# 6.1 Day 6 Prelab

Questions

Consider the following hypothetical reaction between the species $$A_{(aq)}$$ and $$B_{(aq)}$$ to yield $$AB_{2(aq)}$$:

$A_{(aq)} + 2 B_{(aq)} \longrightarrow AB_{2(aq)} \nonumber$

Using the isolation method, it is found that the rate law is second order in $$A_{(aq)}$$, first-order in $$B_{(aq)}$$,and third-order overall. When 30.00 mL of 0.600 M $$A_{(aq)}$$ is combined with 20.00 mL of 0.500 M $$B_{(aq)}$$ at 25.0 °C, the initial rate of reaction is found to be 1.94 x 10-6 M/s. When 20.00 mL of 0.600 M $$A_{(aq)}$$ is combined with 30.00 mL of 0.500 M $$B_{(aq)}$$at 50.0 °C, the initial rate of reaction is found to be 6.52 x 10-6 M/s. As always, assume that all aqueous solution volumes are additive and that ionic strength was constant.

(a) Determine the rate constant of this reaction (in units of M and s) at each temperature (25.0 °C & 50.0 °C) and also determine the activation energy of this reaction (in kcal per mole of $$A_{(aq)}$$). Show all work.

(b) Clearly state any assumptions that had to be made in order to successfully carry out any of the computations in (a).

MIT OpenCourseWare
http://ocw.mit.edu

5.35 / 5.35U Introduction to Experimental Chemistry
Fall 2012