Chapter 14 Flashcards

1
Q

Reaction rate

A

Speed at which reactions take place

Rate= change in concentration A/change in time =

Conc A2- Conca1/ t2-t1= delta[A]/ delta T

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2
Q

Factors that affect reaction rates

A

1- physical state of reactants
2- reactant concentration
3- reaction temperature
4-presence of a catalyst

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3
Q

Physical state and reactants

A

-more readily reactants the more rapid they react
-homogenous reactions ( all gas and liquids ) often faster
-heterogenous involving solis are slower , increased if the surface area increases

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4
Q

Reactant relationship with concentrations

A

Increasing concentration increases the rate of reaction

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5
Q

Temperature relating to reaction rates

A

-temp goes up so does reaction rates
-kinetics is related to temp
-higher temp molecules move faster

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6
Q

Presence of a catalyst

A

Catalyst affect rate without being in the overall balance equation

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7
Q

Instantaneous rate

A

The slope of the curve at one point in time

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8
Q

Initial rate

A

The instantaneous rate at time zero

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9
Q

Rate Law

A

Rate= k[A]^m[B]^n

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10
Q

Rate constant

A

K, specific constant at a given temperature

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11
Q

What does M and N stand for in rate law ?

A

The reaction orders which are determined by the experiment

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12
Q

Reaction Order

A

Individual order - respect tot the reactant
Order of the reaction - sum of the exponents on the reactants

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13
Q

First order

A

Rate doubles when the [A] doubles
Rate = k[A]

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14
Q

Second order

A

The rate quadruples when [A] doubles
Rate= k[A]^2

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15
Q

Zero order

A

Rate doesn’t change when [A] doubles
Rate=K

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16
Q

Determining Concentration Effect on Rate

A

We keep every concentration constant except for one reactant and see what happens to the rate

Rate1. K[A1]^x[B1]^y
———= ———————-
Rate 2. K[A2]^x[B2]^y

17
Q

Relationship of [A] with time first order reaction

A

Ln[A]= -kt + Ln[A]@

K= is the slope in a ln[a] vs time graph

18
Q

Half life first order reactions

A

T1/2 = 0.693/k

19
Q

Relationship of concentration and time in second order reactions

A

1/[A]= 1/[A]@ +kt

K= slope when 1/[A] vs time

20
Q

Half life of second order reactions

A

T1/2=1/(k[A]@)

21
Q

Zero order reactions relationship with K

A

[A]t=-kt+[A]@
Zero order directly proportional

22
Q

Factors that affect reaction rates

A

-temperature
-frequency of collisions
-orientation of molecules
-energy needed for the reaction to take place (activation energy )

23
Q

Temperature and rate

A

Temp goes up rate goes up

24
Q

Frequency of collisions

A

More collisions more reactions

25
Orientation of Molecules
Aligning molecules properly can lead to chemical reactions
26
Activation energy
The minimum energy needed for a reaction to take place
27
Transition state
The organization of the atoms at this higher energy state The lower the activation energy the faster the reaction
28
The relationship between rate constant and temperature
K=-Ea/RT + ln A K2. -Ea. (1 - 1) Ln——- = —.* ——- K1. R. (T2 T1)
29
Mechanism
Is a series of stepwise reactions hat show how reactants become products
30
Reaction Mechanism
Reaction may account all at once or through see Rea discrete steps , known as elementary reaction or elementary process.
31
Molecularity
Of elementary reaction tells how many molecules are involved in that step of the mechanism
32
Rate determining step
The slowest one is the determining step
33
When the first reaction is the slowest step ?
It’s observed that the rate law of the slow step is the rate law of the overall reaction
34
Intermediates
NOT a reactant or product NOT the transition state Usually appears in the end of the products of first step and the reactants of the second step
35
Mechanism with a fast initial step
The reactants and the products of the first step are in equilibrium with each other so Ratef=Rater
36
Catalyst
Increases the rate of the reaction by decreasing the activation energy of the reaction -homogenous -heterogeneous -enzymes
37
Homogeneous catalyst
Catalyst in same phase as reactants
38
Heterogenous catalyst
Catalyst in different phases than reactants
39
Enzymes
Protein molecules that catalyze biological reactions