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A-level Chemistry y2 > 1: Reaction Kinetics > Flashcards

1: Reaction Kinetics Flashcards

1
Q

What does kinetics mean

A

Things related to the rate of a reaction

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2
Q

What is rate of reaction

A

The rate of change of concentration of a reaction or product with time

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3
Q

What are the units for rate for reaction

A

moldm¯³s¯¹ (or per min etc)

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4
Q

How can you find the rate of reaction from a concentration against time graph

A

Draw a tangent to the curve and calculate the gradient

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5
Q

Examples of continuous monitoring

A
  • Mass may be monitored, where the change is due to loss of a gas to the atmosphere.
  • A gas evolved in a reaction may be collected.
  • pH can be monitored using a pH meter
  • If there is a colour change in a reaction, colorimetry can be used.
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6
Q

How does a colourimeter work

A

A colorimeter uses a filter to select light in a wavelength range where there is a big difference in
the strength of absorption by the products compared to the reactants (eg strong absorption by
one and zero by the other). This light is passed through the sample and its intensity detected on
the other side

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7
Q

What is the rate equation

A

The rate equation for a reaction is an equation showing how the rate depends on the concentration of reactions

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8
Q

What is a generic rate equation

A

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

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9
Q

What is the overall order of a reaction

A

The sum of the separate orders of reaction

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10
Q

Why can’t the orders of reaction be deduced from the reaction equation

A

Because it depends on the mechanism of the reaction

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11
Q

What is k in the rate equation

A

The rate constant

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12
Q

How is the rate constant affected by the temperature and why

A

k increases as the temperature increases as the proportion of reactant molecules (or ions) with energy greater than the activation energy increases

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13
Q

Does pressure affect the rate constant

A

no

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14
Q

How does a catalyst change the rate equation

A

The whole rate equation changes as there is a new pathway with lower activation energy.

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15
Q

What is a general formula for finding the units the rate constant

A

mol^(1-x) dm^(3x-3) s¯¹

where x is the overall order of the reaction

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16
Q

What is the half life of a reaction

A

The time taken for the concentration of a reactant to fall to half of its original value

17
Q

What the rate equation for a zero order reaction

A

rate = k

18
Q

Units for the rate constant in a 0 order reaction

A

moldm¯³s¯¹

19
Q

What does the graph look like for concentration v time for zero order reaction

A

A straight line with negative gradient

20
Q

What does the rate v concentration graph look like for zero order reaction

A

Straight (horizontal) line with 0 gradient

eg. y=5

21
Q

What is the trend for successive half lives for zero order reactions

A

Successive half lives decrease (half)

22
Q

What is the rate equation for first order reaction with respect to A

A

Rate = k[A]

23
Q

What does the concentration v time graph look like for a first order reaction

A

Curved line of negative gradient

Like the positive part of 1/x

24
Q

What is the trend for successive half lives for a 1st order reaction

A

Successive half lives are constant

25
Q

Units for rate constant for 1st order reaction

A

s¯¹

26
Q

Equation for calculating half life for a 1st order reaction

A

t½= ln2 / k

27
Q

What does the rate v concentration graph look like for 1st order reaction

A

Rate is directly proportional to concentration (y=x)

28
Q

What is the rate equation for a second order reaction with respect to A

A

Rate = k[A]²

29
Q

What does the concentration v time graph look like for second order reactions

A

Curve with negative gradient

30
Q

What is the trend for successive half lives for a second order reaction

A

Successive half lives increase

31
Q

What does the rate v concentration graph look like for second order reaction

A

Curve with positive gradient (similar to the positive part of y=x²)

A-level Chemistry y2 (20 decks)

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