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First Order Reactions

Rate Laws Concentration [time]. First Order Reactions Goal: convert rate law into a convenient equation to give concentrations as a function of time. For a first order reaction, the rate doubles as the concentration of a reactant doubles. Rate Laws Concentration [time].

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First Order Reactions

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  1. Rate Laws Concentration [time] • First Order Reactions • Goal: convert rate law into a convenient equation to give concentrations as a function of time. • For a first order reaction, the rate doubles as the concentration of a reactant doubles.

  2. Rate Laws Concentration [time] • First Order Reactions • A plot of ln[A]t versus t is a straight line with slope -k and intercept ln[A]0. • In the above we use the natural logarithm, ln, which is log to the base e.

  3. Rate Laws Concentration [time] • First Order Reactions

  4. Rate Laws Concentration [time] • Second Order Reactions • For a second order reaction with just one reactant • A plot of 1/[A]t versus t is a straight line with slope k and intercept 1/[A]0 • For a second order reaction, a plot of ln[A]tvs. t is not linear.

  5. Rate Laws Concentration [time] Second Order Reactions

  6. Rate Laws Concentration [time] • Half-Life • Half-life is the time taken for the concentration of a reactant to drop to half its original value. • For a FIRST ORDER process, half life, t½ is the time taken for [A]0 to reach ½[A]0. • Mathematically,

  7. Rate Laws Concentration [time] • Half-Life • For a SECOND ORDER half-life depends in the initial concentration:

  8. Rate Laws Concentration [time] • First Order Reactions • Goal: convert rate law into a convenient equation to give concentrations as a function of time. • For a first order reaction, the rate doubles as the concentration of a reactant doubles.

  9. Rate Laws Concentration [time] • First Order Reactions • A plot of ln[A]t versus t is a straight line with slope -k and intercept ln[A]0. • In the above we use the natural logarithm, ln, which is log to the base e.

  10. Rate Laws Concentration [time] • First Order Reactions

  11. Rate Laws Concentration [time] • Second Order Reactions • For a second order reaction with just one reactant • A plot of 1/[A]t versus t is a straight line with slope k and intercept 1/[A]0 • For a second order reaction, a plot of ln[A]tvs. t is not linear.

  12. Rate Laws Concentration [time] Second Order Reactions

  13. Rate Laws Concentration [time] • Half-Life • Half-life is the time taken for the concentration of a reactant to drop to half its original value. • For a FIRST ORDER process, half life, t½ is the time taken for [A]0 to reach ½[A]0. • Mathematically,

  14. Rate Laws Concentration [time] • Half-Life • For a SECOND ORDER half-life depends in the initial concentration:

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