# Question 17.9: Calculating the Common-Ion Effect on Acid Ionization (Effect...

Calculating the Common-Ion Effect on Acid Ionization (Effect of a Strong Acid)

The degree of ionization of acetic acid, $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$, in a $0.10 \mathrm{M}$ aqueous solution at $25^{\circ} \mathrm{C}$ is 0.013. $K_{a}$ at this temperature is $1.7 \times 10^{-5}$. Calculate the degree of ionization of $\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}$ in a $0.10 \mathrm{M}$ solution at $25^{\circ} \mathrm{C}$ to which sufficient $\mathrm{HCl}$ is added to make it $0.010 \mathrm{M} \mathrm{HCl}$. How is the degree of ionization affected?

PROBLEM STRATEGY

This is an acid-ionization problem, but it differs from the simple ionization illustrated by Example 17.2. Here you have a starting concentration of $\mathrm{H}_{3} \mathrm{O}^{+}$ $(=0.010 M)$ from the addition of a strong acid $(\mathrm{HCl})$. This gives a different type of equation in Step 2, but you solve it in Step 3 by using a similar approximation method. You assume that $x$ is small compared with starting concentrations of acid and $\mathrm{H}_{3} \mathrm{O}^{+}$, so that the resulting equation is linear, rather than quadratic. The calculation of degree of ionization follows that in Example 17.2.

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Question: 17.14

## Calculating the pH at the Equivalence Point in the Titration of a Weak Acid by a Strong Base Calculate the pH of the solution at the equivalence point when 25 mL of 0.10 M nicotinic acid is titrated by 0.10 M sodium hydroxide. Ka for nicotinic acid equals 1.4 × 10^-5. PROBLEM STRATEGY At the ...

CONCENTRATION OF NICOTINATE ION Assume that the re...
Question: 17.8

## Calculating Concentrations of Species in a Salt Solution What is the pH of 0.10 M sodium nicotinate at 25°C (a problem posed in the chapter opening)? The Ka for nicotinic acid was determined in Example 17.1 to be 1.4 × 10^-5 at 25°C. ...

Sodium nicotinate gives \mathrm{Na}^{+}[/la...
Question: 17.5

## Calculating Concentrations of Species in a Weak Base Solution Using Kb Morphine, C17H19NO3, is administered medically to relieve pain. It is a naturally occurring base, or alkaloid. What is the pH of a 0.0075 M solution of morphine at 25°C? The base-ionization constant, Kb, is 1.6 × 10^-6 at 25°C. ...

Morphine, which we abbreviate as Mor, ionizes by p...
Question: 17.4

## Calculating Concentrations of Species in a Solution of a Diprotic Acid Ascorbic acid (vitamin C) is a diprotic acid, H2C6H6O6 (Figure 17.5). What is the pH of a 0.10 M solution? What is the concentration of ascorbate ion, C6H6O6^2-? The acid ionization constants are Ka1 = 7.9 × 10^-5 and ...

CALCULATION of pH Abbreviate the formula for ascor...
Question: 17.2

## Calculating Concentrations of Species in a Weak Acid Solution Using Ka (Approximation Method) What are the concentrations of nicotinic acid, hydrogen ion, and nicotinate ion in a solution of 0.10 M nicotinic acid, HC6H4NO2, at 25°C? What is the pH of the solution? What is the degree of ionization ...

STEP 1 At the start (before ionization), the conce...
Question: 17.7

## Obtaining Ka from Kb or Kb from Ka Use Tables 17.1 and 17.2 to obtain the following at 25°C: a. Kb for CN^-; b. Ka for NH4^+. ...

a. The conjugate acid of \mathrm{CN}^{-}[/l...
Question: 17.13

## Calculating the pH of a Solution of a Strong Acid and a Strong Base Calculate the pH of a solution in which 10.0 mL of 0.100 M NaOH is added to 25.0 mL of 0.100 M HCl. ...

Because the reactants are a strong acid and a stro...
Question: 17.12

## Calculating the pH of a Buffer When a Strong Acid or Strong Base Is Added Calculate the pH of 75 mL of the buffer solution described in Example 17.10 (0.10 M HC2H3O2 and 0.20 M NaC2H3O2) to which 9.5 mL of 0.10 M hydrochloric acid is added. Compare the pH change with what would occur if this amount ...

When hydronium ion (from hydrochloric acid) is add...
Question: 17.11

## Calculating the pH of a Buffer from Given Volumes of Solution Instructions for making up a buffer say to mix 60. mL (0.060 L) of 0.100 M NH3 with 40. mL (0.040 L) of 0.100 M NH4Cl. What is the pH of this buffer? PROBLEM STRATEGY The buffer contains a base and its conjugate acid in equilibrium. The ...

How many moles of $\mathrm{NH}_{3}$ a...
STEP 1 Consider the equilibrium \mathrm{HC}...