chm 1046 test 2. ch 12 and 13

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Consider the following equilibrium process between dinitrogen tetrafluoride (N2F4) and nitrogen difluoride (NF2): N2F4(g) <--> 2NF2(g) ΔH° = 38.5 kJ/mol Predict the changes in the equilibrium and K if: the reacting mixture is heated at constant volume.

(heat added to rxtnts) Reaction shifts right, generates more product and increase K.

What order is Ms^-1?

Important Heterogenous reactions

1. Fischer-Tropsch chemistry 2. Fluidized catalytic cracking 3. Automotive three-way catalysis 4. Haber-Bosch process 5.

The proposed mechanism must meet four criteria:

1. The elementary steps must add up to the overall balanced equation. 2. The mechanism must correlate with the experimentally established rate law. 3. The elementary steps must be physically and chemically reasonable. 4. The mechanism should be as simple as possible while still agreeing with experiment.

2 SO3(g) <--> 2 SO2(g) + O2(g) Pi(SO3) = 0.115 atm, Pi(SO2) = 1.05 atm, Pi(O2) = 1.20 atm, Kp = 6.0 atm What is the reaction quotient? What direction will the reaction shift to?

100 left

In an experiment, a sample of NaClO3 was 90% decomposed in 44 min. The rate of this reaction doubles for every 10°C rise in temperature. Approximately how long (in min) would this decomposition have taken if the sample had been heated 20°C higher?

11 min

how many reactions will 4A + 2B have?

R =

8.314 J/K*mol gas constant

A catalyst causes a reaction to reach equilibrium more quickly. It does not change the equilibrium concentration or K.

Consider this reaction at equilibrium: 2SO2(g) + O2(g) <--> 2SO3(g), delta Hºrxn = -198 kJ/mol If the volume of the system is compressed at constant temperature, what change will occur in the position of the equilibrium? A) A shift to produce more SO3 B) No change C) A shift to produce more O2 D) A shift to produce more SO2

A. A shift to produce more SO3

Which reaction most favors the formation of products? A. K = 1x10^22 B. K = 5X10^-31 C. K= 1X10^-13 D. K= 4.7X10^-4

A. K = 1x10^22

Quadrupling the concentration of a reactant increases the rate of a reaction four times. With this knowledge, answer the following questions. What is the order of the reaction with respect to that reactant? A. zero B. first C. second D. third

B. First

Given the following information: 2A(g) + B(g) <--> A2B(g) Kp1 2A(g) + C2(g) <--> 2AC(g) Kp2 3/2 A2 + B(g) + C(g) <--> AC(g) + A2B(g) Kp3 Which relationship represents the equilibrium constant for the reaction: 4A(g) + C2(g) + A2B(g) <--> 3A2(g) + B(g) + 2C(g) A) Knet = Kp1 x Kp2 x Kp3^2 B) Knet = Kp1 x Kp2/ Kp3^2 C) Knet = Kp1 x Kp2/ Kp3 D) Knet = Kp1 x Kp2 x 2 Kp3 E) Knet = Kp1 x Kp2 x Kp3

B. Knet = Kp1 x Kp2/ Kp3^2

Concerning the rate law, Rate = k[A][B][C], what are appropriate units for the rate constant k? A) M-1s-1 B) M-2s-1 C) s-1 D) M2/s E) M/s

B. M-2s-1

= 1Which relationship is true for the following chemical reaction at time 1? A <--> B ** LOOK AT REC #6 Q 15 FOR GRAPH A) At t = 1, Q = K B) This reaction proceeds in the reverse direction to reach equilibrium C) At t = 1, Q < K D) This reaction is currently in equilibrium at t = 1 E) This reaction is irreversible, so the reaction will proceed only in the forward reaction.

C. At t = 1, Q < K

A proposed mechanism for the following reaction is shown below. Identify the catalyst in the reaction. 2H2O2(aq) → 2H2O(aq) + O2 in the presence of I- (aq) Step 1: H2O2(aq) + I- (aq) → H2O(l) + OI- (aq) (slow) Step 2: H2O2(aq) + OI- (aq) → H2O(l) + O2(g) + I- (aq) (fast) A) H2O2 B) OI- C) I- D) H2O E) O2

C. I-

Powdered manganese(IV) oxide, MnO2(s), increases the rate of the decomposition reaction of hydrogen peroxide, H2O2(aq). Which statements about MnO2 are correct? I. The rate is independent of the particle size of MnO2. II. MnO2 provides an alternative reaction pathway for the decomposition with a lower activation energy. III. All the MnO2 is present after the decomposition of the hydrogen peroxide is complete. A. I and II only B. I and III only C. II and III only D. I, II and III

C. II and III only

The reaction 2SO3(g) <--> 2SO2(g) + O2(g) is endothermic. If the temperature is increased, A) the pressure will decrease. B) more SO3 will be produced. C) Kc will increase. D) no change will occur in Kc E) Kc will decrease

C. Kc will increase.

Consider the two gaseous equilibria: SO2 (g) + 1/2O2 (g) <--> SO3 (g) K1 2SO3 (g) <--> SO2 (g) + O2 (g) K2 The values of the equilibrium constants K1 and K2 are related by A) K2^2 = K1 B) K2 = K1^2 C) none of these. D) K2 = 1/K1^2 E) K2 = 1/K1

D. K2 = 1/K1^2

Given the following data for this reaction: NH4+(aq) + NO2-(aq) --> N2(g) + 2H2O(l) EXPT #1 [NH4+]= 0.010 M [NO2-]= 0.020 M RATE= 0.020 M/s EXPT #2 [NH4+]= 0.015 M [NO2-]= 0.020 M RATE= 0.030 M/s EXPT #3 [NH4+]= 0.010 M [NO2-]= 0.010 M RATE= 0.005 M/s The rate law for the reaction is: A) Rate = k[NH4+][NO2-] B) Rate = k[NH4+]^2[NO2-]^2 C) Rate = k[NH4+]^2[NO2-] D) Rate = k[NH4+][NO2-]^2 E) none of the above

D. Rate = k[NH4+][NO2-]^2

When the following reaction is at equilibrium, which of these relationships is always true? 2NOCl(g) <--> 2NO(g) + Cl2(g) A) 2[NO] = [Cl2] B) [NO] [Cl2] = [NOCl] C) [NOCl] = [NO] D) [NO]^2 [Cl2] = Kc[NOCl]^2 E) [NO]^2 [Cl2] = [NOCl]^2

D. [NO]^2 [Cl2] = Kc[NOCl]^2

Fluidized catalytic cracking

High MW petroleum → low MW fuels, like gasoline Zeolite catalysts, high temperature combustor In your fuel tank!

T =

K , absolute temp

write the concen equation for the rxn: CH3COOH (aq) + H2O (l) <--> CH3COO- (aq) + H3O+ (aq)`

Kc = ([CH3COO-][H3O+]) / [CH3COOH] H2O is not included bc it is a liquid

Concentration can be expressed as ___ or _____

M or atm

Haber-Bosch process

N2 + H2 → NH3

Haber-Bosch Reaction

N2(g) + 3H2(g) --> 2NH3(g)

transition state

a high-energy intermediate state of the reactants during a chemical reaction that must be achieved for the reaction to proceed

Catalyst definition

a substance that increases the rate of a chemical reaction without being consumed.

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if N2 is removed? If N2 is removed, [N2] ____ , [O2] ____ , and [NO] ____

decreases, increases, decreases

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if more O2 is added? If more O2 is added, [N2] ____ , [O2] ____ , and [NO] ___

decreases, increases, increases

The reaction of CO with Cl2 gives phosgene (COCl2), a nerve gas that was used in World War I. Use the mechanism shown here to complete the following exercises. Cl2(g) <--> 2 Cl(g) (fast, k1 represents the forward rate constant, k−1 the reverse rate constant) CO(g) + Cl(g) → COCl(g) (slow, with k2 its rate constant) COCl(g) + Cl(g) → COCl2(g) (fast, with k3 its rate constant) Write the rate law for each elementary reaction: reaction 1, reverse

rate = k-1 * [Cl]^2

Reaction order is "always" defined in terms of ____ concentrations.

reactant

A(g) + B(g) <--> C(g) increase volume shifts ____

to the side with most moles gas, LEFT

Changes in V or P will cause equilibrium to shift if delta n gas ____.

≠ 0

Which give HETEROgeneous equilibria? (Select all that apply.) A. 2 MnO2(s) + 2 H2SO4(aq) <--> 2 MnSO4(s) + 2 H2O(g) + O2(g) B. SO2(g) + Cl2(g) <--> SO2Cl2(g) C. 2 SO2(g) + O2(g) <--> 2 SO3(g) D. CS2(g) + 3 O2(g) <--> CO2(g) + 2 SO2(g) E. C(s) + CO2(g) <--> 2 CO(g) F. H2O2(l) <--> H2(g) + O2(g) G. S8(g) <--> 8 S(g) H. 2 Pb(NO3)2(s) <--> 2 PbO(s) + 4 NO2(g) + O2(g)

**must have different stages ( ). A. 2 MnO2(s) + 2 H2SO4(aq) <--> 2 MnSO4(s) + 2 H2O(g) + O2(g) E. C(s) + CO2(g) <--> 2 CO(g) F. H2O2(l) <--> H2(g) + O2(g) H. 2 Pb(NO3)2(s) <--> 2 PbO(s) + 4 NO2(g) + O2(g)

Which of the systems described below give HOMOgeneous equilibria?(Select all that apply.) A. 2 MnO2(s) + 2 H2SO4(aq) <--> 2 MnSO4(s) + 2 H2O(g) + O2(g) B. SO2(g) + Cl2(g) <-->SO2Cl2(g) C. 2 SO2(g) + O2(g) <--> 2 SO3(g) D. CS2(g) + 3 O2(g) <--> CO2(g) + 2 SO2(g) E. C(s) + CO2(g) <--> 2 CO(g) F. H2O2(l) <--> H2(g) + O2(g) G. S8(g) <--> 8 S(g) H. 2 Pb(NO3)2(s) <--> 2 PbO(s) + 4 NO2(g) + O2(g)

**must have same stages ( ). B. SO2(g) + Cl2(g) <-->SO2Cl2(g) C. 2 SO2(g) + O2(g) <--> 2 SO3(g) D. CS2(g) + 3 O2(g) <--> CO2(g) + 2 SO2(g) G. S8(g) <--> 8 S(g)

Haber-Bosch process: N2(g) + 3H2(g) <--> 2NH3(g) Delta H°rxn = -91.8 kJ You are tasked with feeding 7.3 billion people. NH3 is crucial to increasing food production by maximizing crop yield. How do you shift the equilibrium to favor products?

- Decrease the temperature. - Increase the pressure. - Decrease [NH3] by removing NH3 as it forms. - Add more H2 and N2 as its consumed.

heterogeneous catalyst through what 3 things?

- shape selection - acidity/basicity - incorporation of metal particles

reaction rate equation

-(change in concentration/change in time)

2 NO(g) + Cl2(g) <--> 2 NOCl(g) Pi(NO) = 1.05 atm, Pi(Cl2) = 1.05 atm, Pi(NOCl) = 0 atm, Kp = 2.1 ✕ 103 What is the reaction quotient? What direction will the reaction shift to?

0 right

2 NH3(g) <--> N2(g) + 3 H2(g) [NH3]i = 0.435 M, [N2]i = 0.165 M, [H2]i = 0.110 M Kc = 16 What is the reaction quotient? What direction will the reaction shift to?

0.00116 right

At a temperature of 65°C, the vapor pressure of water is 0.247 atm. H2O(l) <--> H2O(g) What is the value of the equilibrium constant Kp for the transformation at 65°C?

0.247 Kc= [H2O] (l) is not included so Kc=0.247 M and atm are = delta n = 0, so RT = 1 so Kp and Kc = 0.247

0.43

What order is s^-1?

factors that affect reaction rates

1. Physical state of the reactants 2. Reactant concentrations 3. Reaction temperature 4. Presence of a catalyst 5. Nature of the reacting species (Fe vs Na)

Rate Equation 4 points:

1. determined experimentally 2. gives you rate constant 3. tells you how rate changes with concentration change. 4. only describes reactants.

Rate Expression 4 points

1. determined from the chemical equation 2. tells you how concentrations change relative to each other over time 3. describes both reactants and products. 4. Rate is concentration dependent.

3 things in the Collision theory of reaction rates

1. molecules must collide 2. have enough energy to make and break bonds 3. have the correct orientation to react

How will the rate of the following reaction change when the concentration changes by: 2NO (g) + O2 (g) --> 2NO2 (g) Rate= k[NO]^2 [O2] If NO is halved, the rate:

1/4 the rate rate = [1]^2 [1]= 1 rate = [0.5]^2 [1]= 0.25

**** LOOK AT REC #5 Q 17 FOR GRAPH

17) C. * at top of hump

**** LOOK AT REC #5 Q 18 FOR GRAPH

18) B

# of half-lives = 1 [A] = [A]0/n = ?

What order is M^-1 s^-1

2 SO3(g) <--> 2 SO2(g) + O2(g) [SO3]i = 2.25 M, [SO2]i = 2.25 M, [O2]i = 2.25 M, Kc = 0.22 What is the reaction quotient? What direction will the reaction shift to?

2.25 left

Consider the following reaction in aqueous solution. 5 Br−(aq) + BrO3−(aq) + 6 H +(aq) → 3 Br2(aq) + 3 H2O(l) If the rate of disappearance of Br−(aq) at a particular moment during the reaction is 4.2 ✕ 10−4 M·s−1, what is the rate of appearance (in M·s−1) of Br2(aq) at that moment?

2.5e-4 M*s^-1

2 NH3(g) <--> N2(g) + 3 H2(g) Pi(NH3) = 2.15 atm, Pi(N2) = 10.40 atm, Pi(H2) = 10.40 atm, Kp = 6.8 ✕ 104 What is the reaction quotient? What direction will the reaction shift to?

2.5e3 right

The decomposition of ethane (C2H6) to methyl radicals is a first-order reaction with a rate constant of 5.36 × 10−4 s−1 at 700°C: C2H6 (g) --> 2CH3 (g) Calculate the half-life of the reaction in minutes.

21.5 min t 1/2= 0.693 / k = 0.693/5.36x10^-4s^-1 = 1.29 x 10^3 s * (1 min / 60s) = 21.5 min

# of half-lives =? [A] = [A]0/n = 8

What order is M^-2 s^-1

# of half-lives = 2 [A] = [A]0/n =

# of half-lives = ? [A] = [A]0/n = 16

how many reactions will 2A + 2B have?

N2(g) + O2(g) <--> 2 NO(g) [N2]i = 0.125 M, [O2]i = 0.250 M, [NO]i = 1.25 M, Kc = 0.049 What is the reaction quotient? What direction will the reaction shift to?

50 left

how many reactions will 3A + 2B have?

Hydrogen reacts with nitrogen monoxide to form dinitrogen monoxide (laughing gas) according to the following equation. H2(g) + 2 NO(g) → N2O(g) + H2O(g) [NO] (M) = 0.27 , 0.54, 0.54 [H2] (M) = 0.32, 0.32, 0.64 Rate (mol/L/s)= 2.100 ✕ 10^−3, 8.398 ✕ 10^−3, 1.680 ✕ 10^−2 Determine the rate constant (in mol−2·L2·s−1) using data from the first column.

9.0 e-2

write the elementary rxn and rate law for a unimolecular rxn.

A --> products rate= k[A]

write the elementary rxn and rate law for a Termolecular rxn.

A+ A +A --> products A+ A + B --> products A+ B + C --> products rate= k[A]^3 rate= k[A]^2[B] rate= k[A][B][C]

write the elementary rxn and rate law for a bimolecular rxn.

A+ A --> products A+ B --> products rate= k[A]^2 rate= k[A][B]

For the reaction X + Y --- Z, the reaction rate is found to depend only upon the concentration (M) of X. A plot of 1/X verses time gives a straight line. The equation of this line is y= 0.08x + 2. 1/[X] line starts at 2, at 50 seconds, line is at about 6 *****LOOK AT REC #5 Q 8 for graph What is the initial concentration of X and the rate constant k respectively? A) 0.5 M, 0.08 s-1M-1 B) ln(0.08) M, 2 s-1M-1 C) 2 M, 12.5 s-1M-1 D) 0.16 M, 0.5 s-1M-1

A. 0.5 M, 0.08 s-1M-1

The half life for a first order reaction is 27 min. How long will it take for 4 half lives to occur? A) 108 min B) Not enough information given C) 81 min D) 260 min E) 53,000 mi

A. 108 min

In which of these gas-phase equilibria is the yield of products increased by increasing the total pressure on the reaction mixture? A) 2NO(g) + Cl2(g) <--> 2NOCl(g) B) PCl5(g) <--> PCl3(g) + Cl2(g) C) CO(g) + H2O(g) <--> CO2(g) + H2(g) D) 2SO3(g) <--> 2SO2(g) + O2(g) E) H2(g) + I2(g) <--> 2HI(g)

A. 2NO(g) + Cl2(g) <--> 2NOCl(g)

For the following reaction at equilibrium in a reaction vessel, which change will cause the reaction to become yellow? CrO4^2- (yellow) (aq) + 2H+ (aq) Cr2O7^2- (orange) + H2O (l) A) Adding NaOH which participates in an acid-base reaction B) Removing water from the reaction vessel as it is formed C) Increasing the H+ concentration in the reaction vessel D) Adding the salt K2CrO4 to the reaction vessel

A. Adding NaOH which participates in an acid-base reaction

This figure represents the Haber-Bosch process for the production of ammonia, N2 (g) + 3H2 (g) <--> 2NH3 (g) delta Hºrxn = -91.8 kJ/mol. Which of the following DOES NOT occur during this synthesis **** LOOK AT REC #6 Q 10 FOR GRAPH A) Increasing the temperature of the of the reaction vessel after ammonia is formed B) Increasing the pressure of the reaction chamber for the reactants N2 and H2 gas C) Removing the product ammonia from the reaction chamber D) Adding more reactants N2 and H2 gas as it is consumed E) Adding a catalyst to increase the rate of product formation

A. Increasing the temperature of the of the reaction vessel after ammonia is formed

1) The rate law for the reaction 2NO2 + O3 --- N2O5 + O2 is rate = k[NO2][O3]. Which one of the following mechanisms is consistent with this rate law? A) NO2 + O3 --- NO3 + O2 (slow) NO3 + NO2 --- N2O5 (fast) B) NO2 + NO2 --- N2O2 + O2 (slow) N2O2 + O3 --- N2O5 (fast) C) NO2 + NO2 --- N2O4 (fast) N2O4 + O3 --- N2O5 + O2 (slow) D) NO2 + O3 --- NO5 (fast) NO5 + NO5 --- N2O5 + 5/2O2 (slow)

A. NO2 + O3 --- NO3 + O2 (slow) NO3 + NO2 --- N2O5 (fast)

How will decreasing the volume affect the equilibrium in each of the following reaction? SO2(g) + H2O(l) ↔ H2SO3(aq) A) Shift Left B) Stay the same C) Shift right

A. Shift left

For the reaction X + Y --> Z, the reaction rate is found to depend only upon the concentration of X. A plot of 1/X verses time gives a straight line. ******* LOOK AT REC 2/13 Q 4 FOR GRAPH What is the rate law for this reaction? A) rate = k [X]^2 B) rate = k [X][Y] C) rate = k [X] D) rate = k [X]^2[Y]

A. rate = k [X]^2

How will the addition of a catalyst affect the equilibrium A) Shift Left B) Stay the same C) Shift right 2SO2(g) + O2(g) ↔ 2 SO3(g)

B) Stay the same

How will the addition of a catalyst affect the equilibrium CO(g) + H2O(g) ↔ CO2(g) + H2(g) A) Shift Left B) Stay the same C) Shift right

B) Stay the same

Ozone decomposes to oxygen according to the equation 2 O3(g) → 3 O2(g). Write the equation that relates the rate expressions for this reaction in terms of the disappearance of O3 and the formation of oxygen. A. − 1/3 * (Δ[O3] /Δt) = 1/2 * (Δ[O2] / Δt) B. -1/2 * ( Δ[O3] / Δt) = 1/3 (Δ[O2] / Δt) C. -2/3 * ( Δ[O3] / Δt) = (Δ[O2] / Δt) D. -1/2 * ( Δ[O2] / Δt) = (Δ[O3] / Δt)

B. -1/2 * ( Δ[O3] / Δt) = 1/3 (Δ[O2] / Δt)

The data below refer to the following reaction: 2NO(g) + Br2(g) <--> 2NOBr(g) Concen (M) initial of [NO] = 2.5 Concen (M) initial of [Br2] = 5.0 Concen (M) initial of [NOBr] = 1.0 Concen (M) equilibrium of [NO] = 2.0 Concen (M) equilibrium of [Br2] = - Concen (M) equilibrium of [NOBr] = - Calculate Kc. A) 0.10 B) 0.12 C) 0.14 D) 0.080 E) None of the above

B. 0.12

The solubility of silver chloride can be increased by dissolving it in a solution containing ammonia. AgCl (s) <--> Ag+ (aq) + Cl- (aq) K1 = 1.6 x 10-10 Ag- (aq) + 2NH3 (aq) Ag(NH3)2+ (aq) K2 = 1.5 x 10^7 What is the value of the equilibrium constant for the overall reaction? AgCl (s) + 2NH3 (aq) <--> Ag(NH3)2+ (aq) + Cl- (aq) Knet = ? A) 3.1 x 10^-3 B) 2.4 x 10^-3 C) 2.3 x 10^14 D) 2.4 x 10^7 E) 1.5 x 10^7

B. 2.4 x 10^-3

Kp for the reaction 4CuO(s) <--> 2Cu2O(s) + O2(g) is 0.49 at 1024 °C. Calculate Kc at this temperature A) 41 B) 4.6 x 10^-3 C) 0.49 D) 5.8 x 10^-3 E) 52

B. 4.6 x 10^-3

which piece of equipment could NOT be used in an experiment to measure the rate of this reaction? CH3COCH3 (aq) + I2 (aq) --> CH3COCH2I (aq) + H+ (aq) + I-(aq) A. A colorimeter B. A gas syringe C. A stopwatch D. A pH meter

B. A gas syringe

If reaction A has an activation energy of 250 kJ and reaction B has an activation energy of 100 kJ, which of the following statements must be correct? A) If reaction A is exothermic and reaction B is endothermic then reaction A is favored kinetically. B) At the same temperature the rate of reaction B is greater than the rate of reaction A. C) The energy of reaction A must be greater than the energy of reaction B. D) The energy of reaction B must be greater than the energy of reaction A. E) The rate of reaction A at 25 degrees C equals the rate of reaction B at 100 degrees C.

B. At the same temperature the rate of reaction B is greater than the rate of reaction A.

HCl is reacted w large pieces of Calcium carbonate, the rxn is then repeated using calcium carbonate powder. How does this change affect the Ea and the collision frequency? A. Ea= increases , collision frequency = increases B. Ea= stays constant, collision frequency = increases C. Ea= increases , collision frequency = stays constant D. Ea= stays constant, collision frequency = stays constant

B. Ea = stays constant Collision Frequency = increases

The peroxodisulfate ion can oxidize iodide ions to iodine according to the balanced equation S2O82- + 2I - --- 2SO42- + I2. The reaction is catalyzed by certain chemical species. Identify the catalyst in the following mechanism: step 1: Fe3+ + 2I - --- Fe2+ + I2 step 2: S2O82- + Fe2+ --- 2SO42- + Fe3+ A) S2O82- B) Fe3+ C) SO42- D) I - E) Fe2+

B. Fe3+ (molecule found in both reactants step 1 and products step 2)

Which statements describe the action of catalyst? I. It does NOT alter the delta H for a reaction II. It increases the Ea for the reaction III. It alters the mechanism (pathway) for a reaction A. I and II B. I and III C. II and III D. I, II, and III

B. I and III

Which reaction most favors the formation of reactants? A. K = 1x10^22 B. K = 5X10^-31 C. K= 1X10^-13 D. K= 4.7X10^-4

B. K = 5X10^-31

The gas-phase decomposition of nitrous oxide (N2O) is believed to occur via two elementary steps: Step 1: N2O --> N2 + O Step 2: N2O + O --> N2 + O2 Experimentally the rate law is found to be rate = k[N2O]. Identify the intermediate A. N2O B. O C. N2 D. none

B. O

For the following reaction at equilibrium, which gives a change that will shift the position of equilibrium to favor formation of more products? 2NOBr(g) <--> 2NO(g) + Br2(g), delta Hºrxn = 30 kJ/mol A) Add more NO. B) Remove Br2. C) Lower the temperature. D) Increase the total pressure by decreasing the volume. E) Remove NOBr selectively.

B. Remove Br2.

The gas-phase decomposition of nitrous oxide (N2O) is believed to occur via two elementary steps: Step 1: N2O --> N2 + O Step 2: N2O + O --> N2 + O2 Experimentally the rate law is found to be rate = k[N2O]. Which reaction step is faster? A. Step 1. B. Step 2. C. Not enough information

B. Step 2

For the reaction whose rate law is rate = k[X], a plot of which of the following is a straight line? A) ln [X] versus 1/time B) ln [X] versus time C) [X] versus time D) [X] versus 1/time E) 1/[X] versus time

B. ln [X] versus time

For the following reaction at equilibrium, the reactants are colorless while the product is red. The color at equilibrium is orange. What happens when Cl- ions are added to the reaction? (HINT: FeCl3 is insoluble.) Fe^3+ (aq) + SCN- (aq) <--> FeSCN ^2+ (aq) A) the reaction vessel becomes a clear, yellow solution B) the reaction vessel becomes cloudy and more yellow C) the reaction vessel becomes a clear, blood red solution D) the reaction vessel stay the same clear, orange solution

B. the reaction vessel becomes cloudy and more yellow

Build more reactors. Increase the temperature. Add a catalyst.

Which of the following elementary steps is bimolecular? A) A + B + C --- AB + C B) 3B --- B2 + B C) 2A --- A2 D) 2A + B --- A2B E) A2 --- 2A

C. 2A --- A2

The gas-phase decomposition of nitrous oxide (N2O) is believed to occur via two elementary steps: Step 1: N2O --> N2 + O Step 2: N2O + O --> N2 + O2 Experimentally the rate law is found to be rate = k[N2O]. What is the equation for the overall reaction? A. 2N2O + O --> 2N2 + O + O2 B. N2O + O --> N2 + O + O2 C. 2N2O --> 2N2 + O2 D. 2N2O --> 2N2 + O

C. 2N2O --> 2N2 + O2

Concerning the following reaction at equilibrium: 3Fe(s) + 4H2O(g) <--> Fe3O4(s) + 4H2(g), increasing the concentration of the Fe(s) would: A) Shift the equilibrium to the right B) Shift the equilibrium to the left C) Cause no change D) Increase the value of the equilibrium constant, K E) Decrease the value of the equilibrium constant, K

C. Cause no change

At 700 K, the reaction 2SO2(g) + O2(g) <--> 2SO3(g) has the equilibrium constant Kc = 4.3 × 106 , and the following concentrations are present: [SO2] = 0.10 M; [SO3] = 10. M; [O2] = 0.10 M. Which of the following is true based on the above? A) Qc < Kc, the reaction proceeds from right to left to reach equilibrium B) Qc > Kc, the reaction proceeds from right to left to reach equilibrium C) Qc < Kc, the reaction proceeds from left to right to reach equilibrium D) Qc > Kc, the reaction proceeds from left to right to reach equilibrium E) Qc = Kc, the reaction is currently at equilibrium

C. Qc < Kc, the reaction proceeds from left to right to reach equilibrium

Complete the following statement: A catalyst A) increases the average kinetic energy of the reactants. B) increases the collision frequency of reactant molecules. C) alters the reaction mechanism. D) increases the concentration of reactants. E) increases the activation energy.

C. alters the reaction mechanism.

Nitrogen pentoxide decomposes by a first-order process yielding N2O4 and oxygen. 2N2O5 --- 2N2O4 + O2 At a given temperature, the half-life of N2O5 is 0.90 hr. What is the first-order rate constant for N2O5 decomposition? A) [N2O5]/(0.90*2) hr-1 B) 1/ (0.90*[N2O5] ) hr-1 C) ln(2)/0.9 hr-1 D) 0.57 hr-1 E) None of the above

C. ln(2)/0.9 hr-1

The data below were determined for the reaction shown below. S2O8^2- + 3I - (aq) --> 2(SO4)^2- + I3- Exp # : 1 , [S2O8^2-] = 0.038 , [I-] = 0.060 , Initial rate= 1.4 x 10 ^ -5 M/s Exp # : 2 , [S2O8^2-] = 0.076 , [I-] = 0.060 , Initial rate= 2.8 x 10 ^ -5 M/s Exp # : 3 , [S2O8^2-] = 0.076 , [I-] = 0.030 , Initial rate= 1.4 x 10 ^ -5 M/s The rate law for this reaction must be: A) rate = k[S2O8^2-]^2[I -]^2 B) rate = k[S2O8^2- ][I -]^3 C) rate = k[S2O8^2-][I -] D) rate = k[I -] E) rate = k[S2O8^2-]

C. rate = k[S2O8^2-][I -]

Quadrupling the concentration of a reactant increases the rate of a reaction four times. With this knowledge, answer the following questions. Increasing the concentration of a reactant by a factor of three increases the rate of a reaction nine times. What is the order of the reaction with respect to that reactant? A. zero B. first C. second D. third

C. second

The following graph shows the kinetics curves for the reaction of oxygen with hydrogen to form water: O2(g) + 2H2(g) → 2H2O(g). Which curve is hydrogen? LOOK AT RECITATION #5 , Q 16 for graph A) the dashed curve B) the gray curve C) the black curve D) either the gray or the black curve E) any of these curves could be hydrogen

C. the black curve

Fischer-Tropsch chemistry:

CO + H2 → (CH2)n + H2O , syn gas to liquid fuels Fe/Co catalysts Source of fuel for Axis in WWII

Automotive three-way catalysis

CO --> CO2 HC --> CO2 + H2O NOx --> N2

Cl , COCl

Cl2 (g) + CO (g) --> COCl2 (g)

how to "poke" an equilibrium (4 things)

Concentration Pressure Temperature Catalyst

For the reaction BrO3- + 5Br-+ 6H+ --> 3Br2 + 3H2O at a particular time, -delta[BrO3-]/ delta t = 2.2 × 10-2 M/s. What is -delta [Br-]/delta t at the same instant? A) 2.0 × 10-2 M/s B) 24 M/s C) 4.4 × 10-3 M/s D) 1.1 × 10-1 M/s E) 330 M/s

D) 1.1 × 10-1 M/s

At 300 K, the following reaction is found to obey the rate law: Rate = k[NOCl]2: 2NOCl -> 2NO + Cl2 Consider the three postulated mechanisms given below. Then choose the response that lists all those that are possibly correct and no others. Mechanism 1: NOCl → NO + Cl (slow) Cl + NOCl → NOCl2 (fast) NOCl2 + NO → 2NO + Cl2 (fast) Overall: 2NOCl → 2NO + Cl2 Mechanism 2: 2NOCl → NOCl2 + NO (slow) NOCl2 → NO + Cl2 (fast) Overall: 2NOCl 2NO + Cl2 Mechanism 3: NOCl NO + Cl (fast, equilibrium) NOCl + Cl→ NO + Cl2 (slow) Overall: 2NOCl → 2NO + Cl2 A) 2, 3 B) 3 C) 1 D) 2 E) 1, 2

D) 2

The data below refer to the following reaction: 2NO(g) + Br2(g) <--> 2NOBr(g) Concen (M) initial of [NO] = 2.5 Concen (M) initial of [Br2] = 5.0 Concen (M) initial of [NOBr] = 1.0 Concen (M) equilibrium of [NO] = 2.0 Concen (M) equilibrium of [Br2] = - Concen (M) equilibrium of [NOBr] = - Find the concentration of Br2 when the system reaches equilibrium. A) None of the above B) 4.95 M C) 4.15 M D) 4.75 M E) 5.05 M

D) 4.75 M

An experimental drug, D, is known to decompose in the blood stream. Tripling the concentration of the drug increases the decomposition rate by a factor of nine. Write the rate law for decomposition of D. A) The rate law is rate = k[D]^9 B) The rate law is rate = k[D] C) None of the above D) The rate law is rate = k[D]^2 E) The rate law is rate = k[D]^3

D) The rate law is rate = k[D]^2

If the reaction 2X2Z(g) <--> 2X2(g) + Z2(g) is carried out at 1065°C, Kp = 36. Starting from pure X2 introduced into an evacuated vessel at 1065°C, what will the total pressure in the vessel be at equilibrium if the equilibrated mixture contains 2.00 atm of X2(g) and 9.00 atm of Z2 (g)? A) 15.00 atm B) 9.00 atm C) 3.50 atm D) 12.00 atm E) 11.00 atm

D. 12.00 atm

Sodium carbonate and hydrochloric acid react according to the equation below: Na2CO3 (s) + 2HCl (aq) --> CO2 (g) + 2NaCl (aq) + H2O (l) Which conditions will produce the fastest initial rate with 2g of powdered sodium carbonate? A. 100 cm^3 of 1 mol dm^-3 HCl at 323 K B. 50 cm^3 of 2 mol dm^-3 HCl at 323 K C. 100 cm^3 of 1 mol dm^-3 HCl at 348 K D. 50 cm^3 of 2 mol dm^-3 HCl at 348 K

D. 50 cm^3 of 2 mol dm^-3 HCl at 348 K

According to collision theory, A) All collisions result in some sort of chemical reaction B) Molecular orientation alone determines the effectiveness of a collision C) The amount of energy of the particles determines whether a reaction occurs D) Both molecular orientation and amount of energy must be right for a reaction to occur

D. Both molecular orientation and amount of energy must be right for a reaction to occur

The speed of a chemical reaction A) is constant no matter what the temperature is. B) is independent of the amount of contact surface of a solid involved. C) between gases should in all cases be extremely rapid because the average kinetic energy of the molecules is great. D) between ions in aqueous solution is extremely rapid because there are no bonds that need to be broken. E) varies inversely with the absolute temperature

D. between ions in aqueous solution is extremely rapid because there are no bonds that need to be broken.

Which of the following statements about catalysts is false: A) catalysts do not appear in the balanced equation B) catalysts reduce the activation energy for a reaction C) biological catalysts are called enzymes D) catalysts do not alter the mechanism of the reaction and never appear in the rate law E) since catalysts are recycled, even a small amount of catalyst can accelerate a reaction

D. catalysts do not alter the mechanism of the reaction and never appear in the rate law

A correct reaction mechanism for a given reaction usually is: A) the same as its balanced chemical equation. B) obvious if its heat of reaction is known. C) obvious if its reaction order is known. D) sometimes difficult to prove. E) obvious if its activation energy is known.

D. sometimes difficult to prove.

The graphs below all refer to the same reaction. What is the order of this reaction? 1/[A] vs t = curve up [A] vs. t = straight slant down ln[A] vs. t = curve down ******* LOOK AT REC 2/13 Q 6 FOR GRAPH A) first order B) unable to predict C) second order D) zero order

D. zero order

For the following reaction at equilibrium in a reaction vessel, which change will cause the Br2 concentration to DECREASE? 2NOBr(g) <--> 2NO(g) + Br2(g), delta Hºrxn= 30 kJ/mol A) Add a catalyst B) Increase the temperature. C) Add more NOBr. D) Remove some NO. E) Compress the gas mixture into a smaller volume.

E. Compress the gas mixture into a smaller volume.

For the reaction X2 + Y + Z --- XY + XZ, it is found that the rate equation is rate = k [X2][Y]. Why does the concentration of Z have no effect on the rate? A) The fraction of molecules of Z that have very high energies is zero. B) The concentration of Z is very small and the others are very large. C) The activation energy for Z to react is very high. D) Z is an intermediate. E) Z must react in a step after the rate determining step.

E. Z must react in a step after the rate determining step.

For the reaction A + 3B --> 2C, the rate of disappearance of B given by (delta[B]/delta t) may also be expressed as: A) delta[B]/delta t = -delta[A]/delta t. B)delta [B]/delta t = - (1/3)delta[A]/delta t. C)delta [B]/delta t = (1/3) delta[A]/delta t. D)delta [B]/delta t = - 3 delta [A]/delta t. E)delta [B]/ delta t = 3 delta [A]/delta t.

E. delta [B]/ delta t = 3 delta [A]/delta t.

Consider this reaction at equilibrium at a total pressure P1: 2SO2(g) + O2(g) <--> 2SO3(g) Suppose the volume of this system is compressed to one-half its initial volume and then equilibrium is reestablished. The new equilibrium total pressure will be A) unchanged. B) 3.5 P1. C) three times P1. D) twice P1. E) less than twice P1.

E. less than twice P1.

5) With respect to the figure below, which choice correctly identifies all the numbered 5) positions? 1. beginning of graph 2. in ditch (bottom between 2 curves) 3. top of hump 4. end of graph ******LOOK AT REC #5 Q 5 FOR GRAPH A) B B) E C) A D) C E) D

E. row D 1. reactants 2.intermediate 3. activated complex 4. product

Write expressions for the following reversible reactions at equilibrium: 2NO(g) + O2(g) <--> 2NO2(g)

EITHER Kc = [NO2]^2 / ([O2][NO]^2) OR Kp = PNO2^2 / PO2 * PNO2

If you understand the transition state maybe you can use it to lower the ____ / increase ____

Ea , rate

if Energy (products) > Energy (reactants), then it is a ___thermic reaction

Endothermic rxn

if Energy (products) < Energy (reactants), then it is a ___thermic reaction

Exothermic rxn

For a general reversible reaction such as: aA + bB --> cC + dD the equilibrium constant is written as:

K= [products]^m/[reactants]^n = ([C]^c [D]^d)/([A]^a [B]^b)

Write expressions for the following reversible reactions at equilibrium: HF(aq) + H2O(l) <--> H3O+(aq) + F-(aq)

Kc = ([F-][H3O+]) / [HF]

Write expressions for the following reversible reactions at equilibrium: CH3COOH(aq) + C2H5OH(aq) <--> CH3COOC2H5(aq) + H2O(l)

Kc = [CH3COOC2H5] / ([CH3COOH] [C2H5OH])

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ Write the expression for the equilibrium constant (Kc) for this reversible reaction.

Kc = [NO]^2 /[N2][O2]

For a titration to be effective, the reaction must be rapid and the yield of the reaction must essentially be 100%. Is Kc > 1, < 1, or ≈ 1 for a titration reaction?

Kc is the product of all reaction products DIVIDED BY the product of the reactants, with all concentrations of reactants and products raised to their respective stoichiometric powers. As the titration proceeds, the amount of reactants DECREASES , and the amount of products INCREASES. Because the value of the numerator is MUCH GREATER THAN the value of the denominator, the value of Kc will be MUCH GREATER THAN 1 for an effective titration reaction.

heterogeneous catalyst properties

Multiphase (Mostly solid-liquid and solid-gas) High temperature

If the concentrations of products and reactants are equal, is the system at equilibrium?

NO , equal concentrations of products and reactants DOES NOT guarantee that the rate of the forward reaction is EQUAL TO the rate of the reverse reaction, which defines a system being at equilibrium.

if you know K, then you can do what 3 things?

Predict the direction in which a reaction mixture will proceed to reach equilibrium. Calculate the concentration of reactants and products once equilibrium has been reached. Predict if and which direction the equilibrium will shift upon perturbation.

Reaction shifts left, generates more reactants and K stays the same.

Reaction shifts right, generates more products and K stays the same. Pressure decrease = volume increase

homogeneous catalyst properties

Single phase (Typically liquid) Low temperature

Le Chatelier's Principle

States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.

What does a catalyst do?

Takes part in the reaction (interacts with the reactants). Lowers Ea by changing the mechanism by which the process occurs. After the interaction it returns to its original state (is not consumed). Speeds up both the forward and the reverse reactions. Does not increase the yield of the product, but gets to the product more quickly.

Molecules must collide info

The number of collisions is proportional to the number of molecules, that are able to collide. CONCEN DEPENDENT 2[A] = 2 x collisions = 2 x rate

The reaction rate increases with temperature because:

The particles collide more frequently. More particles possess enough energy to overcome the activation energy and react.

Chemical Equilibrium

The rates of the forward and reverse reactions are equal. a chemical change is occurring (intramolecular bonds broken/formed) concentrations of the reactants and products remain constant. this does not mean [conc] of reactants and products are equal!

A <--> B means that

The system is "closed"—no substance can enter or leave The system is dynamic - At the macroscopic level, it appears as if nothing is happening, but at the particulate level, reversible changes are occurring continuously. Can be at physical equilibrium or chemical equilibrium

first order half life: t½ = t when [A]t = ?? t½ = ??

[A]0/2 0.693/k

homogeneous equilibrium definition and example

all reacting species are in the same phase. gas - gas liquid-liquid liquid-aqueous

A(g) <--> B(g) The equilibrium mixture at 175°C is [A] = 2.8x10-4 M and [B] = 1.2x10-4 M. The molecular scenes below represent mixtures at various times during runs A-D of this reaction. A - Q=4 B - Q=0.43 C - Q=0.67 D - Q=0.25 Will mixture A: a) Generate more B(g) b) Generate more A(g) c) Stay the same

b) Generate more A(g)

A(g) <--> B(g) The equilibrium mixture at 175°C is [A] = 2.8x10-4 M and [B] = 1.2x10-4 M. The molecular scenes below represent mixtures at various times during runs A-D of this reaction. A - Q=4 B - Q=0.43 C - Q=0.67 D - Q=0.25 Will mixture D: a) Proceed to the left b) Proceed to the right c) Stay the same

b) Proceed to the right

The equilibrium constant (Kc) for this system is 24.0 at 200°C. Suppose that initially only cis-stilbene is present at a concentration of 0.850 mol/L. How do we calculate the concentrations of cis- and trans-stilbene at equilibrium? **ICE method

cis-stilbene <--> trans-stilbene Initial (M): Cis: 0.850 , trans: 0 Change (M): Cis: -x , trans: +x Equilibrium (M): Cis: (0.850-x), trans: x K= trans/cis = 24 = x/ (0.850-x) x= 0.816 Equilibrium: Cis: (0.850-0.816) = 0.034M trans: 0.816M

rate constant is good for ____

comparing different reactions

[A]t =

concen of A at any time t

[A]0 =

concen of A at any time t=0

A change in __ and ___ has no effect on K

concentration and pressure

k is constant, but the __ and __ change.

concentration and rate

To propose a reaction mechanism, use ___ and ___

concentration dependence and rate law

temperature changes both the equilibrium ___ and ____

concentrations and constant

rate constant

constant of the proportionality between the reaction rate and the concentration of reactant

when pressure is increased (or vol is decreased), the rxn ___ the total amount of moles of g substances involved

decrease

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if the temperature of the system is increased? If the temperature is increased, [N2] ____ , [O2] ____ , and [NO] ____

decrease, decrease, increase

in a catalyst, ___ and ____ are the same. Catalyst lowers ____. Catalyst not ____.

delta E and overall reaction Ea consumed

For which of the reactions below does Kc (calculated using concentrations) equal Kp (calculated using pressures)? (Select all that apply.) A. NO2(g) + NO3(g) <--> N2O5(g) B. CO2(g) + H2(g) <--> CO(g) + H2O(g) C. C(s) + CO2(g) <--> 2 CO(g) D. 2 MnO2(s) + 2 H2SO4(aq) <--> 2 MnSO4(s) + 2 H2O(g) + O2(g) E. NH4Cl(s) <--> NH3(g) + HCl(g) F. H2S(g) + 2 O2(g) <--> SO3(g) + H2O(g) G. N2(g) + O2(g) <--> 2 NO(g) H. CS2(g) + 3 O2(g) <--> CO2(g) + 2 SO2(g)

delta n must = 0 (moles products - moles reactants) must be same number of molecules on both sides. B. CO2(g) + H2(g) <--> CO(g) + H2O(g) G. N2(g) + O2(g) <--> 2 NO(g)

Rate changes is concentration _____ (independent/dependent)

dependent

In solubility rate of ___ = rate of ____

dissolution, precipitation

How will the rate of the following reaction change when the concentration changes by: 2NO (g) + O2 (g) --> 2NO2 (g) Rate= k[NO]^2 [O2] If O2 is doubled, the rate:

doubles rate = [1]^2[1] = 1 rate = [1]^2 [2] = 2

Example of a positive homogenous catalyst

enzymes - highly specifc, selective, and efficient - small scale reaction

Rate laws (x and y, and reactants involved) are "always" determined ____.

experimentally

rate law

expresses the relationship of the rate of a reaction to the rate constant and the concentrations of the reactants raised to some powers.

Hydrogen reacts with nitrogen monoxide to form dinitrogen monoxide (laughing gas) according to the following equation. H2(g) + 2 NO(g) → N2O(g) + H2O(g) [NO] (M) = 0.27 , 0.54, 0.54 [H2] (M) = 0.32, 0.32, 0.64 Rate (mol/L/s)= 2.100 ✕ 10^−3, 8.398 ✕ 10^−3, 1.680 ✕ 10^−2 Determine the orders with respect to each reactant. The rxn is __ order w respect to H2 and ___ order w respect to NO

first, second

Physical Equilibrium

forward and reverse processes occur at the same rate but there is no chemical change.

A =

frequency factor (collision frequency)

How will the rate of the following reaction change when the concentration changes by: 2NO (g) + O2 (g) --> 2NO2 (g) Rate= k[NO]^2 [O2] If O2 is halved, the rate:

halves rate = [1]^2 [1] = 1 rate = [1]^2 [0.5] = 0.5

what are the 5 types of catalysis?

homogenous catalysis photocatalysis biocatalysis electrocatalysis heterogenous catalysis

How will each of the following affect the rate of the reaction, CO(g) + NO2(g) → CO2(g) + NO(g), if the rate law for the reaction is rate = k [NO2] [CO]? increasing the concentration of CO from 0.04 M to 0.08 M The rate ___ by a factor of ___.

increases , 2

How will each of the following affect the rate of the reaction, CO(g) + NO2(g) → CO2(g) + NO(g), if the rate law for the reaction is rate = k [NO2] [CO]? increasing the pressure of NO2 from 0.2 atm to 0.4 atm The rate ___ by a factor of ___.

increases , 2

In the Arrhenius Equation, if Ea decreases, rate constant ____, and the rxn rate ____.

increases, increases

In the Arrhenius Equation, if temp increases, rate constant ____, and the rxn rate ____.

increases, increases

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if NO is added? If more NO is added, [N2] ____ , [O2] ____ , and [NO] ____

increases, increases, increases

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if the pressure on the system is increased by reducing the volume of the reaction vessel? If the pressure is increased by reducing the volume of the reaction vessel, [N2] ____ , [O2] ____ , and [NO] ____

increases, increases, increases

First order half-life is concentration ______ (independent/dependent)

independent

Activity

is a measure of the "effective concentration" of a species in a mixture.

rate determining step definition

is the slowest step in the sequence of steps leading to product formation.

The transition state "cannot" be ____, because its lifetime is very short.

isolated

Energy to break bonds comes from ____.

kinetic energy Kinetic energy --> Vibration energy

molecules bounce off of each other when kinetic energy (>/<) bond energy

kinetic energy < bond energy

molecules combine when kinetic energy (>/<) bond energy

kinetic energy > bond energy

Q > Kc rxn shifts ___

left

Haber-Bosch Reaction N2(g) + 3H2(g) --> 2NH3(g) Delta H°rxn = -91.8 kJ Which way does the reaction shift if: we increase the temperature?

left (less NH3. But, it gets there faster!)

How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each? H2(g) + Cl2(g) <--> 2 HCl(g) ΔH = −184.6 kJ An increase in temperature will cause the reaction equilibrium to shift to the ____. A decrease in the reaction vessel volume will cause the reaction equilibrium to ____

left, remain unchanged

How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each? 2 Cl(g) <--> Cl2(g) ΔH = −242.6 kJ An increase in temperature will cause the reaction equilibrium to shift to the ____. A decrease in the reaction vessel volume will cause the reaction equilibrium to shift to the ____

left, right

How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each? 2 H2(g) + O2(g) <--> 2 H2O(g) ΔH = −483.6 kJ An increase in temperature will cause the reaction equilibrium to shift to the ____. A decrease in the reaction vessel volume will cause the reaction equilibrium to shift to the ____

left, right

delta n =

moles of gaseous products - moles of gaseous reactants (c + d) - (a + b)

Because the reactant decreases with time, the change of the reactants are ____

negative

A <---> B means that ____ A ____ B are completely consumed during the reaction both... and neither... nor

neither... nor

A catalyst has what effect on K?

no effect

The molecularity of a reaction is the __

number of molecules reacting in an elementary step.

For a very long time since postulating this theory, the transition state even could not be ____.

observed

Example of a negative homogenous catalyst

ozone (O3) - chlorofluorocarbons (CFCs) break down and react with O3 - large scale reaction

To favor ___ formation, k fwd > k rev

product

The concentration of ____ or _____ are not included in the expression for the equilibrium constant.

pure liquids or solids

How will the rate of the following reaction change when the concentration changes by: 2NO (g) + O2 (g) --> 2NO2 (g) Rate= k[NO]^2 [O2] If NO is doubled, the rate:

quadruples rate = [1]^2 [1]= 1 rate = [2]^2 [1] = 4

third order kinetics facts

rare and slow One possibility for the mechanism of this reaction would be a three-body collision (i.e. a true termolecular reaction).

What is the rate equation for the elementary bimolecular reaction A + B → products? (Rate expressions take the general form: rate = k . [A]^a . [B]^b.)

rate = k * [A] * [B]

What is the rate equation for the elementary termolecular reaction 2 A + B → products?

rate = k * [A]^2 * [B]

Hydrogen reacts with nitrogen monoxide to form dinitrogen monoxide (laughing gas) according to the following equation. H2(g) + 2 NO(g) → N2O(g) + H2O(g) [NO] (M) = 0.27 , 0.54, 0.54 [H2] (M) = 0.32, 0.32, 0.64 Rate (mol/L/s)= 2.100 ✕ 10^−3, 8.398 ✕ 10^−3, 1.680 ✕ 10^−2 Determine the rate equation from the given data. (Rate expressions take the general form: rate = k . [A]^a . [B]^b.)

rate = k* [H2] * [NO]^2

rate = k1 * [Cl2]

rate = k2 * [CO] * [Cl]

rate = k3 * [COCl] * [Cl]

rate constant

Overall rate =

rate for slowest step

instantaneous rate

rate for specific instance in time

Overall rate law =

rate law for the slowest step

rateA --> B = kA [A] rateB --> A = kB [B] at equilibrium, the rate is

rateA --> B = rateB --> A kA [A] = kB [B] (kA / kB) = ([B]/ [A]) = K

To favor ___ formation, k fwd < k rev

reactant

heterogeneous equilibrium definition and example

reacting species are in different phases. gas - liquid liquid-solid solid-gas

In the rate law equation, x and y are the order of the ___

reaction.

Nitrogen and oxygen react at high temperatures. N2(g) + O2(g) <--> 2 NO(g) ΔH = 182.6 kJ What will happen to the concentrations of N2, O2, and NO at equilibrium if a catalyst is added? If a catalyst is added, [N2] ____ , [O2] ____ , and [NO] ____

remains same for all

Q < Kc rxn shifts ___

right

Haber-Bosch Reaction N2(g) + 3H2(g) --> 2NH3(g) Delta H°rxn = -91.8 kJ Which way does the reaction shift if: we decrease the temperature?

right (more NH3. But, it gets there slower!)

Haber-Bosch Reaction N2(g) + 3H2(g) --> 2NH3(g) Delta H°rxn = -91.8 kJ Which way does the reaction shift if: we increase the pressure?

right (more NH3.)

How will an increase in temperature affect each of the following equilibria? How will a decrease in the volume of the reaction vessel affect each? N2O3(g) <--> NO(g) + NO2(g) ΔH = 37.9 kJ An increase in temperature will cause the reaction equilibrium to shift to the ____. A decrease in the reaction vessel volume will cause the reaction equilibrium to shift to the ____

right, left

Reaction order definition

specify the relationship between the concentrations of reactants A and B and the reaction rate.

where is delta G on a curve?

starts where Ea ends and down to end of curve

Reaction mechanism

step-by-step process that occurs on a molecular level as reactants change into products.

rxn rate is ____ dependent

temp

reactions are __ and ___ dependent

temp and concen

avg kinetic energy is proportional to ___ and ____

temp and rxn rate

rate constant is __ and ___ dependent

temperature and Ea

reaction rate definition

the change in concentration per unit of time change in the concentration of a reactant or a product with time (M/s).

Activation energy (Ea)

the minimum energy that must be overcome for the reaction to occur.

Half-life (t½) definition

the time required for the concentration of a reactant to decrease to half of its initial concentration.

how to find activation energy from a graph with hump...

the top of the hump - where it starts (bottom)

time

A(g) + B(g) <--> C(g) decrease volume shifts ____

to the side with the fewest moles gas, RIGHT

where are molecules in the transition state found on a curve?

top of the hump

activated complex

transition state

Reaction intermediates are usually ___ relative to the reactants and/or products. But more ____ than transitions states.

unstable , stable

In vapor pressure, rate of ___ = rate of _____

vaporization, condensation

Pressure decrease =

volume increase

Order tells you what?

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The power coefficients __ and __ are not the same as the stoichiometric coefficients __ and __.

x and y ; a and b

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