Chapter 16 - Further Kinetics Flashcards

1
Q

What 2 ways can rate of reaction be expressed?

A

How quickly the concentration of a product increases with time or how quickly the concentration of a reactant decreases with time

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2
Q

What is the common units of rate of reaction?

A

mol dm^-3 s^-1

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3
Q

What different methods can you use to follow rate of reaction?

A
  • measuring the volume of a gas evolved
  • measuring the change in mass of a reaction mixture
  • monitoring the colour change of a reaction
  • measuring the change in concentration using a titration
  • measuring the change in pH of a solution
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4
Q

What are the two methods of measuring the volume of gas evolved?

A
  • collection over water into a measuring cylinder

- collection using a gas syringe

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5
Q

Which more precisely measures the volume of gas evolved, gas syringes or measuring cylinder?

A

Gas syringes

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6
Q

In what situation would it not really matter whether you use a gas syringe or measuring cylinder?

A

When a large volume of gas is being measured, the difference in the degree of measurement uncertainty becomes so small that either instrument is sufficiently precise

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7
Q

What is another way of measuring rate in a reaction in which a gas is evolved?

A

Measuring the decrease is mass as the reaction proceeds.

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8
Q

When is measuring the change in mass applicable and not applicable to measure rate of reaction?

A

This technique is most precise when the gas given off has a relatively high density e.g. carbon dioxide.
However with a low-density gas such a hydrogen, the mass changes are so small that the measurement uncertainties become significant

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9
Q

What can you quantitatively measure colour with?

A

A colorimeter

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10
Q

How do you analyse rate of reaction by titration?

A
  • Use a pipette to remove small samples (aliquots) from a reaction mixture
  • The reactions in the aliquot are then quenched (the reaction is stopped)
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11
Q

How are aliquots quenched?

A

The reaction can be stopped by adding another substance or slowed down to almost zero by immersing it in an ice bath

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