Rates Of Reaction Flashcards

1
Q

How does a zero order rate conc graph look?

A

Linear and horizontal, the rate does not change with concentration

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2
Q

How does a first order rate conc graph look?

A

The rate is proportional to the conc, so it is a positive correlation graph.

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3
Q

How does a second order rate conc graph?

A

Curve

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4
Q

How do we determine the initial rate? What is the gradient of a conc time graph?

A

Draw a tangent at t=0 on a conc time graph at the start of the reaction. Steepest gradient and fastest rate

Rate

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5
Q

What is the overall order rate of reaction?

A

Sum of the individual orders all the conc terms are raised to

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6
Q

How do we identify a first order reaction from a conc time graph? How do we know it is NOT first order?

A

The half life is constant and the same.

The half life is NOT constant.

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7
Q

How does a zero order conc time graph look?

A

Conc decreases at a constant rate

Half life decreases with time

Negative correlation

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8
Q

How does a first order conc time graph look?

A

Conc halves in equal time intervals

Half life is constant

Downwards curve

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9
Q

How does a second order conc time graph look?

A

Conc decreases rapidly, then the rate of decrease slows down

Half life increases with time

Deep curve

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10
Q

Describe what happens to the concentration as the reaction proceeds

A

As the reaction proceeds, the conc of the reactants decrease. They get used up because there are fewer collisions per second. The rate therefore slows down and the gradient gets less steep.

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11
Q

Explain the correlation between the tangent and slope

A

At any instant of time, the rate is equal to the slope of the curve

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12
Q

Explain how you can collect data for conc time graphs through continuous monitoring

A

You can continuously monitor by :

1) monitoring by gas collection ( measuring the gas volume with a gas syringe at regular time intervals )
2) mass loss

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13
Q

How do we monitor the rate with a colorimeter?

A

We measure the absorbance of a solution by looking at the wavelength of light passing through a coloured solution. This is controlled by using a filter.

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14
Q

What is the formula to calculate the rate of reaction and it’s units? What does it measure?

A

Rate = change in conc / time

Units = mol dm -3 s -1

How quickly reactants used up or products formed

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15
Q

What is the rate determining step?

A

The slowest step

Governs the overall ROR

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16
Q

What are the conditions needed for a 2 step mechanism to be valid?

A

1) the reactants in the r.d.s must be consistent with the rate equation
2) sum of all the steps must give the overall equation