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Z - Chemistry 1320 (S&T) > Chapter 14 and 15 > Flashcards

Chapter 14 and 15 Flashcards

1
Q

What is the formula for average rate?

A

Change in concentration over change in time

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2
Q

How do you find instantaneous rate?

A

Slope of the tangent line

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3
Q

How do you find the order of each of the reactants from experiments?

A

Concentration doubles as rate increases by 2^1 = first order

Concentration doubles as rate increases by 2^2 = second order

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4
Q

What is the general rate law?

A

Rate=k[X]^y

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5
Q

What is the first order integrated rate law?

A

Ln [A]t = -kt + Ln[A]0

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6
Q

What does the straight line graph look like for a first order reaction?

A

Ln[A] vs t with a slope of -k and a y-intercept of ln[A]0

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7
Q

What is the half-life formula for a first order reaction?

A

Ln2/k

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8
Q

What is the second order integrated rate law?

A

1/[A]t = kt + 1/[A]0

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9
Q

What does the straight line graph look like for a second order reaction?

A

1/[A]t vs t with a slope of k and a y-intercept of 1[A]0

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10
Q

What is the half-life formula for a second order reaction?

A

1/([A]0 * k)

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11
Q

What are the two tenets of collusion theory?

A

the reactants must collide with a energy greater than a minimum energy (E>Emin) and with the right orientation

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12
Q

What is the Arrhenius equation that only has one temperature?

A

Ln k = Ln A - Emin/RT or K = A times e^(-Emin/RT)

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13
Q

What is the Arrhenius equation that relates two temperatures?

A

Ln (K2/K1) = -Emin/R (1/T2 - 1/T1)

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14
Q

What is the value of R in J/molK?

A

8.3145J/molK

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15
Q

On an Potential Energy vs Reaction Coordinate Graph, how do you find Ea?

A

Distance from reactants/products to top of hill

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16
Q

On an Potential Energy vs Reaction Coordinate Graph, how do you find the transition state?

A

Top of hill

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17
Q

On an Potential Energy vs Reaction Coordinate Graph, how do you find Delta E/H?

A

Difference between products and reactants

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18
Q

On an Potential Energy vs Reaction Coordinate Graph, how can you tell endothermic/exothermic?

A

endothermic- +Delta H/E, products are higher, Ea of forward reaction is higher (all opposite for exothermic)

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19
Q

On an Potential Energy vs Reaction Coordinate Graph, what is the role of a catalyst?

A

to increase reaction rate by reducing Ea

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20
Q

What is the Arrhenius equation relating the rates of a reaction with and without a catalyst?
Include the equation for when temperature is different.

A

Ln (rate cat/rate uncat) = Delta Ea / RT (same temperature/A)

His-Rate cat/Rate uncat = e^((Ea noncat- Ea cat )/ RT)

DiffTemp-
ratecat/rateuncat = e^(Eanoncat/RTnoncat minus Eacat/RTcat)

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21
Q

How do the forward and backwards Ea relate?

A

Ea reverse = Ea forward + Delta H or E (Delta H is equal to Delta E)

22
Q

What is the equation for bond energies and delta H?

A

Delta H is energy in reactant minus products

23
Q

What are the three things that prove a reaction mechanism is possible?

A

Adds up to overall, same rate law, presence of intermediates

24
Q

How do you get the rate law from a reaction mechanism when one step is slow?

A

Rate law of the slow elementary reaction is the rate law of overall (may need to substitute to get rid of intermediates)

25
How do you get started on a rate law for a reaction mechanism when no reactions are slow?
Look at overall products and find something that is only produced once
26
Describe the steady state approximation
Make an assumption that the intermediate’s concentration never accumulates, and remains steady. It remains steady only if the rate of formation is equal to the rate of consumption.
27
What can you assume if the rate of a reverse reaction is faster than the forward reaction of the next reaction?
The second one is slow (and therefore the first is at equilibrium)
28
What is the equation for the equilibrium constant K? | aA+bB->cC+dD
pressure/concentration of C raised to c times D raised to d over A raised to a times B raised to b
29
How does the equilibrium constant K change when reversing a reaction?
1/K
30
How does the equilibrium constant K change when multiplying a reaction by a number?
K^n
31
How does K tell you if products or reactants will be favored?
K>1 favor products, K<1 favor reactants
32
What is the equation for the new K when adding equations?
K1*K2
33
What factor will change the equilibrium constant?
Temperature
34
What is the equation that shows how the equilibrium constant changes with temperature?
Ln (K2/K1) = -Delta H/R (1/T2 - 1/T1)
35
What is the formula for converting between Kp and Kc?
Kp=Kc(RT)^Delta n R is .08206 L*atm over moles*K Delta n is sum of coefficients of products minus sum of coefficients of reactants
36
How is Q calculated?
Like Kc, but the values are original, not equilibrium
37
How can you tell which way a reaction will run if you have Q and K?
Q greater than K, reaction will move right to left Q less than K, reaction will move left to right
38
What is the quadratic formula?
-b +/- the square root of b^2 - 4ac all over 2a
39
What simplification can you make when you are working with ICE tables and K is very small?
You can assume the x’s on the bottom are very small and leave them off (Check simplification by doing a percent error calculation, error should be below 5%)
40
How do you calculate percent error?
(theoretical-actual) over theoretical
41
Describe LeChatelier's principle
If a change in conditions (a “stress”) is imposed on a system at equilibrium, the equilibrium position will shift in the direction that tends to reduce the effect of the change in conditions
42
Which direction will the reaction head if reactants are added?
Forward, toward products
43
Which direction will the reaction head if products are added?
Backward, toward reactants
44
Which direction will the reaction head if temperature is increased?
Whichever direction is endothermic
45
Which direction will the reaction head if temperature is decreased?
Whichever direction is exothermic
46
Which direction will the reaction head if pressure is increased?
The side with fewer gas molecules
47
Which direction will the reaction head if pressure is decreased?
The side with more gas molecules
48
What is the effect of adding an inert gas when a reaction is at equilibrium?
None, ratio of partial pressures remains the same
49
What is R in atm*L/mole*K?
.08206
50
What can you tell (in a set of elementary reactions that may form a possible mechanism) if the second equation is slow?
The first is at equilibrium
51
What is R in kJ?
.00831447 or 8.3145x10^-3
52
What is the conversion between atm and torr?
1 atm = 760 torr

Z - Chemistry 1320 (S&T) (3 decks)

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