Chemical Kinetics

Chemical Kinetics

Question

For a first order reaction, (A) → products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is

  • 1.73 x 10–5 M/ min

  • 3.47 x 10–4 M/min

  • 3.47 x 10–5 M/min

  • 1.73 x 10–4 M/min

Answer

B.

3.47 x 10–4 M/min

By first order kinetic rate constant,
straight k space equals space fraction numerator 2.303 over denominator straight t end fraction space log open parentheses fraction numerator straight a over denominator straight a minus straight x end fraction close parentheses
straight a space equals space 0.1 space straight M
left parenthesis straight a minus straight x right parenthesis space equals space 0.025 space straight M comma space straight t space equals space 40 space min
straight k space equals space fraction numerator 2.303 over denominator 40 end fraction space log space fraction numerator 0.1 over denominator 0.025 space straight M end fraction
equals space 0.0347 space min to the power of negative 1 end exponent
Rate space equals space open parentheses dx over dt close parentheses space equals space straight k left square bracket straight A right square bracket to the power of 1
space equals space 0.0347 space straight x space 0.01
equals space 3.47 space straight x space 10 to the power of negative 4 end exponent space straight M space min to the power of negative 1 end exponent

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