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Chapter 14: Problem 168

For solutions of the same concentration, as acid strength increases, indicate what happens to each of the following (increases, decreases, or doesn't change). $$ \begin{array}{ll}{\text { a. }\left[\mathrm{H}^{+}\right]} & {\text { d. pOH }} \\ {\text { b. pH }} & {\text { e. } K_{\mathrm{a}}} \\ {\text { c. }\left[\mathrm{OH}^{-}\right]}\end{array} $$

Short Answer

Expert verified
As acid strength increases in solutions of the same concentration, the following changes are observed: a. \([H^+]\) ion concentration increases. b. pH decreases. c. \([OH^-]\) ion concentration decreases. d. pOH increases. e. \(K_a\) (Acid dissociation constant) increases.

Step by step solution

01

a. H+ ion concentration

When the acid strength increases, the concentration of H+ ions will also increase as the acid becomes more effective at releasing its protons. So, H+ ion concentration increases.
02

b. pH

The pH scale is defined as pH = -log10[H+]. Since the H+ ion concentration increases as the acid strength increases, the pH of the solution will become lower (more negative logarithm). Therefore, the pH decreases.
03

c. OH- ion concentration

As the concentration of H+ ions increases, the concentration of OH- ions decreases to maintain the balance and keep the product of [H+] and [OH-] equal to the ion product of water (Kw = 1.0 × 10^(-14) at 25°C). So, OH- ion concentration decreases.
04

d. pOH

pOH is defined as pOH = -log10[OH-]. Since the OH- ion concentration decreases as the acid strength increases, the pOH of the solution will become higher (more negative logarithm). Therefore, pOH increases.
05

e. Ka (Acid dissociation constant)

Ka is defined as the ratio of the concentration of the dissociated form of an acid to the concentration of the undissociated form at equilibrium: Ka = ([H+][A-]) / [HA]. As the acid strength increases, more molecules dissociate into H+ ions and A- ions, and the Ka value representing the degree of ionization also increases. So, Ka increases.

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Most popular questions from this chapter

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