Chem Ch 14 and some of 15
Consider the reaction of ammonia with oxygen gas, a balanced equation for which is given below. 4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g) How are the rate of consumption of oxygen gas and the rate of production of NO related? Select all responses that apply. 1)O2 is consumed 1.25 times faster than NO is produced. 2)O2 is consumed at 0.80 the rate that NO is produced. 3)NO is produced at 0.80 the rate of O2 is consumed. 4) O2 is produced 1.25 times faster than NO is consumed. 5) -1/5O2=1/4NO 6) 1/5O2=1/4NO
1 and 5
What are the linear kinetic formulas for each order? How does the slope relate?
1 order= ln[A] -k=slope 2nd order= 1/[A] k=slope 0 order= [A] -k=slope
How do the following manipulations effect the equilibrium constant? 1) Reversing the reaction 2) Summing two reactions to determine K for overall reaction 3)Changing coefficients
1) Divide K by 1 (1/K) 2) Multiply the K values of each individual reaction together 3) Scale the K constant by the same factor NOTE: k doesn't equal K
An elementary process has an activation energy of 92 kJ/mol. If the free energy change for the reaction is -62 kJ/mol, what is the activation energy for the reverse reaction? Enter your response in kilojoules per mole (kJ/mol) to the nearest 1 kJ/mol.
154 DRAW IT OUT.
What does the half lives for 1st,2nd, and zero order reactions depend on?
1rst order only depends on the constant k (rate constant) and the half life for 1rst order is always constant despite concentration. 2nd order and 0 order reactions depend on both concentration remaining and the rate constant. However, second order reaction half lives are directly proportional to the rate constant while zero order half lives are indirectly proportional to the rate constant
Phosphine, PH3, is a colorless, toxic gas that is used in the production of semiconductors as well as in the farming industry. When heated, phosphine decomposes into phosphorus and hydrogen gases. 4PH3(g)⟶P4(g)+6H2(g) This decomposition is first order with respect to phosphine, and has a half‑life of 35.0 s at 953 K. Calculate the partial pressure of hydrogen gas that is present after 64.8 s if a 6.00 L vessel containing 2.34 atm of phosphine gas is heated to 953 K.
2.54
The decomposition of a given chemical compound obeys first-order kinetics with t1/2 = 5 hours. How many hours (hr) must elapse for the initial concentration of the compound to reach 1/16 of its original value? Enter your response to the nearest 1 hr.
20
The rate constant for this first‑order reaction is 0.0760 s−1 at 400 ∘C. A⟶products After how many seconds will 16.0% of the reactant remain?
24
The first half-life for a given reaction is 2.5 minutes and the third half-life is 10.0 minutes. What is the kinetic order for this reaction?
2nd order because the half life of a first order reaction is constant and is not dependent on concentration. This leaves 0 order and 2nd order as remaining option. Then, knowing THAT HALF LIFE DOUBLES FOR 2ND ORDER REACTIONS, one can determine that the rate order for this reaction is 2.
The frequency factor A accounts for which of the following? Select all that apply. Group of answer choices 1)The fraction of collisions that occur with Ecollision > Ea 2)How often collisions occur 3)The fraction of collisions having molecular orientation that leads to the formation of desired product
3 and 2
Which statement is true of a chemical reaction in dynamic equilibrium? Group of answer choices 1)The concentration of reactants is equal to the concentration of products. 2)The rate constant kfwd for the forward reaction is equal to the rate constant krev for the reverse reaction. 3)The amounts (in moles) of reactants and products are equal. 4)The rate of the forward reaction is equal to the rate of the reverse reaction. 5)All of the reactants are consumed and the forward reaction stops. 6)Both the forward and reverse reactions stop.
4
In the Arrhenius equation, the term e^-Ea/RT is most closely related to which of the following? Group of answer choices 1)The raw number of molecular collisions in a system 2)The fraction of collisions that result in chemical reaction 3)The rate of collisions 4)The fraction of collisions that occur with enough energy to overcome the activation energy 5)The fraction of collisions that occur with "proper" molecular orientation
4 because the e part of the equation dictates energy while the A frequency constant dictates the fraction and rate of collisions that occur with proper orientation.
heterogeneous catalyst
A catalyst in a different phase than the reactants.
homogeneous catalyst
A catalyst in the same phase as the reactants.
equilibrium constant, K
A constant that tells how far a reaction will proceed until it reaches equilibrium.
transition state
A high-energy state in rearrangement of bonds occurs during chemical reactions; also called activated complex.
intermediate
A high-energy, unstable species formed by one intermediate step and consumed by the next intermediate step in a reaction mechanism.
Apply collision theory to derive the Arrhenius equation to appreciate the conceptual bases of terms in the equation.
A represents the rate of collisions and which fraction of collisions occur with proper orientation. e^-Ea/RT represents the fraction of collisions that occur with proper energy. Entire equation dictates rate constant.
Use the graph below to determine the instantaneous rate of production of B at t = 20 seconds. Enter your response in units of molarity per second (M/s) to the nearest 0.0001 M/s. Graph points= (40,0.07) and (20, 0.03)
0.0015
The rate law for the reaction 2 A(g) → A2(g) at a given temperature is: rate = (0.0054 M/s)[A]0 What is the rate of this reaction at the same temperature?
0.0054
The rate of production of N2(g) in the reaction below is 0.016 M/s. 2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g) What is the standard rate of reaction? Enter your response in units of molarity per second (M/s) to the nearest 0.001 M/s.
0.016
The rate of production of N2(g) in the reaction below is 0.016 M/s. 2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g) What is the rate of consumption of H2(g)? Enter your response in units of molarity per second (M/s) to the nearest 0.001 M/s.
0.032
The reaction A+B⟶C+D rate=𝑘[A][B]^2 has an initial rate of 0.0150 M/s. What will the initial rate be if [A] is halved and [B] is tripled?
0.0675
What is the stoichiometric coefficient of NO2 in the overall reaction corresponding to the mechanism depicted in the first question? Enter your response as a numeral. NO2 + NO2 ⇄ NO3 + NO (fast) NO3 + CO → NO2 + CO2 (slow)
1
Which statement best describes activation energy? Group of answer choices 1) The difference in energy between the transition state and the reactants. 2) The difference in energy between the transition state and the products. 3) The absolute energy of the transition state. 4) The difference in energy between reactants and products
1
Which statement best describes what it means for a reactant to be "first order"? Group of answer choices 1)The concentration of that reactant and rate of reaction are linearly related. 2)The reaction rate is independent of the concentration of that reactant. 3)The concentration of that reactant and reaction rate are exponentially related.
1
Which statement(s) explain why a collision between molecules may NOT result in a chemical reaction? Select all that apply. Group of answer choices 1)The collision occurs with a molecular orientation that does not facilitation formation of the bonds in the desired products. 2)The collision occurs with too much kinetic energy. 3)The collision doesn't occur at the right pressure.
1
Consider the Arrhenius equation: Which statements are true? Select all that apply. Group of answer choices 1)Rate constant increases as temperature increases. 2)Rate constant decreases as activation energy increases 3)Rate constant decreases as temperature increases. 4)Rate constant increases as activation energy increases.
1 and 2
Which statement(s) is or are true regarding collision theory? Select all that apply. Group of answer choices 1)Molecules with the correct collision orientation may collide without resulting in a chemical reaction. 2)Molecular collisions that occur with kinetic energy that exceeds the energy of the transition state must result in chemical reactions. 3)Molecules must collide to react.
1 and 3
What statements are true regarding initial rates? 1) The use of initial rates permits us to ignore the concentration of products during chemical reactions 2) The use of initial rates permits us to ignore the concentration of reactants during chemical reactions 3) All instantaneous rates can be accurately defined as initial rates 4) The initial rate at t=0 is an example of an instant rate.
1 and 4
Identify kinetic order using graphical analysis of the dependence of reactant concentration on time.
Basically be able to determine x and y values and be able to plug in given information to predict values of other information given a graph. Also know the slopes of graphs and which linearization equates to which rate order----> First order= ln[A] and slope=-k Second order= 1/[A] and slope=k Zero order= [A] and slope= -k
Use reaction mechanisms to derive rate laws for overall reactions.
Basically use the rate determining step and that is the overall reaction rate of the mechanism. If there is an intermediate present, utilize equilibrium rules to rewrite that intermediate in terms of other reactants.
Describe how catalysts work to speed up chemical reactions.
Catalysts are NOT used up in a reaction but enable reactants to follow a path that enable the reaction to occurs with less energy.
Which portion of a graph depicts an intermediate?
Dips in between multiple transition states
Define and explain the condition of chemical equilibrium.
Equilibrium occurs when the rate of the forward reaction is equivalent to the rate of the reverse reaction. The rate constants ARE NOT similar.
Correlate reaction rate with molecular-level behavior through exploration of collision theory.
Essentially, the collision theory and the Arrhenius equation dictate relationships between activation energy, k, and reaction rate. The following is true: Higher Ea= Slower reaction Higher k value= faster reaction higher reaction rate= faster reaction rate
How do you determine when equilibrium began for a reaction from a graph?
From the point at which both the concentration of reactants and products are constant as mentioned in the law of mass action.
How do you determine activation energy from a plot
From where the reactant or products (if equilibrium) are to up the parabola to the curve. It is the transition state minus the position of what your starting with.
How do you determine the units for the rate constant?
Generally, the following will be true Rate order 1= time^-1 Rate order 0= M time^-1 Rate order 2= M^-1s^-1 Note that the exponent on time will never change, it will always be negative one. However, the exponent on M for second order rates will change as it will be one minus the overall order except for if its one.
Deduce the kinetic order of a reactant from the units of the rate constant.
If its (MTime^-1) Then its zero order. If its (time^-1) then its first order. If its (M^-1Time^-1 then its second order. For second order, the units on M is 1 minus the overall order of the reaction which is the sum of all orders for each reactant
Identify intermediates in a reaction mechanism.
Intermediates are just products of 1 step of a reaction that are then used up as the reactants of another step
Predict the concentration and time values of reactions using zero-, first-, and second-order integrated rate laws.
Just means that you should know how to use the integrated rate laws of each rate order to predict how much of a reactant remains after a certain amount of time given other information. First order= ln[At]=-kt+ln[A0] Second order= 1/[At]=kt+1/[A0] Zero order= [At]=-kt+[A0]
What does the following mean- K=1 K>1 K<1
K=1 means neither reactants or products are favored. Doesn't necessarily mean that there will be a split amount of reactants and products at equilibrium K>1 means the reaction will produce more products to get to equilibrium K<1 means that the reaction will produce more reactants to get to equillibrium
How can the equilibrium constant for pressure be expressed in terms of the the equilibrium constant for concentration?
Kp=Kc(RT)^n n= coefficients of products-reactants
units of reaction rate
M/s or mol/L*s
What would be the units of the rate constant for a reaction that has an overall order of 18?
M^-17s^-1
A mixture of 0.421 M H2, 0.436 M I2, and 0.872 M HI is enclosed in a vessel and heated to 430 °C. H2(g)+I2(g)↽−−⇀2HI(g)𝐾c=54.3 at 430 Calculate the equilibrium concentrations of each gas at 430 ∘C.
Make ICE table. H2=0.177M I2=0.192M HI=1.36M
At a certain temperature, 0.345 mol CH4 and 0.637 mol H2O is placed in a 3.50 L container. CH4(g)+2H2O(g)↽−−⇀CO2(g)+4H2(g) At equilibrium, 7.26 g CO2 is present. Calculate 𝐾c
Make an ICE table and the answer is 0.15
A 3.21 mol sample of NO2(g) is added to a 3.75 L vessel and heated to 500k. N2O4(g)↽−−⇀2NO2(g)𝐾c=0.513 at 500K Calculate the concentrations of NO2(g) and N2O4(g) at equilibrium.
NO2=0.357 N2O4=.24921
Identify the intermediates in the reaction mechanism in the previous question.
NO3
What represents transition states on a graph?
Peaks
relationship between Q and K and K itself?
Q>K more reactants needed Q<K More products needed K=Q then system is at equilibrium K>1 then there are more products at equilibrium K<1 then there are more reactants at equilibrium K=1 then there are equal amounts of products and reactants at equilibrium
instantaneous rates
Reaction rates determined by graphing concentration, time, drawing a tangent to the curve and determining the slope of the tangent.
average rates
Reaction rates determined by measuring the concentration at two different times and dividing the change in concentration by the change in time.
For a given reaction, a plot of of ln k (y-axis) versus 1/T (x-axis, with T in Kelvin) is linear with line of best fit y = -41285x + 32.643. What is the activation energy of this reaction based on this result? Enter your response in kilojoules per mole (kJ/mol) to the nearest 0.1 kJ/mol.
Remember that the slope of this plot equal -Ea/R where R=8.3145. The answer is 343.2. Don't forget to divide by 1000 as the units of R are in joules and the answer requires an answer in KJ.
A particular gas-phase reaction has an equilibrium constant of 𝐾p=0.50. A mixture is prepared where all the reactants and products are in their standard states. Which direction will the reaction proceed?
Since all the reactants are in the standard state, k=1 because standard state refers to elements/reactants that are at 1 atm or 1mol. Then because the measured Qc is greater than the Kc, more reactants will be produced.
The diagrams represent the equilibrium mixture for the reaction X2(g)+Y(g)↽−−⇀X(g)+XY at 600 K and 800 K. The X atoms are represented using red spheres, and the Y atoms are represented using blue spheres. Is the reaction exothermic or endothermic? There are more reactants at the higher temperature
Since there are more reactants at the higher temperature, this is an exothermic reaction because you increased heat (a product in exothermic reactions) and got more reactants. This just follows along Chateliers Principle which dictates that when a system is under stress, it will move to relieve that stress. When you increase products at equilibrium you will get more reactants. When you increase reactants at equilibrium, you will get more products.
Consider the reaction mechanism below. Which elementary step has a rate expression that will match the observed differential rate law of the reaction? A + B → C + D (fast, equilibrium) A + D → C (slow)
Step 2
HUGE MISCONCEPTION
THE RATE ORDER OF A REACTANT IS NOT ITS COEFFECIENT
What can effect the equilibrium constant and actually cause it to shift in value for a reaction?
Temperature is the only thing. Changes in concentration, pressure, or volume will simply shift the reaction to produce more products or reactants.
orientation
The arrangement of molecules as they approach for a collision, where the proximity of certain atoms dictates whether the reaction can occur.
Consider the linear version of the first-order integrated rate law: ln [A]t = -kt + ln [A]0 What does the term [A]t represent?
The concentration left at a certain time, t.
rate constant, k
The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation.
initial rate
The instantaneous rate measured at time zero.
What other aspects of a catalyzed reaction are different from the uncatalyzed reaction? 1)the overall reaction 2)the mechanism 3)Δ𝐸rxn
The mechanism can be different but the other two are the same. The change in energy is the same as reactants and products both finish at the same level of energy despite or with a catalyst
activation energy
The minimum amount of energy needed for the reactant to reach the transition state; also called barrier energy.
The rate constant for a given reaction is k = 0.312 M-1 s-1. If the initial concentration of reactant is 1.00 M, what is the length of the third half-life? Enter your response in seconds (s) to the nearest 0.1 s.
The order is second. Thus use the formula t(1/2)= 1/k[A0] You must do this formula with k[A0] equal to 0.5M because you want the initial concentration that leads up to the third half life. The answer is 12.8
law of mass action
The ratio of products to reactants in the equilibrium constant expression does not change as long as the system is at equilibrium.
equilibrium constant expression
The ratio of the product of the concentrations of the products divided by the product of the concentrations or partial pressures of the reactants, each raised to the power corresponding to its coefficient in the balanced equation. Also referred to as an equilibrium expression.
reaction quotient, Q
The ratio of the products to the reactants, where each species is raised to its stoichiometric coefficient, at any time in an equilibrium. Can be used to determine which direction the reaction is heading shown in the following: Q=K, the system is in equilibrium and there is no shift Q>K, the system is favored to produce mor reactants Q<K, the system if favored for more products Think in terms of Q
dynamic state
The reactants are continuously forming products and the products are continuously forming reactants
Predict which of the following reactions has the higher activation energy. N2(g) + 3 H2(g) → 2 NH3(g) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)
The second reaction as it has more bonds that need to be broken
equilibrium
The situation in which the forward and reverse reactions are occurring at the same rate. EQULIBRIUM CONSTANTS ARE NOT EQUIVALENT, RATES ARE
overall reaction order
The sum of the reaction orders for the individual reactants
half-life
The time needed for one-half of the reactant to be consumed by a reaction
What represents the activation energy of a reaction on a graph?
The transition state-energy position of reactants
How do you determine which two trials are best to determine order rate for a reactant?
The trials in which everything else has a constant molarity except for the reactant that you are measuring the rate order for. You want that to change so you can measure how changing that effects reaction rate which is how to determine rate order.
The reaction A → B + C has k = 0.034 s-1 at 25° C. If [A]0 = 2.40 M, then what is [A] after 4.2 s? Enter your response in units of molarity (M) to the nearest 0.01 M.
The unites indicate a first order reaction. Thus, the formula ln[A(t)]= -kt + ln[A0] will be used. Plug in given information to calculate the value of [x]. The answer is 2.08 Note: The (t) isn't actually plugged in
A 2.0 L vessel contains 0.75 moles of N2O5 at a given temperature. The rate constant at the temperature of reaction is 0.00052 s-1. How many moles of NO2 does the vessel contain after 5.0 minutes? Enter your response to the nearest 0.01 mol. 2 N2O5(g) → 4 NO2(g) + O2(g)
The units indicate a first order reaction and thus you will use the formula ln[A(t)=-kt+ln[A0] Make sure to plug in molarity. Everything is about molarity! Also make sure to convert minutes to seconds in this scenario because the units of k are in seconds. The answer is .217
The decomposition of a 0.250 M sample of NO2 to oxygen gas and nitrogen gas at 550. K has k = 0.312 M-1 hr-1. How many hours are required for 18.2% of the NO2 to decompose? Enter your response to the nearest 0.01 hr.
The units of the rate constant indicate a second order reaction. Thus the formula to use is 1/[A(t)]= kt + 1/[A] However, you must first calculate how much 81.8% of 0.25 is first to plug into the equation to then solve for t. The answer is 2.85 Note: The (t) isn't actually plugged in
collision theory
Theory that describes chemical reactions as occurring when reactants collide with sufficient energy and in the correct orientation. Reactants must collide to react, they just wont always react when colliding.
What do catalysts effect?
They effect the overall mechanism of the reaction but not the net energy difference or whether the reaction is endothermic or exothermic.
Determine kinetic order by applying the method of initial rates.
This is just where you observe experimental trials and pick two best ones to solve for k.
Calculate activation energy and/or the value of the rate constant at various temperatures by application of the Arrhenius equation.
Two main equation: k=Ae^-Ea/RT ln(k2/k1)=-Ea/R(1/T2-1/T1)
Determine equilibrium expressions (reaction quotients) and equilibrium constants.
Use equilibrium rules to rewrite reactions as product concentrations or pressures to the power of coefficients divided by reactant concentrations or pressures to the power of coefficient's aA+bB---->cC+dD equilibrium constant= [C]^c[D]^d/[A]^a[B]^b
Determine the average rate of change of B from 𝑡=0 seconds to 𝑡=392 seconds. A⟶2B The concentration of [A] to time (0, 0.650) (392, 0.180)
Use the coordinates to find the value of the average rate by doing y2-y1/x2-x1. Then multiply that by 2 to get the production of B.
Calculate the activation energy for a reaction if the rate constant k doubles when the temperature increases from 295 K to 305 K. Enter your response in kilojoules per mole (kJ/mol) to the nearest 0.1 kJ/mol.
Use the formula where ln (k2/k1)=-Ea/R(1/t2-1/t1) The answer is 51.9
Determine the units of a rate constant for any kinetic order by algebraic manipulation of the (differential) rate law.
Use the rate law and multiply the reactants. Then take the reactants and move them to the left side of the equation where rate lies to solve for k. The units of the reaction rate are typically given. Then use exponent rules to determine units.
integrated rate law
Version of the rate law that allows for the calculation of changes on reactant concentration over time and for graphical determination of the rate constant.
Le Châtelier's principle
When a stress is applied to a system at equilibrium, the reaction shifts in a direction to relieve that stress.
What are Chatiliers tenants?
When you increase temp of a endothermic reaction, you will get more products. When you decrease temp on a endothermic reaction, you will get more reactants. When you increase temp of an exothermic reaction you will get more reactants. When you increase the concentration of a reactant, you will get more products. When you increase the concentration of a product, you will get more reactants.
Is chemical equilibria and dynamic equilibria the same?
Yes
What do you do if the Kp value is asked but they only give you moles of each reactant?
You must convert the moles into a molar ratio and then multiply by the total pressure of the system.
When making an ICE table, and the concentrations of reactants and products are given as well as the equilibrium constant, how do you calculate the concentrations of each reactant at equilibrium?
You plug in the initial concentrations plus the change values in the ICE table into the equilibrium constant formula. Make sure to square the initial concentration + change if the equilibrium constant formula dictates as such. Then set that equal to the given K value and solve for X and then plug that back into the ICE table to solve for equilibrium.
dentify the correct equilibrium equation for the chemical reaction below. 3 Fe(s) + 4 H2O(g) ⇄ Fe3O4(s) + 4 H2(g)
[H2]^4/[H2O]^4 Solids and liquids are not included in equilibrium
bimolecular
an elementary step in a reaction that involves two particles, either the same species or different, that collide and go on to form products
What are the units of the equilibrium constant?
no units
unimolecular
one reactant molecule
The mechanism for the reaction of nitrogen dioxide with carbon monoxide to form nitric oxide and carbon dioxide is thought to be the following. NO2 + NO2 ⇄ NO3 + NO (fast) NO3 + CO → NO2 + CO2 (slow) What is the rate law expected for this mechanism?
rate=[NO2]^2[CO]/[NO]
Differential rate law
rate=k[A]^m[B]^n where A and B are reactants
What is not included in the equilibrium constant?
solids and liquids
molecularity
the number of molecules that participate as reactants in an elementary reaction
rate-determining step
the slowest step in a reaction mechanism
Which of the following are factors effecting the rate of a reaction? 1) Catalysts 2) Temperature 3) Nature of Reactant 4) Concentration 5) Reactant particle size
ALL
Arrhenius equation
An equation relating the rate constant, activation energy, frequency of collisions, orientation, and temperature.
heterogeneous equilibrium
An equilibrium in which the species are in different phases.
elementary step
An individual molecular event with a transition state and rate law, typically part of a series that makes up a reaction mechanism.
What is the primary difference between instantaneous rate and average rate?
Average rates are over a finite period of time while instantaneous rates are for one specific point in time.
According to le Chatiliers principle, what will be favored in the following scenarios? 1) Increasing temp. of a endothermic reaction? 2) Increasing temp. of a exothermic reaction? 3) Increasing concentration of reactants? 4) Decreasing concentration of reactants? 5) Increasing concentration of products? 6) Decreasing concentration of products? 7) Increasing volume? 8) Increasing pressure?
1) More products 2) More reactants 3) More products 4) More reactants 5) More reactants 6) More products 7) Favored to side with more moles 8) Favored to side with less moles
What do the following values of the equilibrium constant represent? 1) K=1 2) K>1 3) K<1
1) There are an equal amount of reactants and products at equilibrium 2) There are more products than reactants at equilibrium 3) There are more reactants than products at equilibrium Why? Because the rate constant is products/reactants
A student is studying the iron(III)-thiocyanate equilibrium by mixing equal amounts of 0.10 M Fe(NO3)3 and 0.10 M KSCN, along with some distilled water, into three separate containers. Then, to each container, he mixes in one of the following reagents. Fe3+(aq)+SCN−(aq)↽−−⇀Fe(SCN)2+(aq) Determine how the equilibrium will be affected by the addition of each reagent. 1)Adding 0.10 M Fe(NO3)3 will shift the equilibrium 2)Adding 0.10 M KSCN will shift the equilibrium 3)Adding 0.10 M NaOH will shift the equilibrium
1) more reactant means the equilibrium will shift right 2) more reactant means the equilibrium will shift right 3) NaOH will decrease the amount of products so the reaction will make more products to stay in equilibrium so it will shift left
Select the true statements regarding energy changes during a reaction. 1)Reactants must collide with proper orientation and with energy greater than or equal to the activation energy for a reaction to occur. 2)When the activation energy is high, the reaction rate is fast. 3)Decreasing the temperature decreases the kinetic energy of the reactants, and the reaction goes more slowly. 4)The energy of a collision between atoms or molecules must be greater than or equal to the activation energy, 𝐸a�a, for bonds to be broken. 5)If the heat of reaction, Δ𝐻Δ, is negative, the energy of the products is higher than the energy of the reactants and the reaction is exothermic. 6)The activation energy, 𝐸a, of the forward reaction is the difference between the energy of the products and the energy of the transition state. 7)Increasing the concentration of reactants increases the number of collisions, and the reaction goes faster.
1,3,4,7
2O3--> 3O2 What equation relates the consumption of O3 to the production of O2?
1/-2O3=1/3O2
catalyst
A substance that provides an alternate, lower-energy path for a reaction to occur but is not consumed by the reaction.
ICE table
A table that shows the initial, change, and equilibrium values of the species in an equilibrium.
first order
A type of reaction in which the rate depends upon a reactant's concentration raised to the first power.
second order
A type of reaction in which the rate depends upon a reactant's concentration raised to the second power.
What is the overall reaction corresponding to the mechanism below? A + B → AB C + D → CD
A+B+C+D---->AB+CD
frequency factor
A. Indicates the number of correctly oriented reactions per unit time.
Derive and explain half-life using integrated rate laws.
Be able to define half life which is the amount of time it takes for a substance to decompose into half of its original concentration. Also be able to use the integrated rate laws to determine k, half life, or the initial concentration. First order half life= ln(2)/k First order half life equation that tells the percentage of a reactant LEFT after a certain amount of time= (-k)(t). Then put that to the power of e to get the percentage left. Second order half life= 1/k[A0] Zero order half life equation= [A0]/2k
Why are termolecular reactions rare?
Because according to collision theory there is extremely low probability of more than two particles colliding at the same time with sufficient energy and in the correct orientation.
Describe activation energy and the transition state through exploration of collision theory.
Collision theory states that reactants must collide with both the correct orientation and correct amount of energy (more that activation energy) to react. In the Arrhenius equation, k=Ae^-Ea/RT. A represents the rate of collisions and which fraction of collisions occur with proper orientation. e^-Ea/RT represents the fraction of collisions that occur with proper energy. The transition state refers to the peak of a reaction curve at which reactants are beginning to turn into products so both species are present. Activation energy is simply the energy required for a reaction to take place.
What does increasing the surface area of a reactant do?
Collision theory; increases reaction rate which is why solids and liquids are considered in reaction rates.
Which variables does the differential rate law relate?
Concentration and reaction rate REMEBER THE LAW AND ITS COMPONENTS
Identify the intermediate(s) in the reaction mechanism below. A + B → C + D A + D → C
D
Consider this energy profile for a chemical reaction. Determine the relative magnitudes of the forward and reverse rate constants. The energy profile showed a exothermic reaction. 𝑘forward=𝑘reverse kforward=kreverse 𝑘forward<𝑘reverse kforward<kreverse 𝑘forward>𝑘reverse kforward>kreverse What can you infer about the equilibrium constant? 𝐾>1 K>1 𝐾=1 K=1 𝐾<1
Exothermic reactions are more favored to react to the right because to go from products to reactants require a lot of energy. Thus, the reaction favors the right. Then you know that kforward>kreverse and you also know that k>1 because a large value of k represents a reaction favored for more products.
Use kinetic order to predict changes in reaction rate as a result of changes in reactant concentration.
If the rate order is 1, then the relationship between concentration and reaction rate is linear. For example, if you half the concentration of a first order reactant, then the reaction rate will also half. If the rate order is 0, then there is no change in reaction rate even if you change the concentration of the zero order reactant. If the rate order is 2, then the relationship between concentration and reaction rate is squared. If you change multiple concentrations of different rate order reactants, multiply the times of how much faster/slower the reaction occurs of each individual reactant change together not including zero.
How can one determine whether a step is the rate determining step in a reaction mechanism?
If the step had more bonds that need to be broken than any other step, it is most likely the rate determining step. This is due to the fact that bond breaking is endothermic and requires an input of energy which directly relates to activation energy. The higher the number of bonds that need to be broken, the higher the Ea. The higher the activation energy, the slower the reaction
rate
In a chemical reaction, the change in the concentration of a reactant or product per unit time.
What can you do whilst writing equilibrium constants that you can not do while writing reaction rates.
In equilibrium constants, the coefficient represents the coefficient of the reactant/product. In rate laws and rates, the exponent refers to the rate order which DOES NOT equal to the coefficient of the species.
The mechanism for the reaction of nitrogen dioxide with carbon monoxide to form nitric oxide and carbon dioxide is thought to involve the following elementary steps. NO2 + NO2 → NO3 + NO NO3 + CO → NO2 + CO2 It has not yet been determined which step is fast and which is slow. Which of the following interventions would enable you to conclusively determine the relative speeds of the two steps? Select all interventions that would be expected to give different results given the two possibilities for the relative speeds of the steps. Increase the concentration of NO2 Decrease the concentration of NO2 Increase the concentration of NO Increase the concentration of CO Decrease the concentration of NO Decrease the concentration of CO Decrease the concentration of NO3 Increase the concentration of NO3
Increasing and decreasing the concentrations of NO and CO because you simply write the rate law of both reactions considering each to be the rate determining reaction. Then you compare the two rate laws and the reactants with changing exponents/rate orders are the ones you can change concentrations of to observe which is the actual rate determining step.
