Question

Determine the value of k' from the slope. These graphs were plotted in terms of absorbance, but the rate constant should be in terms of concentration. Beer-Lambert's law and the literature value for the molar absorptivity constant (87,000 M^-1cm^-1 can be used to convert the slope from units of absorbance/s to units of concentration/s. This value is the pseudo rate constant, k'.

Answer 1

k' = (2.0345 × 10⁻⁸) M/s.

Step-by-step explanation:

Beer-Lambert's law explains that Absorbance is directly proportional to the concentration of the substrate under consideration.

A ∝c

A = εlc

where ε = molar absorptivity constant = 87,000 M⁻¹cm⁻¹

l = path length of the solution that the light passes through in cm = 1 cm for most cases.

c = concentration of the substrate.

In terms of rate terms,

A' = εlc'

where A' has units of Absorbance/s

c' = rate of reaction, units of concentration/s

A' = εlc'

From the graph, the slope of the graph = 0.00177 Absorbance/s

0.00177 = 87000 × 1 × c'

c' = (0.00177/87000)

c' = (2.0345 × 10⁻⁸) M/s.

This value is the pseudo rate constant, k'.

Hope this Helps!!!