Chapter 17 (CHEM 112 Final)

For the reaction A(g) → B(g) + 4 C(g), what is the rate of pressure change for C if the pressure change for A is -0.140 atm/s?

0.56 atm/s

Consider the radioisotope ²³⁵U (half life = 7.04 × 10⁸ years). What is the first order rate constant for ²³⁵U?

9.84 x 10^-10

Copper roofs on houses form patina (copper carbonates) over the course of years due to the reaction with oxygen, carbon dioxide and water in the air. Which of the following statements is incorrect for this process? A) The reaction has a low activation energy. B) The reaction has a low reaction rate. C) The formation of patina would occur faster during the summer than the winter. D) The formation of patina would occur slower at higher altitudes due to lower concentration of reactant. E) Adding a catalyst would increase the rate of patina formation.

A

True of False: A catalyst is consumed in a chemical reaction

False

plot needed for linear fit of rate data (zeroth order)

[A] vs. t

termolecular reaction

elementary reaction involving three reactant species

Greatest rate of appearance deals with products or reactants?

products

A reaction has a rate law of Rate = (1.25 M⁻¹s⁻¹)[A][B]. What is the rate of the reaction if [A] = 0.361 M and [B] = 0.280 M?

0.12635 M/s

The half-life of element X is 500 years. If there are initially 8 g of X, how much will remain after 1500 years?

1 g

what is the integrated rate law for second order reactions?

1/[A] = kt + (1/[A]0)

plot needed for linear fit of rate data (second order)

1/[A] vs. t

For the reaction 3 A + 4 B → 2 C + D, what is the magnitude of the rate of change for [B] when [D] is increasing at 2.7 M/min?

10.8 M/min

The activation energy Ea for a particular reaction is 42.2 kJ/mol. How much faster is the reaction at 343 K than at 323 K? (R = 8.314 J/mol • K)

2.50

Which species has the greatest rate of appearance in the reaction below? 2 H₂S + O₂ → 2 S + 2 H₂O

2S and 2H2O

rate=𝑘[H+][OH−] is what order overall?

2nd

The half-life for the zero order reaction A → Products is 276 s. What is the value of the rate constant for the reaction if the initial concentration of A is 0.205?

3.71 x 10^-4

What is the overall reaction order for the following rate law: Rate = k[A][B][C]²

4

For the reaction 2 A + 4 B → 2 C + 4 D, what is the absolute magnitude of the rate of change for [B] when [C] is increasing at 3.2 M/s?

6.4 M/s

_____ energy is the minimum amount of energy that colliding molecules must possess in order for a chemical reaction to occur. A) activation B) bond C) collision D) reaction

A) activation energy

What affect does temperature have on the rate of a reaction? A) the lower the temperature, the lower the kinetic energy which results in more effective collisions therefore increasing the rate of a reaction B) the higher the temperature, the greater the kinetic energy which results in more effective collisions therefore increasing the rate of a reaction C) the higher the temperature, the greater the kinetic energy which results in more effective collisions therefore decreasing the rate of a reaction D) the lower the temperature, the greater the kinetic energy which results in more effective collisions therefore increasing the rate of a reaction

B

What is the rate law for the reaction A → B if the rate constant, k, is 0.25 M⁻¹ s⁻¹ at 75°C? A) Rate = 0.25 M⁻¹ s⁻¹[A] B) Rate = 0.25 M⁻¹ s⁻¹[A]² C) Rate = 4.0 M⁻¹ s⁻¹[A]² D) Rate = 0.25 M⁻¹ s⁻¹[B] E) Rate = 0.25 M⁻¹ s⁻¹[B]²

B

Which of the following statements is false about catalysts? A) Enzymes are biological catalysts. B) A catalyst is consumed in a chemical reaction. C) A catalyst increases reaction rate by providing an alternate reaction pathway with a lower activation energy. D) A catalyst may undergo change during a reaction but is unchanged at the end of a reaction. E) Catalysts may be homogeneous or heterogeneous.

B

All of the following are factors that affect the rate of a reaction except _____ A) the concentration of the reactants. B) presence of a catalyst. C) the magnitude of the equilibrium constant. D) the temperature of the reaction. E) the surface area of the solid reactants.

C

Which statement is true for the general rate law: Rate = k[A]^m[B]^n A. it can be written from the stoichiometry of the overall reaction B. the overall order of the reaction is equal to m times n C. the values for the exponents must be determined by experiment D. the exponents in the rate law must be positive integers

C

For the reaction 2 A + 3 B → 4 D + 5 E, how is the rate of reaction expressed in terms of rate of disappearance of B? A) ∆[B]/∆t B) -∆B/∆t C) +1/3∆[B]/∆t D) -1/3∆[B]/∆t E) +3∆[B]/∆t

D

The reaction rate of a reaction at 60 °C will be greater than at 30°C because _____ A) the higher temperature leads to greater surface area on solid or liquid reactants. B) the reactants at 60°C will be moving with too great of a speed to collide effectively. C) the activation energy will be lower at 60°C. D) there is a greater proportion of reactants with the necessary kinetic energy to react. E) there is a greater likelihood that the reactants will have the correct orientation to collide effectively.

D

Which of the following affects the collision rate of molecules in the gas phase? A) Speed B) Mass C) Molecular diameter D) All of these affect collision rate E) None of these affect collision rate

D

The Haber Process: N₂ + 3H₂ → 2NH₃ is an important industrial route for the production of ammonia. However, the reaction does not occur fast enough at room temperature to be useful. What could be done to increase the rate of this reaction the most? A) Decrease the temperature B) Add a catalyst C) Increase the temperature D) Decrease the temperature and add a catalyst E) Add a catalyst and increase the temperature

E

Which of the following statements is correct concerning the reaction 2 A + B → 2 C + 2 D? A) The reaction is second order overall. B) The reaction is third order overall. C) The rate is equal to k[A]²[B]. D) The rate is equal to k[A][B]. E) It is not possible to determine the overall order nor the rate law from the given information.

E

What are the units for the rate constant of a second order reaction?

M^-1s^-1

What are the units for the rate constant of a zero order reaction?

Ms^-1

what is the integrated rate law for zeroth order reactions?

[A] = -kt + [A]0

heterogeneous catalyst

catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur

homogeneous catalyst

catalyst present in the same phase as the reactants

What five factors affect reaction rate?

chemical nature of reacting substances, physical state of the reactants, temperature of the reactants, concentrations of the reactants, and the presence of a catalyst

What is the effect on k as the activation energy for a reaction increases?

decreases

unimolecular reaction

elementary reaction involving a single reactant species

bimolecular reaction

elementary reaction involving two reactant species

What is the order of the reaction if A decomposes to B and C with a rate constant of 8.43 × 10⁻⁴ s⁻¹ at a certain temperature?

first order

Which equation should be chosen to produce a straight line with Arrhenius equation?

graph of ln(k) vs. 1/T

initial rate

instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)

Species that are produced in one step and consumed in a subsequent step are called ____________________

intermediates

An instantaneous rate differs from an average rate because?

it's measured at a particular time given specific concentration values

relationship between slope of linear plot and rate constant (first order)

k = -slope

relationship between slope of linear plot and rate constant (zeroth order)

k = -slope

relationship between slope of linear plot and rate constant (second order)

k = slope

what is the integrated rate law for first order reactions?

ln[A] = -kt + ln[A]0

plot needed for linear fit of rate data (first order)

ln[A] vs. t

rate law

mathematical equation showing the dependence of reaction rate on the rate constant and the concentration of one or more reactants

rate of reaction

measure of the speed at which a chemical reaction takes place

activation energy (Ea)

minimum energy necessary in order for a reaction to take place

Rate laws may exhibit fractional orders for some reactants, and ______________ reaction orders are sometimes observed

negative

molecularity

number of reactant species involved in an elementary reaction

The following reaction 2 NO(g) + O₂(g) → 2 NO₂(g) was found to be first order in each of the two reactants and second order overall. The rate law is therefore

rate = k[NO][O₂]

instantaneous rate

rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time

A rate law only includes...

reactants

elementary reaction

reaction that takes place in a single step, precisely as depicted in its chemical equation

What are the units for the rate constant of a first order reaction?

s^-1

The rate determining step is the ________________ step

slowest

rate-determining step

slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction

intermediate

species produced in one step of a reaction mechanism and consumed in a subsequent step

reaction mechanism

stepwise sequence of elementary reactions by which a chemical change takes place

It is important to note that rate laws are determined by experiment only and are not reliably predicted by reaction _________________.

stoichiometry.

catalyst

substance that increases the rate of a reaction without itself being consumed by the reaction

overall reaction order

sum of the reaction orders for each substance represented in the rate law

what is the half-life equation for first order?

t1/2 = 0.693/k

what is the half-life equation for second order?

t1/2 = 1/[A]0k

what is the half-life equation for zero order?

t1/2 = [A]0/2k

Given the following elementary reaction what is the molecularity? A + 2B → AB₂

termolecular

half-life of a reaction

time required for half of a given amount of reactant to be consumed

reaction order

value of an exponent in a rate law (for example, zero order for 0, first order for 1, second order for 2, and so on)