I don't understand. The strong acid should prevent the dissociation of HX.

I understood aboue e).

The question was: Is absorbance linearly related to the wavelength?

If strong acid, equilibrium shifts pretty much completely to the left, correct? Meaning that the concentration of [HX] in solution is always the concentration of [HX] you begin with. So the concentrationof HX in solution after equilibrium, [HX]

_{e}, is the concentration you put into solution to begin with [HX]

_{0}. So if [HX]

_{0} = n, then [HX]

_{e} = n in a strongly acidified solution.

Absorbance, A is given by A = ε [HX]

_{e} L, and ε and L don't change as a function of n. Therefore A = ε n L and since ε and L are constant, A is linear with respect to n, or [HX]

_{0}.

(I guess use of n was superfluous. But easier to write out.

)

Now do the same thing for the more complicated problem where both [HX] and [X] are absorbing using the same method.

EDIT:

Re: your other question. I don't understand it. The plot is absorption vs concentration, not vs. wavelength. Absorption changes as a function of wavelength because the extinction coefficient changes as a function of wavelength, and the dependence is far from linear. There are peaks associated with molecular absorption.

EDIT2:

Fixed a small typo. Also, just keep in mind that in general, A(λ) = ε

_{HX,λ} [HX]

_{e} L + ε

_{X-,λ} [X

^{-}]

_{e} L, where in the case I've described ε

_{X-,λ} = 0 measured at λ.