Question

Iodine reacts with mesitylene to form a complex with an absorption maximum at 332 nm in CCl₄ solution:

(b)Spectrophotometric data for this reaction are shown in the table.Because$\mathbf{[}\mathbf{mesitylene}{\mathbf{]}}_{\mathbf{t}}\mathbf{ot}\mathbf{>}\mathbf{>}\mathbf{[}{\mathbf{I}}_{\mathbf{2}}\mathbf{]}\mathbf{,}$we can say that [mesitylene]$\mathbf{\approx }$[mesitylene]_tot. Prepare a graph of$\mathbf{A}\mathbf{/}\mathbf{\left(}\mathbf{\right[}\mathbf{mesitylene}\mathbf{\left]}\mathbf{\right[}{\mathbf{I}}_{\mathbf{2}}{\mathbf{]}}_{\mathbf{t}}\mathbf{ot}\mathbf{)}$versus$\mathbf{A}\mathbf{/}\mathbf{[}{\mathbf{I}}_{\mathbf{2}}{\mathbf{]}}_{\mathbf{t}}\mathbf{ot}$and find the equilibrium constant and molar absorptivity of the complex.

Short answer

The equilibrium constant is 0.464 and molar absorptivity is $1.074\cdot {10}^4{\mathrm{M}}^{-1}{\mathrm{cm}}^{-1}$.

Step-by-step solution

Define molar absorptivity.

It is measurement of how strongly a chemical species absorbs light at a given wavelength.

Draw a graph.

Calculate equilibrium constant.

From the graph, slope is -0.464. The slope is –K.

So, K = 0.464.

Using function of intercept, we calculate y- intercept.

So, the intercept is 4.984 .10³

Calculate molar absorptivity.

$$\begin{gathered} \stackrel{\text{'}}{\mathrm{O}}=\frac{\mathrm{y}-\mathrm{intercept}}{\mathrm{K}} \\ \stackrel{\text{'}}{\mathrm{o}}=\frac{4.984.{10}^3}{0.464} \\ \stackrel{\text{'}}{\mathrm{o}}=1.074.{10}^4{\mathrm{M}}^{-1}{\mathrm{cm}}^{-1} \end{gathered}$$