Rates 2 Flashcards

1
Q

Order of reaction

A

The way in which a conc of reactant affects the rate

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2
Q

Zero order

A

Rate = [A]^0
Conc of reactant has no effect on the rate

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3
Q

First order

A

When the rate depends on its conc raised to the power of one
If conc A triples rate also triples

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4
Q

Second order

A

When the rate depends on its concentration raised to the power of 2
If conc A triples rate x9

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5
Q

Rate equation

A

Rate = k[A]^m[B]^n
Overall order = M+N

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6
Q

Conc time graphs

A

Zero order - straight line negative gradient gradient = k
First order - downward curve
k=ln2/half life
Second order - downward curve steeper at the start tailing off more slowly

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7
Q

Rate conc graphs

A

Zero order - horizontal line
Rate=k
First order - k[A] straight line through origin proportional
Second order - rate=k[A]^2 curve
Plot again conc^2 straight line through origin

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8
Q

Initial rate

A

instantaneous rate at start of reaction
Can be found measuring gradient of tangent at t=0 on conc time graph
Initial rate of clock = 1/t

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9
Q

Rate determining step

A

Slowest step in a reaction
Multiple step reactions
Eg rate = k [x]^2
2X -> Xy+ Xc
Xc +Y -> 2XY

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10
Q

Factors affecting the rate constant

A

Increasing the temp increases the activation energy

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11
Q

Arrhenius equation

A

K= A x e^-Ea/RT

A= (pre exponential factor)
R= Gas constant
T = temp

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12
Q

Arrhenius plot

A

ln k = -Ea/R x 1/t + lnA

-Ea/R = gradient
1/t= x value
lnA = y intercept

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13
Q

Equilibrium constant Kc

A

Only gases
If homogeneous species Kc uses all in equation
If heterozygous species Kc only uses gases in the equation

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14
Q

Calculating equilibrium quant to calculate Kc

A

Reacting amounts
Initial
Change
Equilibrium
USE RICE TABLES
Divide by total volume and sun into to Kc equation

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15
Q

Kp

A

Is the equilibrium constant used for gases

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16
Q

Mole fraction

A

No of moles of A/No of moles in gas mixture

17
Q

Partial pressure

A

Contribution has makes towards the total pressure
Mole fraction x total pressure

18
Q

Kp equation

A

p(products)/p(reactants)

19
Q

K=1

A

Equilibrium half way between products and reactants

20
Q

K=100

A

Equilibrium well in favour of products

21
Q

K=1x10^-3

A

Equilibrium well in favour of reactants

22
Q

Exothermic effects on K

A

If forwards reaction is Exothermic
Raising the temp decreases K
Due to equilibrium shifting more towards reactants

23
Q

Explaining equil shift

A

System is no longer in equilibrium and Kp ratio is greater than Kp
Equil partial pressures must change
Product decr reactants incr
Equil shifts to the left

24
Q

How does conc affect K

A

If conc of reactants increased the ratio is now less than Kc so no longer in equil
Conc of product incr conc of reactant decr
New equilibrium shifts right to restore Kc value

25
Q

How does pressure affect K

A

If reactant pressure incr and product
Product must decrease and reactant increase to restore Kp value