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Quizzes > High School Quizzes > Science

AP Chemistry Unit 5 Progress Check Quiz

Improve Confidence with Focused Chemistry MCQ Practice

Difficulty: Moderate
Grade: Grade 12
Study OutcomesCheat Sheet
Colorful paper art promoting AP Chem MCQ Mashup trivia for advanced high school students.

Which of the following factors most directly increases the rate of a chemical reaction?
Increasing temperature
Decreasing reactant concentration
Increasing activation energy
Removing a catalyst
Increasing temperature raises the energy of reacting molecules, leading to a higher number of effective collisions. This directly increases the reaction rate.
What is the primary role of a catalyst in a chemical reaction?
To lower the activation energy
To increase the overall energy of the system
To be consumed during the reaction
To shift the equilibrium toward products
A catalyst provides an alternative reaction pathway with a lower activation energy, which speeds up both the forward and reverse reactions. It is not consumed during the reaction.
In a reversible reaction at equilibrium, which statement is true?
The concentrations of reactants and products are always equal
The rate of the forward reaction equals the rate of the reverse reaction
The reaction ceases completely
Only reactants are present in the system
At equilibrium, the rates of the forward and reverse reactions are equal, so the concentrations of reactants and products remain constant over time. Equilibrium does not imply that the amounts of reactants and products are equal.
In the Arrhenius equation, what does the constant A represent?
The exponential factor
The activation energy
The frequency factor or collision frequency
The equilibrium constant
The constant A in the Arrhenius equation represents the frequency factor, which relates to how often reacting molecules collide with the proper orientation. It is a measure of the collision frequency that can lead to a reaction.
What defines the equilibrium constant (K) for a reversible reaction?
The ratio of product concentrations to reactant concentrations, each raised to their stoichiometric coefficients
The difference between the concentrations of products and reactants
The sum of the concentrations of products and reactants
The product of the forward and reverse rate constants
The equilibrium constant is defined as the ratio of the concentrations of products to reactants, with each concentration raised to the power of its coefficient from the balanced equation. This constant is fixed at a given temperature for a specific reaction.
Given a reaction with the rate law Rate = k[A]^2[B], what is the overall order of the reaction?
2
3
4
1
The overall reaction order is the sum of the exponents in the rate law. Here, the order with respect to A is 2 and for B is 1, resulting in an overall order of 3.
For the reaction 2A + B → C, if doubling the concentration of A doubles the rate and variations in B have no effect, what are the orders of the reaction with respect to A and B?
Zero order in both A and B
First order in A and zero order in B
Second order in A and first order in B
First order in both A and B
Doubling A and seeing a doubling of rate indicates a first-order dependence in A, while changes in B yield no effect, indicating zero order in B. Therefore, the reaction is first order in A and zero order in B.
In a reaction mechanism, what is the term used for the slowest step that controls the overall rate of reaction?
Fast step
Rate-determining step
Equilibrium step
Chain-initiating step
The slowest step in a reaction mechanism is known as the rate-determining step because it limits how fast the overall reaction can proceed. It essentially sets the pace for the entire reaction.
When a catalyst is added to a chemical reaction, which of the following remains unchanged?
The activation energy
The equilibrium constant
The rate of the reaction
The concentration of products at equilibrium
The addition of a catalyst lowers the activation energy and speeds up both the forward and reverse reactions equally. However, it does not change the equilibrium constant, which is only affected by changes in temperature.
According to collision theory, which of the following is essential for a successful chemical reaction?
Only a high collision frequency
Proper molecular orientation during collision
Sufficient energy and proper orientation during collision
High molar mass of the reactants
Collision theory states that for a reaction to occur, colliding molecules must have both sufficient kinetic energy to overcome the activation energy barrier and the proper orientation for bond rearrangement. Without both factors, effective collisions will not lead to a reaction.
For an exothermic reaction at equilibrium, how does an increase in temperature affect the equilibrium constant?
The equilibrium constant increases
The equilibrium constant decreases
The equilibrium constant remains unchanged
The equilibrium shifts favoring product formation
In an exothermic reaction, heat is released; thus, increasing temperature adds heat to the system. According to Le Chatelier's Principle, the equilibrium shifts to favor the reactants, resulting in a decrease in the equilibrium constant.
For the reaction A ⇌ B, if the concentration of A is increased at equilibrium, Le Chatelier's Principle predicts that:
The equilibrium will shift to produce more A
The equilibrium will shift to produce more B
The equilibrium constant will increase
The reaction will stop
Le Chatelier's Principle states that a system at equilibrium will adjust to counteract any imposed change. Increasing the concentration of A forces the equilibrium to shift to the right, producing more B to re-establish balance.
If a reaction has an activation energy of 50 kJ/mol, what is the effect of increasing the temperature on the molecules' ability to react?
Fewer molecules attain the required energy for a reaction
More molecules attain or exceed 50 kJ/mol, increasing the reaction rate
The activation energy increases proportionally with temperature
The rate constant decreases as the temperature increases
Raising the temperature increases the kinetic energy of the molecules, meaning a larger fraction will have energies equal to or exceeding the activation energy. This results in a higher rate of effective collisions and an increased reaction rate.
Which of the following expressions correctly represents the equilibrium constant K for the reaction 2NO2 ⇌ N2O4?
K = [NO2]^2 / [N2O4]
K = [N2O4] / [NO2]^2
K = [NO2] / [N2O4]^2
K = [N2O4]^2 / [NO2]
The equilibrium constant expression is derived from the balanced chemical equation by placing the concentrations of products in the numerator and those of reactants in the denominator, each raised to the power of their stoichiometric coefficients. For the reaction 2NO2 ⇌ N2O4, K is formulated as [N2O4] / [NO2]^2.
Which graph best describes the progress of concentrations in a reaction reaching equilibrium?
A continuously decreasing reactant concentration with a continuously increasing product concentration
Constant concentrations of reactants and products from the beginning
Decreasing reactant concentration and increasing product concentration that level off to steady values
Oscillating concentrations of reactants and products
A reaction at equilibrium will show the reactant concentration decreasing and the product concentration increasing until both reach constant values. This leveling off of concentrations indicates that the reaction rates of the forward and reverse processes are equal.
Given the mechanism: Step 1: A + B ⇌ C (fast equilibrium) and Step 2: C + A → D (slow), what is the rate law for the overall reaction?
Rate = k[A][B]^2
Rate = k[A]^2[B]
Rate = k[A]^2
Rate = k[A][B]
The slow, rate-determining step is C + A → D, giving an initial rate dependence of [C][A]. Since C is in equilibrium with A and B (from A + B ⇌ C), its concentration can be expressed as proportional to [A][B], leading to an overall rate law of Rate = k[A]^2[B].
In a system with parallel reactions where A transforms into B and C with rate constants k1 and k2 respectively, how does an increase in k1 influence the product distribution?
Decreases the formation of product B
Increases the formation of product C
Increases the selectivity for product B
Does not affect product distribution
An increase in k1 means that reactant A converts to product B at a faster rate compared to the competing pathway to product C. This results in a higher proportion of product B being formed, thereby increasing its selectivity.
When analyzing a plot of ln k versus 1/T for a reaction, what does the slope of this line indicate?
It is equal to Ea × R
It is equal to -Ea/R
It is equal to Ea/R
It is equal to R/Ea
The linearized form of the Arrhenius equation shows that the slope of the plot of ln k versus 1/T is -Ea/R. This negative slope reflects the inverse relationship between the rate constant and the activation energy when temperature is varied.
In an experiment, the reaction rate is found to be zero order with respect to reactant Y. Which of the following scenarios best explains this behavior?
The catalyst's active sites are fully saturated with Y, so its concentration no longer affects the reaction rate
Y does not participate in the reaction mechanism at all
Increasing Y decreases the frequency of effective collisions
Y is rapidly consumed, leading to a zero concentration during the reaction
Zero-order kinetics often occur when a catalyst's active sites are saturated by a reactant, making further increases in its concentration ineffective at altering the reaction rate. This saturation causes the reaction rate to become independent of the concentration of Y.
For an endothermic reaction at equilibrium, what is the effect of increasing temperature on the equilibrium position?
Shifts the equilibrium towards the reactants
Shifts the equilibrium towards the products
No effect on the equilibrium position
Increases the rate constant without shifting equilibrium
In an endothermic reaction, heat is absorbed, so it acts as a reactant. Increasing the temperature adds more heat to the system, causing the equilibrium to shift towards the products to absorb the extra energy. This shift is a direct application of Le Chatelier's Principle.
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Study Outcomes

  1. Analyze chemical reactions to determine equilibrium conditions.
  2. Apply stoichiometric principles to solve quantitative reaction problems.
  3. Interpret thermochemical data to evaluate energy changes in reactions.
  4. Assess reaction kinetics to calculate rate laws and reaction orders.
  5. Demonstrate understanding of molecular structure and bonding to predict chemical behavior.

AP Chem Unit 5 Progress Check MCQ Answers Cheat Sheet

  1. Factors Affecting Reaction Rates - Think of concentration, temperature, and surface area as the turbochargers of chemistry: more particles in a smaller space, plus a little heat, means collisions are both frequent and energetic. Increasing surface area (like crushing solids into powders) gives reactants extra room to mingle. Together, these factors help you predict how fast your reaction will zoom to the finish line. AP Chemistry Unit 5: Kinetics
  2. Mastering the Rate Law Equation - The rate law, Rate = k [A]^x [B]^y, is your experimental GPS: k sets the pace while exponents x and y reveal each reactant's steering power. You'll need lab data to play detective and solve for those mysterious orders. Crack the code and you'll forecast reaction speeds like a kinetics pro. AP Chemistry Unit 5: Kinetics
  3. Determining Reaction Order - To figure out if a reactant is zero-, first-, or second-order, compare how initial rate measurements shift when you tweak concentrations. It's like a puzzle: double [A], note the rate change, and infer the order from the pattern. Mastering this lets you unravel any reaction's secrets. AP Chemistry Unit 5: Kinetics
  4. Integrated Rate Laws - Integrated rate laws link concentration to time, so you can predict how long a reaction takes. Zero-order gives [A] = -kt + [A]₀, first-order follows ln[A] = -kt + ln[A]₀, and second-order obeys 1/[A] = kt + 1/[A]₀. Graph these relationships and watch straight lines reveal your reaction order. AP Chemistry Unit 5: Kinetics
  5. Half-Life Concepts - Half-life (t₝/₂) is the time needed for half your reactant to disappear, and in first-order reactions it stays constant at 0.693/k. It's like a ticking clock that's independent of how much material you started with. Use it to estimate when your reaction punches halfway to completion. AP Chemistry Unit 5: Kinetics
  6. Activation Energy & Catalysts - Activation energy (Ea) is the energy hill reactants must climb to form products - think of it as the workout before the victory lap. Catalysts lower this hill, making reactions sprint without being consumed. Learning how catalysts work can help you design greener, faster processes. AP Chemistry Unit 5: Kinetics
  7. Reaction Energy Profiles - Sketching energy diagrams shows you exothermic dips or endothermic climbs, activation barriers, and the fleeting transition state. These profiles are the roadmap of molecular journeys, highlighting energy changes step by step. Reading them turns you into a pathway explorer. AP Chemistry Unit 5: Kinetics
  8. Reaction Mechanisms - Multistep reactions unfold through elementary steps with intermediates and possible catalysts. By proposing a mechanism and matching its predicted rate law to experiments, you become the chemistry detective solving "how" reactions proceed. It's the blueprint behind every chemical transformation. AP Chemistry Unit 5: Kinetics
  9. Steady-State Approximation - When intermediates form and disappear rapidly, assume their concentration stays relatively constant to simplify complex kinetics. This clever trick turns tangled rate equations into manageable forms. Master it, and even the trickiest mechanisms become solvable. AP Chemistry Unit 5: Kinetics
  10. The Arrhenius Equation - The Arrhenius equation, k = A·e - Ea/RT, links temperature and reaction speed in one elegant formula. A is the frequency factor (how often molecules collide with the right orientation), R is the gas constant, and T is temperature in kelvins. Plot ln k vs. 1/T to extract Ea like a pro thermochemist. AP Chemistry Unit 5: Kinetics
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