Chemical Kinetics

Chemical Kinetics

Question

For the non- stoichiometric reaction 2A + B → C + D, the following kinetic data were obtained in three separate experiment, all at 298 K.

  Initial concentration (A) Initial concnetration (B) Initial rate of formation of C (mol L-1 S-1)
1 0.1 M 0.1 M 1.2 x 10-3
2 0.1 M 0.2 M 1.2 x 10-3
3 0.2 M 0.1 M 2.4 x 10-3
 The rate law for the formation of C is
  • dC over dt space equals space straight k space left square bracket straight A right square bracket left square bracket straight B right square bracket
  • dC over dt space equals space straight k open square brackets straight A squared close square brackets left square bracket straight B right square bracket
  • dC over dt space equals space straight k left square bracket straight A right square bracket left square bracket straight B right square bracket squared
  • dC over dt equals space straight k space left square bracket straight A right square bracket

Answer

D.

dC over dt equals space straight k space left square bracket straight A right square bracket straight r space equals space dC over dt space equals space straight k space left square bracket straight A right square bracket to the power of straight x left square bracket straight B right square bracket to the power of straight y
where x = order of reaction w.r.t A
 y = order of reaction w.r.t B
1.2 x 10-3 = k (0.1)x (0.1)y
1.2 x 10-3 = k (0.1)x (0.2)y
2.4 x 10-3 = k(0.2)x (0.1)y
R = k [A]1[B]0
As shown above, rate of reaction remains constant as the concentration of  reactant (B) changes from 0.1 M to 0.2 M and becomes double when concentration of A change from 0.1 to 0.2

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