CHEM 104 MODULE 3 – QUESTIONS AND
ANSWERS | VERIFIED AND WELL
DETAILED ANSWERS PLUS S | EXAM PREP |
STUDY GUIDE | ORIGINAL PRACTICE
QUESTIONS
1. Which statement best describes a reversible chemical reaction?
A. It proceeds only in the forward direction.
B. It proceeds only in the reverse direction.
C. It can proceed in both the forward and reverse directions under the same
conditions.
D. It stops immediately after the reactants are mixed.
A reversible reaction allows both the forward and reverse reactions to occur.
Under appropriate conditions, the system may reach dynamic equilibrium.
2. What is meant by dynamic equilibrium in a chemical reaction?
A. The reaction has stopped completely.
B. Reactants have been completely consumed.
C. The forward and reverse reaction rates are equal.
D. The concentrations of reactants are zero.
At dynamic equilibrium, both reactions continue to occur, but at equal rates, so
the concentrations of reactants and products remain constant.
3. Which factor does NOT change the value of the equilibrium constant (K)
for a reaction?
,A. Temperature
B. Pressure
C. Catalyst
D. Reaction enthalpy
A catalyst speeds up both the forward and reverse reactions equally, allowing
equilibrium to be reached more quickly without changing the equilibrium
constant.
4. According to Le Châtelier's Principle, what happens if additional reactant
is added to a system at equilibrium?
A. The equilibrium shifts toward the reactants.
B. The equilibrium shifts toward the products.
C. The equilibrium constant increases.
D. The reaction stops.
The system responds by consuming some of the added reactant, shifting the
equilibrium toward product formation.
5. Which statement best describes an exothermic reaction?
A. It absorbs heat from the surroundings.
B. It releases heat to the surroundings.
C. It has no energy change.
D. It occurs only at high temperatures.
,Exothermic reactions release thermal energy to the surroundings, resulting in a
negative enthalpy change (ΔH).
6. Which quantity measures the heat change occurring at constant pressure?
A. Entropy
B. Enthalpy
C. Free energy
D. Internal energy only
Enthalpy (H) is the thermodynamic quantity used to describe heat transfer at
constant pressure.
7. A reaction has ΔH = –125 kJ/mol. Which statement is correct?
A. The reaction is endothermic.
B. The reaction absorbs heat.
C. The reaction releases 125 kJ of heat per mole of reaction.
D. The reaction cannot occur spontaneously.
A negative enthalpy change indicates that heat is released to the surroundings
during the reaction.
8. Which factor increases the rate of most chemical reactions?
A. Lowering the temperature
B. Decreasing reactant concentration
, C. Increasing temperature
D. Removing the catalyst
Higher temperatures increase molecular kinetic energy, resulting in more
frequent and energetic collisions that increase reaction rate.
9. According to collision theory, a chemical reaction occurs only when
reacting particles
A. Touch each other.
B. Have sufficient energy and proper orientation.
C. Contain identical atoms.
D. Are in the solid state.
Effective collisions require enough energy to overcome activation energy and
the correct orientation for bond formation and breaking.
10. What is activation energy?
A. The total energy released by a reaction.
B. The minimum energy required for a reaction to occur.
C. The energy stored in products only.
D. The energy of the catalyst.
Activation energy is the energy barrier that reacting particles must overcome for
a successful reaction to occur.
11. Which effect does a catalyst have on activation energy?
ANSWERS | VERIFIED AND WELL
DETAILED ANSWERS PLUS S | EXAM PREP |
STUDY GUIDE | ORIGINAL PRACTICE
QUESTIONS
1. Which statement best describes a reversible chemical reaction?
A. It proceeds only in the forward direction.
B. It proceeds only in the reverse direction.
C. It can proceed in both the forward and reverse directions under the same
conditions.
D. It stops immediately after the reactants are mixed.
A reversible reaction allows both the forward and reverse reactions to occur.
Under appropriate conditions, the system may reach dynamic equilibrium.
2. What is meant by dynamic equilibrium in a chemical reaction?
A. The reaction has stopped completely.
B. Reactants have been completely consumed.
C. The forward and reverse reaction rates are equal.
D. The concentrations of reactants are zero.
At dynamic equilibrium, both reactions continue to occur, but at equal rates, so
the concentrations of reactants and products remain constant.
3. Which factor does NOT change the value of the equilibrium constant (K)
for a reaction?
,A. Temperature
B. Pressure
C. Catalyst
D. Reaction enthalpy
A catalyst speeds up both the forward and reverse reactions equally, allowing
equilibrium to be reached more quickly without changing the equilibrium
constant.
4. According to Le Châtelier's Principle, what happens if additional reactant
is added to a system at equilibrium?
A. The equilibrium shifts toward the reactants.
B. The equilibrium shifts toward the products.
C. The equilibrium constant increases.
D. The reaction stops.
The system responds by consuming some of the added reactant, shifting the
equilibrium toward product formation.
5. Which statement best describes an exothermic reaction?
A. It absorbs heat from the surroundings.
B. It releases heat to the surroundings.
C. It has no energy change.
D. It occurs only at high temperatures.
,Exothermic reactions release thermal energy to the surroundings, resulting in a
negative enthalpy change (ΔH).
6. Which quantity measures the heat change occurring at constant pressure?
A. Entropy
B. Enthalpy
C. Free energy
D. Internal energy only
Enthalpy (H) is the thermodynamic quantity used to describe heat transfer at
constant pressure.
7. A reaction has ΔH = –125 kJ/mol. Which statement is correct?
A. The reaction is endothermic.
B. The reaction absorbs heat.
C. The reaction releases 125 kJ of heat per mole of reaction.
D. The reaction cannot occur spontaneously.
A negative enthalpy change indicates that heat is released to the surroundings
during the reaction.
8. Which factor increases the rate of most chemical reactions?
A. Lowering the temperature
B. Decreasing reactant concentration
, C. Increasing temperature
D. Removing the catalyst
Higher temperatures increase molecular kinetic energy, resulting in more
frequent and energetic collisions that increase reaction rate.
9. According to collision theory, a chemical reaction occurs only when
reacting particles
A. Touch each other.
B. Have sufficient energy and proper orientation.
C. Contain identical atoms.
D. Are in the solid state.
Effective collisions require enough energy to overcome activation energy and
the correct orientation for bond formation and breaking.
10. What is activation energy?
A. The total energy released by a reaction.
B. The minimum energy required for a reaction to occur.
C. The energy stored in products only.
D. The energy of the catalyst.
Activation energy is the energy barrier that reacting particles must overcome for
a successful reaction to occur.
11. Which effect does a catalyst have on activation energy?
