Unit 5 AP Chem

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

X2 + Y2 --> X2Y2 rate = k[X2] A reaction and its experimentally determined rate law are represented above. A chemist proposes two different possible mechanisms for the reaction, which are given below.

  • Only mechanism 2 is consistent with the rate law.
  • Neither mechanism 1 nor mechanism 2 is consistent with the rate law.
  • Only mechanism 1 is consistent with the rate law.
  • Both mechanism 1 and mechanism 2 are consistent with the rate law. (correct)

4 FeS(s) + 7O2(g) --> 2Fe2O3(s) + 4SO2(g)

  • A diagram showing a small activation energy for the forward reaction, typical of a fast reaction.
  • A diagram depicting a large activation energy for the forward reaction, indicating a slow reaction.
  • A diagram with activation energy measured from the products' energy level to the peak of the energy curve, relevant for the reverse reaction.
  • A diagram showing the activation energy extending from the reactants' energy level to the peak of the energy curve, accurately representing the energy barrier. (correct)

A student studying the kinetics of a reaction measures the concentration of reactant X over time. Which procedure will allow the student to determine the rate constant, k, for the reaction?

  • Plot [X] versus time and determine the slope. (correct)
  • Plot 1/[X] versus time and determine the slope.
  • Plot [X]^2 versus time and determine the slope.
  • Plot ln[X] versus time and determine the magnitude of the slope.

For the reaction $C_2H_4 + H_2 \rightarrow C_2H_6$, which action is most likely to increase the rate of reaction?

<p>Adding a heterogeneous catalyst to the reaction system. (A)</p> Signup and view all the answers

In a proposed two-step mechanism for ozone ($O_3$) destruction in the upper atmosphere, what is the expected concentration of intermediate species during the reaction?

<p>CI(g) (B)</p> Signup and view all the answers

How does increasing $[H^+]$ at a constant temperature affect a reaction involving $H^+$ and $ClO^-$ ions?

<p>It increases the frequency of collisions between $H^+$ and $ClO^-$ ions. (D)</p> Signup and view all the answers

Which type of reaction energy profile best represents a two-step exothermic reaction with a fast second step?

<p>A profile with two peaks, where the second peak is lower than the first, indicating a faster second step. (D)</p> Signup and view all the answers

If two solid reactants with varying particle sizes are mixed, what condition results in the fastest reaction rate, assuming the same mass of each reactant in each case?

<p>Small particle sizes at a high temperature. (B)</p> Signup and view all the answers

In an experiment, one student observes a significantly slower reaction rate compared to their peers. Which of the following variations in their procedure could explain this?

<p>Using a 1.5M solution of $HNO_3$ instead of a 15.8M solution. (C)</p> Signup and view all the answers

Two samples of $Mg(s)$ of equal mass react with $HCl(aq)$ in separate vessels. If the $Mg(s)$ is more finely divided in one vessel, how does this affect the reaction, and why?

<p>The reaction will proceed faster where more $Mg(s)$ atoms are exposed to $HCl(aq)$. (B)</p> Signup and view all the answers

What is the primary effect of a solid nickel catalyst on a catalyzed reaction?

<p>The catalyst provides an alternative reaction pathway with a lower activation energy. (B)</p> Signup and view all the answers

In a potential energy diagram for the uncatalyzed decomposition of $H_2O_2(l)$, arrows labeled A and B represent different amounts of energy. With a catalyst present, how do the magnitudes of A and B compare to the uncatalyzed reaction?

<p>Energy A is smaller, and Energy B is unchanged. (B)</p> Signup and view all the answers

For the reaction $2N_2O(g) \rightarrow 2N_2(g) + O_2(g)$ with rate = $k[N_2O]$, what explains why increasing the initial concentration of $N_2O(g)$ increases the reaction rate?

<p>Molecular collisions become more frequent. (D)</p> Signup and view all the answers

Which statement effectively explains why increasing temperature increases the rate of a chemical reaction?

<p>At higher temperatures, high-energy collisions happen more frequently. (A)</p> Signup and view all the answers

For the decomposition of $H_2O_2(aq)$, how can the order of the reaction be determined from experimental data of concentration vs. time?

<p>The reaction is first order if the plot of ln$[H_2O_2]$ versus time is a straight line. (A)</p> Signup and view all the answers

How does a solid catalyst increase the rate of a reaction where the slowest step requires a collision between two gaseous molecules?

<p>The catalyst could adsorb one of the particles, making a successful (reaction-producing) collision with the other particle more likely. (A)</p> Signup and view all the answers

Two trials of a first-order catalytic decomposition of $H_2O_2(aq)$ are performed. If trial 2 has a lower initial rate than trial 1, which factor best explains this difference?

<p>The concentration of $H_2O_2(aq)$ was lower in trial 2 than it was in trial 1. (C)</p> Signup and view all the answers

Given the reaction $2NO(g) + 2H_2(g) \rightarrow N_2(g) + 2H_2O(g)$ with the rate law rate = $k[NO]^2[H_2]$, what is the overall order of the reaction?

<p>Third order (A)</p> Signup and view all the answers

Which change is most likely to increase the rate of reaction between $Li(s)$ and water?

<p>Using a 0.35 g sample of $Li(s)$ cut into small pieces. (B)</p> Signup and view all the answers

For the reaction $NO(g) + NO_3(g) \rightarrow 2NO_2(g)$, which orientation of collision is most likely to be effective?

<p>A collision where the N of NO(g) approaches the O of $NO_3(g)$. (D)</p> Signup and view all the answers

The rate of the reaction $N_2O(g) + CO(g) \rightarrow N_2(g) + CO_2(g)$ increases significantly in the presence of $Pd(s)$. Which best explains this observation?

<p>One of the reactants binds on the surface of $Pd$, which introduces an alternative reaction pathway with a lower activation energy. (C)</p> Signup and view all the answers

For the single-step reaction $NO(g) + NO_3(g) \rightarrow 2NO_2(g)$, a scientist calculates the rate of collisions but finds the observed rate much lower. Which best explains this discrepancy?

<p>The two reactant particles must collide with a particular orientation in order to react. (B)</p> Signup and view all the answers

For the reaction $2NO(g) + Br_2(g) \rightarrow 2NOBr(g)$, two mechanisms are proposed. Which observation would support mechanism 1 but not mechanism 2?

<p>The reaction rate is independent of $[Br_2]$. (C)</p> Signup and view all the answers

For a reaction with rate = $k[NO]^2[H_2]$, what happens to the rate if $[NO]$ is doubled and $[H_2]$ is halved?

<p>The rate is doubled. (C)</p> Signup and view all the answers

Based on the provided data for the decomposition of hydrogen peroxide, $2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)$, how does the rate of $O_2$ production change during the experiment?

<p>The rate decreases throughout the experiment. (B)</p> Signup and view all the answers

A student observes that without $MnO_2(s)$, the reaction is much slower. Which statement best explains this?

<p>$MnO_2(s)$ provides a reaction pathway with a lower activation energy. (A)</p> Signup and view all the answers

For the reaction $X(g) + 2Y(g) \rightarrow XY_2(g)$, which reactant is consumed more rapidly in trial 2, and why?

<p>Y, because the rate of disappearance will be double that of X. (C)</p> Signup and view all the answers

How can the difference between reaction path one and reaction path two for the decomposition of XY2 be best explained?

<p>The presence of a catalyst in path two. (C)</p> Signup and view all the answers

Consider the reaction $2X + 2Z \rightarrow X_2Z_2$. During a reaction with excess X, the plot of ln[Z] versus time is linear. What is the reaction order with respect to Z?

<p>First order (B)</p> Signup and view all the answers

For the single-step reaction $NO_2Cl(g) + Cl(g) \rightarrow NO_2(g) + Cl_2(g)$, what factor will reduce the value of k, the rate constant?

<p>Decreasing the temperature (B)</p> Signup and view all the answers

Flashcards

Rate-determining Step

The slowest step in a reaction mechanism that determines the overall rate of the reaction.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed in the process. Provides an alternate reaction pathway with a lower activation energy.

Activation Energy

Energy required to start a chemical reaction. Catalysts lower this energy

Reaction Mechanism

A series of elementary steps that describe the pathway of a reaction.

Signup and view all the flashcards

Rate Law

A mathematical expression that shows how the rate of a reaction depends on the concentration of reactants. Rate = k[A]^m[B]^n

Signup and view all the flashcards

Temperature Coefficient

The factor by which the rate of a reaction increases when the temperature is raised by 10 °C.

Signup and view all the flashcards

Elementary Reactions

Reactions that occur in one step.

Signup and view all the flashcards

Collision Orientation

The specific orientation of molecules during a collision necessary for a reaction to occur.

Signup and view all the flashcards

Exothermic Reaction

A reaction where the products have lower energy than the reactants, releasing heat to the surroundings.

Signup and view all the flashcards

Endothermic Reaction

A reaction where the products have higher energy than the reactants, requiring heat from the surroundings.

Signup and view all the flashcards

Heterogeneous Catalyst

A catalyst existing in a different phase than the reactants. (e.g. solid catalyst, gas reactants)

Signup and view all the flashcards

Homogeneous Catalyst

A catalyst existing in the same phase as the reactants. (e.g. all aqueous)

Signup and view all the flashcards

Reaction Order

The sum of the exponents in the rate law, indicating how concentration affects rate.

Signup and view all the flashcards

Equilibrium

A state where the rate of forward and reverse reactions are equal, resulting in no net change in concentrations.

Signup and view all the flashcards

Entropy (S)

A measure of molecular disorder or randomness in a system

Signup and view all the flashcards

Study Notes

  • X2+Y2 --> X2Y2 has a rate of k[X2]

  • Mechanisms 1 and 2 are both consistent with the rate law

  • 4FeS(s) + 7O2(g) --> 2Fe2O3(s) + 4SO2(g) : The combustion of some types of coal results in the formation of SO2(g) due to the presence of FeS(s).

  • SO2(g) + O3(g) --> SO3(g) + O2(g): SO2(g) can react with O3(g) to form SO3(g)

  • ΔH-298 = -242kJ/molrxn and ΔS-298 = -25J/(K·molrxn)

  • A student studies the kinetics of X --> Products by measuring [X] over time

  • Plotting ln[X] versus time and finding the magnitude of the slope allows for determination of the rate constant, k

  • For C2H4 + H2 --> C2H6, adding a heterogenous catalyst to the reaction system is most likely to increase the reaction rate

  • In a two-step mechanism for the destruction of ozone (O3) in the upper atmosphere the concentration is very low for the duration of the reaction

  • Increasing [H+] at constant temperature increases the frequency of collisions between H+ ions and ClO- ions.

  • A reaction energy profile with two steps and is exothermic best corresponds to the proposed mechanism

  • For two solid reactants of varying particle size combined in a vessel a small black dots temperature of 950C will give the fastest reaction rate

  • In one student's experiment the reaction proceeded at a much slower rate than it did in the other student's experiments because the student used a 1.5M solution of HNO3 instead of a 15.8 solution of HNO3.

  • 2 samples of Mg(s) of equal mass were placed in equal amounts of HCl(aq)

  • More Mg atoms are exposed to HCl(aq) in Figure 2 than in Figure 1, therefore Figure 2's reaction will proceed faster

  • With a solid nickel catalyst, the catalyst's presence results in a reaction pathway that needs lower activation energy

  • 2 N2O(g) --> 2 N2(g) + O2(g) with rate = k[N2O]. Increasing initial [N2O] at constant temperature increases reaction rate because molecular collisions become more frequent

  • At higher temperatures, high-energy collisions happen more frequently, explaining why the rate of a chemical reaction increases with increasing temperature.

  • Hâ‚‚Oâ‚‚(aq) --> 2H2O(l) + O2(g) with ΔH = -196 kJ/mol,m

  • If the plot of ln [Hâ‚‚Oâ‚‚] versus time is a straight line, then the reaction is first order

  • The collision must be successful to lead to increased reaction rate: the catalyst could adsorb one of the particles, making a successful (reaction-producing) collision with the other particle more likely

  • Rate = k[H2O2]: catalyzed decomposition of H2O2 (aq)

  • Trial 2's concentration of H2O2 (aq) was lower than that of Trial 1

  • 2 NO (g) + 2 H2 (g) --> N2 (g) + 2 H2O (g), with a rate law of k[NO]^2[H2]

  • Overall order of reaction: third order

  • If a 0.35 g sample of Li(s) is cut into small pieces, it will have the most likely increase the rate of reaction between Li(s) and water

  • For the reaction between NO(g) + NO3(g) --> 2NO2(g),the diagram that correctly shows the orientation of collision between NO(g) and NO3(g) is most likely to be effective is (D)

  • Nâ‚‚O(g) + CO(g) --> Nâ‚‚(g) + COâ‚‚(g): the rate increases significantly in the presence of Pd(s) because One of the reactants binds on the surface of Pd, which introduces an alternative reaction pathway with a lower activation energy

  • For NO(g) + NO3(g) --> 2 NO2(g); rate = k[NO][NO3], the two reactant particles must collide with a particular orientation to react

  • 2 NO(g) + Br2(g) --> 2 NOBr(g): if the reaction rate is independent of [Br2] then that would support mechanism 1 but not mechanism 2

  • 2 NO(g) +2 H2(g) --> N2(g) + 2 H2O (g), Rate = k[NO]^2[H2]. If [NO] is doubled and [H2] is halved the rate doubles

  • A student measures the volume of O2(g) produced by 2 H2O2(aq) -->2 H2O(l) + O2(g) at regular intervals while the temperature is held constant: the rate of O2 production decreases throughout the experiment.

  • If a student observes that under the same conditions, H2O2(aq) decomposes in the presence of MnO2(s) occurs faster than without MnO2(s), it is because MnO2(s) provides a reaction pathway with a lower activation energy

  • X(g) + 2Y(g) --> XY2(g): in trial 2 Y is consumed more rapidly because the rate of disappearance will be double that of X

  • XY2 --> X + Y2: presence of a catalyst in path two would most likely account for the difference between reaction path one and path two.

  • 2 X + 2 Z --> X2Z2: With excess X, but Z is monitored over time: plot of the natural logarithm is shown, the reaction with respect to reactant Z is first order

  • NOâ‚‚Cl (g) + Cl (g) --> NO2 (g) + Cl2 (g): Decreasing the temperature of the sealed container will reduce the value of k, the rate constant for the reaction.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

More Like This

Use Quizgecko on...
Browser
Browser