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Chemistry · Glossary

What is Relaxation method, chemical relaxation time?

Also known as: relaxation method · chemical relaxation time

Definition 13.23 University Chemistry — Year 3 · Chapter 13 — Complex Kinetics: Chains, Enzymes and Oscillations

A relaxation method perturbs a system at equilibrium suddenly (by a jump of temperature, pressure or electric field) and follows its return to the new equilibrium. For a small perturbation the deviation decays exponentially, with the chemical relaxation time τ\tau.

Relaxation of A + B C after a temperature jump that lowered its equilibrium constant by 5 % (model: k_1 = 1.0 × 108\, L\, mol-1\, s-1, k_-1 = 1.0 × 103\, s-1, 1.0 × 10-4\, mol/ L of A and B in all): the full rate equation and the exponential with 1/ = k_1([ A]_e + [ B]_e) + k_-1 coincide.
Relaxation of A+B⇌C\mathrm{A + B \rightleftharpoons C} after a temperature jump that lowered its equilibrium constant by 5 % (model: k1=1.0×108 L mol−1 s−1k_1 = 1.0 \times 10^{8}\,\mathrm{L}\,\mathrm{mol}^{-1}\,\mathrm{s}^{-1}, k−1=1.0×103 s−1k_{-1} = 1.0 \times 10^{3}\,\mathrm{s}^{-1}, 1.0×10−4 mol/L1.0 \times 10^{-4}\,\mathrm{mol}/\mathrm{L} of A and B in all): the full rate equation and the exponential with 1/τ=k1([A]e+[B]e)+k−11/\tau = k_1([\mathrm A]_e + [\mathrm B]_e) + k_{-1} coincide.
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