Chemistry II Exam II

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Rate of reaction

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Chemistry

67 Terms

1

Rate of reaction

change in amount of a reactant or product per unit time

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2

Rate expression

Math representation of rate of reaction

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3

Rate of a reaction is equal to

rate of change of a reactant/product divided by its coefficient

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4

Are products positive or negative in rates of expression?

positive

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5

Are reactants positive or negative in rates of expression?

negative

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6

Average reaction rate

rate at which reactions proceeds over a period of time

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7

Initial reaction rate

rate at which a reaction is proceeding at a specific time

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8

Instantaneous Reaction Rate

the rate at which a reaction is proceeding at a specific time

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9

As you move down a group, the alkali metals react at a faster or slower rate with water?

faster

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10

What number tells the order of a rate law?

The exponent

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11

Are reactants the only thing in a rate law?

yes

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12

m is order with respect to

A

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13

n is oder with respect to

B

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14

What do you add to find the overall order?

m and n

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15

First order reaction equation

rate=k[a]

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16

Integration with respect to time first order equation

ln [A]0/[a]t = kt

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17

First order reaction equation in slope equation form

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

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18

Zero order has a positive or negative slope?

negative

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19

First order has a positive or negative slope?

negative

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20

Second order has a positive or negative slope?

positive

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21

Zero order plot of concentration vs time

[A] vs time

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22

First order plot of concentration vs time

ln[A]

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23

Second order plot of concentration vs time

1/[A]

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24

Integrated rate law for zero order

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

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25

Integrated rate law for second order

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

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26

Half-life definition

time it takes for half of the reacant amount to be consumed

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27

Half-life equation

[A]t = ½ [A]0

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28

Half-life equation for first order

t1/2= 0.693/k

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29

Units for 0 order reaction

m/s

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30

Units for first order reaction

s^-1

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31

Units for second order reaction

m^-1/s^-1

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32

Collision Theory

Reactants must collide in order to react with each other

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33

Rate of reaction is proportional to

rate of reactant collisions

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34

Increasing the temp often leads to an increase or decrease in rate of reaction?

increase

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35

Temperature increases the average what of reactants?

Kinetic energy

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36

Arrhenius Equation

k= Ae^ -Ea/RT

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37

The lower the Ea, the faster or slower the reaction?

Faster

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38

Catalyst only effects

activation energy

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39

Catalyst definition

Substance that can increase the reaction rate without being used up in the reaction

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40

Intermediates definition

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

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41

Why is activation energy changed by adding a catalyst?

The catalyst changes the reaction mechanism

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42

At equilibrium, the amount of reactants and products

stops changing

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43

Equilibrium equation

k= products/reactants

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44

Are solids and liquids included in equilibrium expressions?

no

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45

The reaction will reach equilibrium when most of the reactant turns into a product

large k

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46

The reaction will reach equilibrium after very little reactant has been converted to product

small k

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47

If Qc=Kc

reaction is at equilibrium

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48

If Qc is less than Kc

the reaction proceeds in the forward direction

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49

If Qc is greater than Kc

the reaction proceeds in the reverse direction

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50

Le Chatelier’s principle

When a chemical system at equilibrium is disturbed, it returns to equilibrium by counteracting the disturbance

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51

Do liquids and solids have an effect on Le Chatelier’s principle

no

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52

Four factors that affect rate of a reaction

concentration, temperature, surface area of a solid reactant, and catalysts

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53

If heat is a product

k decreases

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54

If heat is a reactant

k increases

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55

The reaction rate of a 60 degree reaction will be greater than at 30 degrees because

there is a greater proportion of reactants with the necessary kinetic energy to react

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56

What could decrease the rate of a reaction?

decreasing the surface area

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57

At equilibrium what is equal to the rate of the reverse reaction?

the rate of the forward reaction

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58

Does the magnitude of k indicate how rapidly or slowly equilibrium will be reached?

no

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59

What is the order of the reaction when a graph of ln[a] vs. time gives a straight line with a negative slope?

first

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60

What order of reaction has a linear curve when plotting concentration vs time

zero

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61

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

it decreases

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62

An increase in the temperature would result in an increase in the value of the

rate constant

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63

The molecularity of an elementary step is determined by

how many reactants are involved in the reaction

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64

To determine the rate law for a mechanism containing the equilibrium step, you must redefine

the intermediate in terms of the equilibrium step

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65

Can you have any intermediates in the rate law?

no

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66

Catalysts increase reaction rates by

providing an alternate reaction mechanism with a lower activation energy

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67

Another way to describe a species that slows down the reaction rate is

as an inhibitor

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