the enthalpy of reaction is the difference between product and reactant enthalpies.
spontaneous reactions are always exothermic.

Question 20 : The temperature remains constant as energy is added to a substance. How may the substance be changing?
From a gas to a solid
Change in the amoung of kinetic energy
From a liquid to a gas
From a liquid to a solid

Question 17 : Which process is exothermic?
the sublimation of dry ice
the freezing of water
the boiling of liquid nitrogen
the vaporization of water

Question 18 : All of the following processes lead to an increase in entropy EXCEPT
freezing a liquid.
evaporating a liquid.
forming mixtures from pure substances.
increasing the temperature of a gas

Question 15 : Which of the following involves a decrease in entropy?
the dissolution of NaCl in water
the evaporation of ethanol
the freezing of liquid water into ice
the sublimation of carbon dioxide

Question 16 : If a chemical reaction has a positive change in entropy, [Math Processing Error]
ΔS
, then
the disorder of the system increases.
the Gibbs free energy is negative.
heat goes from the system into the surroundings.
the reaction is exothermic.

Question 13 : In a reaction in which the rate of the reverse reaction is equal to the rate of the forward reaction, a state of ____________ is attained.
dynamic equilibrium
total entropy
thermodynamics
product reversibility

Question 14 : Predict the signs of [Math Processing Error]
ΔH
and [Math Processing Error]
ΔS
for the evaporation of water at 35 ^oC.
[Math Processing Error]
ΔH>0
and [Math Processing Error]
ΔS<0

[Math Processing Error]
ΔH<0
and [Math Processing Error]
ΔS<0

[Math Processing Error]
ΔH>0
and [Math Processing Error]
ΔS>0

[Math Processing Error]
ΔH<0
and [Math Processing Error]
ΔS>0

Question 11 : Every type of chemical bond contains a certain amount of energy. The total bond energy, which is essentially equivalent to the total potential energy of the system, is a quantity known as:
entropy.
free energy.
kinetic energy.
enthalpy.

Question 12 : Which reaction is likely to have a negative change in entropy?
[Math Processing Error]
NaCl(s)→Na+(aq)+Cl−(aq)

[Math Processing Error]
2NH3(s)→N2(g)+3H2(g)

[Math Processing Error]
CaO(s)+CO2(g)→CaCO3(s)

[Math Processing Error]
N2O4(g)→2NO2(g)

Question 9 : A reaction with a negative value of [Math Processing Error]
ΔG
is said to be
Reversible
Non-spontaneous
Spontaneous
At equilibrium

Question 10 : Use the equations to answer the question. [Math Processing Error]
2A+B→A2B
[Math Processing Error]
ΔH=–217.3
kJ; [Math Processing Error]
B+C→BC
[Math Processing Error]
ΔH=–867.5
kJ. What is the value of ΔH for the reaction [Math Processing Error]
2A+BC→A2B+C
?
–650.2 kJ
–1084.8 kJ
650.2 kJ
1084.8 kJ

Question 7 : Thermodynamics can be used to determine all of the following EXCEPT
the extent to which a reaction occurs.
the direction in which a reaction is spontaneous.
the temperature at which a reaction is spontaneous.
the rate of reaction.

Question 8 : Calculate the standard entropy change for the following reaction, [Math Processing Error]
2Ag2O(s)→4Ag(s)+O2(g)
; given [Math Processing Error]
So[Ag2O]
= 121.3 J/K·mol, [Math Processing Error]
So
[Ag(s)] = 42.6 J/K·mol, and [Math Processing Error]
So[O2(g)]
= 205.1 J/K·mol.
+126.4 J/K
-126.4 J/K
+132.9 J/K
-205.1 J/K

Question 5 : What does it mean if the [Math Processing Error]
ΔH
value for a chemical reaction is positive?
kinetic energy is increasing in the system
Potential energy is decreasing in the system
products have less potential energy than reactants
reactants have less potential energy than products.

Question 6 : If a process is exothermic and not spontaneous, then what must be true?
[Math Processing Error]
ΔS>0

[Math Processing Error]
ΔG=0

[Math Processing Error]
ΔH>0

[Math Processing Error]