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

Chapter 14 and 15 Flashcards

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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
Q

How do you get started on a rate law for a reaction mechanism when no reactions are slow?

A

Look at overall products and find something that is only produced once

26
Q

Describe the steady state approximation

A

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
Q

What can you assume if the rate of a reverse reaction is faster than the forward reaction of the next reaction?

A

The second one is slow (and therefore the first is at equilibrium)

28
Q

What is the equation for the equilibrium constant K?

aA+bB->cC+dD

A

pressure/concentration of C raised to c times D raised to d over A raised to a times B raised to b

29
Q

How does the equilibrium constant K change when reversing a reaction?

A

1/K

30
Q

How does the equilibrium constant K change when multiplying a reaction by a number?

A

K^n

31
Q

How does K tell you if products or reactants will be favored?

A

K>1 favor products, K<1 favor reactants

32
Q

What is the equation for the new K when adding equations?

A

K1*K2

33
Q

What factor will change the equilibrium constant?

A

Temperature

34
Q

What is the equation that shows how the equilibrium constant changes with temperature?

A

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

35
Q

What is the formula for converting between Kp and Kc?

A

Kp=Kc(RT)^Delta n
R is .08206 Latm over molesK
Delta n is sum of coefficients of products minus sum of coefficients of reactants

36
Q

How is Q calculated?

A

Like Kc, but the values are original, not equilibrium

37
Q

How can you tell which way a reaction will run if you have Q and K?

A

Q greater than K, reaction will move right to left

Q less than K, reaction will move left to right

38
Q

What is the quadratic formula?

A

-b +/- the square root of b^2 - 4ac all over 2a

39
Q

What simplification can you make when you are working with ICE tables and K is very small?

A

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
Q

How do you calculate percent error?

A

(theoretical-actual) over theoretical

41
Q

Describe LeChatelier’s principle

A

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
Q

Which direction will the reaction head if reactants are added?

A

Forward, toward products

43
Q

Which direction will the reaction head if products are added?

A

Backward, toward reactants

44
Q

Which direction will the reaction head if temperature is increased?

A

Whichever direction is endothermic

45
Q

Which direction will the reaction head if temperature is decreased?

A

Whichever direction is exothermic

46
Q

Which direction will the reaction head if pressure is increased?

A

The side with fewer gas molecules

47
Q

Which direction will the reaction head if pressure is decreased?

A

The side with more gas molecules

48
Q

What is the effect of adding an inert gas when a reaction is at equilibrium?

A

None, ratio of partial pressures remains the same

49
Q

What is R in atmL/moleK?

A

.08206

50
Q

What can you tell (in a set of elementary reactions that may form a possible mechanism) if the second equation is slow?

A

The first is at equilibrium

51
Q

What is R in kJ?

A

.00831447 or 8.3145x10^-3

52
Q

What is the conversion between atm and torr?

A

1 atm = 760 torr

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

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