# Chemistry- Unit 1- Kinetics

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Definition of rate of reaction?
The change in concentration of any of the reactants or products with unit time.
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Using a graph, how would we find the rate of a reaction at any instant?
Draw a tangent off the graph at the particular time you wanted.
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What is the rate expression?
Tells us the contributions of the species that do affect the reaction rate, to the rate.
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Do all of the reactants appear in the reaction? Do some other things appear?
No- not all reactant concentration increases/decreases will affect the rate. But yes, we can have other things added eg: catalysts
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What is K? When does it vary?
The rate constant. varies between reactions but within the same reaction can vary dependent upon temperature.
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Example of a rate equation and meaning?
Rate = k[A]2[B] - The squared means that the rate is quadrupled if A is doubled but the rate of only doubled if B is doubled.
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How do I word this in regards to orders? Overall order?
the order in respect to A is 2 while the order in respect to B is 1.. Overall order is 3
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what is the only way of finding the rate expression?
Through experiments.
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Units of rate & concentration?
moldm-3s-1 and moldm-3
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Units for K? How do we calculate?
Changes. can be calculated by rate/the concentrations. Remember to flip the signs if there is more moldm-3 on the bottom.
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How do we use graphs to find the order of a reaction?
Plot rate agianst concentration.
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How does zero order look? 1st Order? Any orders higher?
Line going across. A positive correlation which is directly proportional. A positive correlation with an increasing gradient.
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Inital rate method?
Series of experiments are carried out at the same temperture. Only 1 species is changed at a time and the rate of reaction is recorded.
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Effect of temperature on K?
as temperature increases k increases. This is because A and B dont change with temperture but the rate changes, so therefore K must be the factor that changes.
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why?
More energy given to particles, so more particles with energy higher then the Ea so therefore more successful collisions.
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What is the rate determining step?
The step which is the slowest and therefore governs the rate of reaction (like a bottleneck).
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How can we use orders to find the rate determining step?
If we look at what species are in the rate expression, these must be present in the rate determining step as they have an effect on the rate.
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Graph curve?
Increases exponentially (so therefore an increasing positive gradient)
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## Other cards in this set

### Card 2

#### Front

Using a graph, how would we find the rate of a reaction at any instant?

#### Back

Draw a tangent off the graph at the particular time you wanted.

### Card 3

#### Front

What is the rate expression?

### Card 4

#### Front

Do all of the reactants appear in the reaction? Do some other things appear?

### Card 5

#### Front

What is K? When does it vary?