= Solution
For an elementary bimolecular forward step, $v=k_2[\mathrm R_1][\mathrm R_2]$. A liquid solution is much less compressible than a gas, so applying pressure changes its volume and reactant concentrations only modestly. With composition and temperature otherwise fixed, the observed substantial acceleration is therefore most naturally assigned to a change in the <rate constant>.
This is an approximation, not exact incompressibility: for precise pressure kinetics, correct the concentrations for compression and distinguish them from pressure-dependent activities.
Back to article page
