Chem 103 Final Exam Questions and
Accurate Answers
Which letter corresponds to the Activation Energy for the reverse reaction? - Answer: D
Which letter corresponds to the energy level that would be altered by the addition of a catalyst? -
Answer: C
Which correctly describes the reverse reaction? - Answer: it's exothermic, and "delta H" would be
negative
For an endothermic reaction, the Activation Energy for the forward reaction is greater than the
Enthalpy change ("delta H"). - Answer: true
Which letter corresponds to the Activation Energy for the forward reaction? - Answer: B
Which letter corresponds to the amount of energy released/absorbed when the reaction occurs? -
Answer: E
Which correctly describes the forward reaction? - Answer: . it's endothermic, and "delta H" would
be positive
In the reaction A + B <==> AB, the state of equilibrium is achieved when... - Answer: There is some A
and B plus there is some AB and these amounts not longer change with further increases in time.
How does temperature affect reaction rate? - Answer: As temperature goes up, reaction rate goes
up, because more molecules have more kinetic energy which increases the effectiveness of the
molecular collisions to promote a reactions.
A reversible reaction is said to have attained equilibrium, when: - Answer: Both backward and
forward reactions take place at equal speed.
What is the effect of a catalyst on the reaction rate. - Answer: Catalysts increase the reaction rate
often by attaching to one of the reactions which makes collisions with the second reactant molecule
,more effective for product formation. Yes, catalysts can help to overcome the orientation problem of
polar molecules.
What is the equilibrium constant expression for the following reaction? 2 NOCl (g) <==> 2 NO (g) +
Cl2 (g) - Answer: Keq = [NO]^2 [Cl2] / [NOCl]^2
What is the equilibrium constant expression for the following reaction? 2 BrCl (g) <==> Br2 (g) + Cl2
(g) - Answer: Keq = [Br2] [Cl2] / [BrCl]^2
Calculate the value of Keq given the equation H2 (g) + I2 (g) <==> 2 HI (g). Assume at equilibrium H2
= 0.200 M, I2 = 0.200 M and HI = 0.040 M. - Answer: . Keq = 0.04
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: more HCl gas is added to the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would adding HCl to the reaction container affect the concentration of HI gas? -
Answer: increase
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: Cl2 gas is removed from the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would removing Cl2 from the reaction container affect the concentration of HCl
gas? - Answer: decrease
Which statement best describes a reaction system that has reached equilibrium? - Answer: A. the
forward and reverse reactions have stopped
B. the rates of the forward and reverse reactions are equal
C. the concentrations of the reactants and products have stopped changing
D. the concentrations of the reactants and products are equal
E. more than one is correct
, Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: the external pressure is increased, so that the volume
of the container decreases.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would increasing the pressure / decreasing the volume affect the concentration of
HCl gas? - Answer: increase
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: the reaction system is heated by placing the reaction
chamber in an hot water bath.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would increasing the temperature affect the concentration of HCl? - Answer:
decrease
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: more HCl gas is added to the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would adding HCl to the reaction container affect the amount of I2solid in the
reaction mixture? - Answer: decrease
Which is the correct Equilibrium Constant expression for this reaction? N2 (g) + 3 F2 (g) ⇔ 2 NF3 (g) -
Answer: K = [NF3]2 / [N2] [F2]3
What is an Arrhenius base? - Answer: An Arrhenius base is a compound that ionizes in water to
produce hydroxide ion. Feedback: Yes, ionizes and OH-
What is the hydronium ion? - Answer: . The hydronium ion is H3O+ Feedback: Yes, water with an
extra proton and a plus charge.
Accurate Answers
Which letter corresponds to the Activation Energy for the reverse reaction? - Answer: D
Which letter corresponds to the energy level that would be altered by the addition of a catalyst? -
Answer: C
Which correctly describes the reverse reaction? - Answer: it's exothermic, and "delta H" would be
negative
For an endothermic reaction, the Activation Energy for the forward reaction is greater than the
Enthalpy change ("delta H"). - Answer: true
Which letter corresponds to the Activation Energy for the forward reaction? - Answer: B
Which letter corresponds to the amount of energy released/absorbed when the reaction occurs? -
Answer: E
Which correctly describes the forward reaction? - Answer: . it's endothermic, and "delta H" would
be positive
In the reaction A + B <==> AB, the state of equilibrium is achieved when... - Answer: There is some A
and B plus there is some AB and these amounts not longer change with further increases in time.
How does temperature affect reaction rate? - Answer: As temperature goes up, reaction rate goes
up, because more molecules have more kinetic energy which increases the effectiveness of the
molecular collisions to promote a reactions.
A reversible reaction is said to have attained equilibrium, when: - Answer: Both backward and
forward reactions take place at equal speed.
What is the effect of a catalyst on the reaction rate. - Answer: Catalysts increase the reaction rate
often by attaching to one of the reactions which makes collisions with the second reactant molecule
,more effective for product formation. Yes, catalysts can help to overcome the orientation problem of
polar molecules.
What is the equilibrium constant expression for the following reaction? 2 NOCl (g) <==> 2 NO (g) +
Cl2 (g) - Answer: Keq = [NO]^2 [Cl2] / [NOCl]^2
What is the equilibrium constant expression for the following reaction? 2 BrCl (g) <==> Br2 (g) + Cl2
(g) - Answer: Keq = [Br2] [Cl2] / [BrCl]^2
Calculate the value of Keq given the equation H2 (g) + I2 (g) <==> 2 HI (g). Assume at equilibrium H2
= 0.200 M, I2 = 0.200 M and HI = 0.040 M. - Answer: . Keq = 0.04
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: more HCl gas is added to the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would adding HCl to the reaction container affect the concentration of HI gas? -
Answer: increase
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: Cl2 gas is removed from the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would removing Cl2 from the reaction container affect the concentration of HCl
gas? - Answer: decrease
Which statement best describes a reaction system that has reached equilibrium? - Answer: A. the
forward and reverse reactions have stopped
B. the rates of the forward and reverse reactions are equal
C. the concentrations of the reactants and products have stopped changing
D. the concentrations of the reactants and products are equal
E. more than one is correct
, Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: the external pressure is increased, so that the volume
of the container decreases.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would increasing the pressure / decreasing the volume affect the concentration of
HCl gas? - Answer: increase
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: the reaction system is heated by placing the reaction
chamber in an hot water bath.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would increasing the temperature affect the concentration of HCl? - Answer:
decrease
Imagine the reactants HCl and I2 are placed in a reaction chamber. The endothermic forward
reaction begins, and after a period of time, the system reaches equilibrium.
2 HCl (g) + I2 (s) ⇔ 2 HI (g) + Cl2 (g)
Now a change is made to shift the equilibrium: more HCl gas is added to the reaction container.
Use LeChatelier's Principle to predict the shift in the equilibrium.
Specifically, how would adding HCl to the reaction container affect the amount of I2solid in the
reaction mixture? - Answer: decrease
Which is the correct Equilibrium Constant expression for this reaction? N2 (g) + 3 F2 (g) ⇔ 2 NF3 (g) -
Answer: K = [NF3]2 / [N2] [F2]3
What is an Arrhenius base? - Answer: An Arrhenius base is a compound that ionizes in water to
produce hydroxide ion. Feedback: Yes, ionizes and OH-
What is the hydronium ion? - Answer: . The hydronium ion is H3O+ Feedback: Yes, water with an
extra proton and a plus charge.
