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Kinetics II

Determining orders from experiments

  • 3 things to know
  • Papers 2 and 3

Overview

The initial rate and continuous monitoring methods, deducing orders from initial rates, half-lives and rate-concentration graphs, techniques for following a rate, Core Practical 13a on the iodination of propanone, the iodine clock of Core Practical 13b, and finding k for a zero-order reaction.

What you need to know

Answer each one before you reveal it.

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Key term

What is the initial-rate method?

Key term

Using initial rates, how do you establish the order in one particular reagent?

Key term

What does half-life mean for a reaction?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the initial-rate method?

    Model answer

    Run the reaction several times, varying one reagent's starting concentration and recording the initial rate for each run.

  2. 2

    Using initial rates, how do you establish the order in one particular reagent?

    Model answer

    By seeing how the initial rate changes when the concentration of that reagent is changed, keeping others constant.

  3. 3

    If doubling a reactant's concentration doubles the rate, what is the order with respect to it?

    Model answer

    First order.

  4. 4

    If doubling a reactant's concentration quadruples the rate, what is the order with respect to it?

    Model answer

    Second order.

  5. 5

    If changing a reactant's concentration has no effect on the rate, what is the order with respect to it?

    Model answer

    Zero order.

  6. 6

    What is a continuous monitoring method?

    Model answer

    Following a single reaction over time to produce a concentration-time or volume-time graph.

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