Fundamentals of General, Organic, and Biological Chemistry

John McMurry, David S. Ballantine, Carl A. Hoeger

Chapter 10

Acids And Bases - all with Video Answers

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Chapter Questions

Problem 1

Which of the following are Brønsted-Lowry acids?
(a) $\mathrm{HCO}_{2} \mathrm{H}$
(b) $\mathrm{H}_{2} \mathrm{~S}$
(c) $\mathrm{SnCl}_{2}$

Shahina -

Shahina -

Numerade Educator

Problem 2

Which of the following are Brønsted-Lowry bases?
(a) $\mathrm{SO}_{3}^{2-}$
(b) $\mathrm{Ag}^{+}$
(c) $\mathrm{F}^{-}$

Shahina -

Numerade Educator

Problem 3

Write formulas for:
(a) The conjugate acid of HS
(b) The conjugate acid of $\mathrm{PO}_{4}^{3-}$
(c) The conjugate base of $\mathrm{H}_{2} \mathrm{CO}_{3}$
(d) The conjugate base of $\mathrm{NH}_{4}^{+}$

Shahina -

Numerade Educator

Problem 4

For the reaction shown here, identify the Brønsted-Lowry acids, bases, and conjugate acid-base pairs.

Shahina -

Numerade Educator

Problem 5

Use Table 10.2 to identify the stronger acid in the following pairs:
(a) $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{NH}_{4}^{+}$
(b) $\mathrm{H}_{2} \mathrm{SO}_{4}$ or $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$
(c) $\mathrm{HCN}$ or $\mathrm{H}_{2} \mathrm{CO}_{3}$

Shahina -

Numerade Educator

Problem 6

Use Table 10.2 to identify the stronger base in the following pairs:
(a) $\mathrm{F}^{-}$ or $\mathrm{Br}^{-}$
(b) $\mathrm{OH}^{-}$ or $\mathrm{HCO}_{3}^{-}$

Shahina -

Numerade Educator

Problem 7

Write a balanced equation for the proton-transfer reaction between a hydrogen phosphate ion and a hydroxide ion. Identify each conjugate acid-base pair, and determine in which direction the equilibrium is favored.

Shahina -

Numerade Educator

Problem 8

Write a balanced equation for the proton transfer reaction between hydrofluoric acid (HF) and ammonia $\left(\mathrm{NH}_{3}\right)$. Identify each conjugate acid-base pair, and rewrite the equilibrium arrows to indicate if the forward or reverse reaction is favored.

Shahina -

Numerade Educator

Problem 9

From this electrostatic potential map of the amino acid alanine, identify the most acidic hydrogens in the molecule:

Shahina -

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Problem 10

Benzoic acid $\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{H}\right)$ has $K_{\mathrm{a}}=6.5 \times 10^{-5}$ and citric acid $\left(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\right)$ has
$K_{\mathrm{a}}=7.2 \times 10^{-4}$. Which is the stronger conjugate base, benzoate $\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2}^{-}\right)$ or citrate $\left(\mathrm{C}_{6} \mathrm{H}_{7} \mathrm{O}_{7}^{-}\right) ?$

Shahina -

Numerade Educator

Problem 11

Identify the following solutions as either acidic or basic. What is the value of $\left[\mathrm{OH}^{-}\right]$ in each?
(a) Household ammonia, $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=3.1 \times 10^{-12} M$
(b) Vinegar, $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=4.0 \times 10^{-3} \mathrm{M}$

Sima Sarker

Numerade Educator

Problem 12

Calculate the pH of the solutions in Problem 10.11.

Sima Sarker

Numerade Educator

Problem 13

Give the hydronium ion and hydroxide ion concentrations of solutions with the following values of $\mathrm{pH}$. Which of the solutions is most acidic? Which is most basic?
(a) $\mathrm{pH} 13.0$
(b) $\mathrm{pH} 3.0$
(c) $\mathrm{pH} 8.0$

Sima Sarker

Numerade Educator

Problem 14

Which solution would have the higher $\mathrm{pH}: 0.010 \mathrm{M} \mathrm{HNO}_{2}$ or $0.010 \mathrm{M} \mathrm{HNO}_{3}$ ? Explain.

Sima Sarker

Numerade Educator

Problem 15

Identify the following solutions as acidic or basic, estimate $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ and $\left[\mathrm{OH}^{-}\right]$ values for each, and rank them in order of increasing acidity:
(a) Saliva, $\mathrm{pH}=6.5$
(b) Pancreatic juice, $\mathrm{pH}=7.9$
(c) Orange juice, $\mathrm{pH}=3.7$
(d) Wine, $\mathrm{pH}=3.5$

Biplab Das

Numerade Educator

Problem 16

Calculate the $\mathrm{pH}$ of the following solutions and report it to the correct number of significant figures:
(a) Seawater with $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=5.3 \times 10^{-9} \mathrm{M}$
(b) A urine sample with $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=8.9 \times 10^{-6} \mathrm{M}$

Sima Sarker

Numerade Educator

Problem 17

What is the $\mathrm{pH}$ of a $0.0025 \mathrm{M}$ solution of $\mathrm{HCl} ?$

Sima Sarker

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Problem 18

How many equivalents are in the following?
(a) $5.0 \mathrm{~g} \mathrm{HNO}_{3}$
(b) $12.5 \mathrm{~g} \mathrm{Ca}(\mathrm{OH})_{2}$
(c) $4.5 \mathrm{~g} \mathrm{H}_{3} \mathrm{PO}_{4}$

Ramesh Singh

Numerade Educator

Problem 19

What are the normalities of the solutions if each sample in Problem 10.18 is dissolved in water and diluted to a volume of $300.0 \mathrm{~mL}$ ?

David Collins

Numerade Educator

Problem 20

Maalox, an over-the-counter antacid, contains aluminum hydroxide, $\mathrm{Al}(\mathrm{OH})_{3},$ and magnesium hydroxide, $\mathrm{Mg}(\mathrm{OH})_{2} .$ Write balanced equations for the reaction of both with stomach acid $(\mathrm{HCl})$

Shahina -

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Problem 21

Write a balanced equation for each of the following reactions:
(a) $\mathrm{HCO}_{3}^{-}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow ?$
(b) $\mathrm{CO}_{3}^{2-}(a q)+\mathrm{HNO}_{3}(a q) \longrightarrow ?$

Shahina -

Numerade Educator

Problem 22

What products would you expect from the reaction of ammonia and sulfuric acid in aqueous solution?

Shahina -

Numerade Educator

Problem 23

Show how ethanamine $\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}\right)$ reacts with hydrochloric acid to form an ethylammonium salt.

Shahina -

Numerade Educator

Problem 24

Predict whether the following salts produce an acidic, basic, or neutral solution:
(a) $\mathrm{K}_{2} \mathrm{SO}_{4}$
(b) $\mathrm{Na}_{2} \mathrm{HPO}_{4}$
(c) $\mathrm{MgF}_{2}$
(d) $\mathrm{NH}_{4} \mathrm{Br}$

Shahina -

Numerade Educator

Problem 25

What is the $\mathrm{pH}$ of $1.00 \mathrm{~L}$ of the $0.100 \mathrm{M}$ hydrofluoric acid- $0.120 \mathrm{M}$ fluoride ion buffer system described in Worked Example 10.16 after $0.020 \mathrm{~mol}$ of $\mathrm{HNO}_{3}$ is added?

Ramesh Singh

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Problem 26

The ammonia/ammonium buffer system is sometimes used to optimize polymerase chain reactions (PCR) used in DNA studies. The equilibrium for this buffer can be written as
$$
\mathrm{NH}_{4}^{+}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \rightleftarrows \mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{NH}_{3}(a q)
$$
Calculate the $\mathrm{pH}$ of a buffer that contains $0.050 \mathrm{M}$ ammonium chloride and $0.080 \mathrm{M}$ ammonia. The $K_{\mathrm{a}}$ of ammonium is $5.6 \times 10^{-10}$.

Sima Sarker

Numerade Educator

Problem 27

What is the ratio of hydrogen carbonate ion to carbonic acid $\left(\left[\mathrm{HCO}_{3}^{-}\right] /\left[\mathrm{H}_{2} \mathrm{CO}_{3}\right]\right)$ in blood plasma that has a pH of $7.40 ?$ (see the Chemistry in Action "Buffers in the Body: Acidosis and Alkalosis" on p. 355 ).

Ramesh Singh

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Problem 28

A buffer solution is prepared using $\mathrm{CN}^{-}$ (from $\mathrm{NaCN}$ salt) and HCN in the amounts indicated in the margin. The $K_{\mathrm{a}}$ for $\mathrm{HCN}$ is $4.9 \times 10^{-10} .$ Calculate the $\mathrm{pH}$ of the buffer solution.

Ramesh Singh

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Problem 29

A titration is carried out to determine the concentration of the acid in an old bottle of aqueous HCl whose label has become unreadable. What is the HCl concentration if $58.4 \mathrm{~mL}$ of $0.250 \mathrm{M} \mathrm{NaOH}$ is required to titrate a $20.0 \mathrm{~mL}$ sample of the acid?

Sima Sarker

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Problem 30

How many milliliters of $0.150 \mathrm{M} \mathrm{NaOH}$ are required to neutralize $50.0 \mathrm{~mL}$ of $0.200 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4} ?$ The balanced neutralization reaction is:
$$
\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{NaOH}(a q) \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)
$$.

Sima Sarker

Numerade Educator

Problem 31

A $21.5 \mathrm{~mL}$ sample of a $\mathrm{KOH}$ solution of unknown concentration requires $16.1 \mathrm{~mL}$ of $0.150 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ solution to reach the end point in a titration.
(a) How many moles of $\mathrm{H}_{2} \mathrm{SO}_{4}$ were necessary to reach the end point? How many equivalents?
(b) What is the molarity of the KOH solution?

Ramesh Singh

Numerade Educator

Problem 32

Titration of a $50.00 \mathrm{~mL}$ sample of acid rain required $9.30 \mathrm{~mL}$ of $0.0012 \mathrm{M} \mathrm{NaOH}$ to reach the end point. What was the total $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ in the rain sample? What was the $\mathrm{pH}$ ?

Ramesh Singh

Numerade Educator

Problem 33

An aqueous solution of $\mathrm{OH}^{-}$, represented as a blue sphere, is allowed to mix with a solution of an acid $\mathrm{H}_{n} \mathrm{~A},$ represented as a red sphere. Three possible outcomes are depicted by boxes $(1)-(3),$ where the green spheres represent $\mathrm{A}^{n-},$ the anion of the acid:

Ramesh Singh

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Problem 34

Electrostatic potential maps of acetic acid $\left(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\right)$ and ethanol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right)$ are shown. Identify the most acidic hydrogen in each, and tell which of the two is likely to be the stronger acid.

Shahina -

Numerade Educator

Problem 35

The following pictures represent aqueous acid solutions. Water molecules are not shown.
(a) Which picture represents the weakest acid?
(b) Which picture represents the strongest acid?
(c) Which picture represents the acid with the smallest value of $K_{\mathrm{a}} ?$

Shahina -

Numerade Educator

Problem 36

The following pictures represent aqueous solutions of a diprotic acid $\mathrm{H}_{2} \mathrm{~A} .$ Water molecules are not shown.

Shahina -

Numerade Educator

Problem 36

The following pictures represent aqueous solutions of a diprotic acid $\mathrm{H}_{2} \mathrm{~A} .$ Water molecules are not shown.
(a) Which picture represents a solution of a weak diprotic acid?
(b) Which picture represents an impossible situation?

Shahina -

Numerade Educator

Problem 37

Assume that the red spheres in the buret represent $\mathrm{H}_{3} \mathrm{O}^{+}$ ions, the blue spheres in the flask represent $\mathrm{OH}^{-}$ ions, and you are carrying out a titration of the base with the acid. If the volumes in the buret and the flask are identical and the concentration of the acid in the buret is $1.00 M$, what is the concentration of the base in the flask?

Ramesh Singh

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Problem 38

What happens when a strong acid such as HBr is dissolved in water?

Shahina -

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Problem 39

What happens when a weak acid such as $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$ is dissolved in water?

Shahina -

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Problem 40

What happens when a strong base such as $\mathrm{KOH}$ is dissolved in water?

Shahina -

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Problem 41

What happens when a weak base such as $\mathrm{NH}_{3}$ is dissolved in water?

Shahina -

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Problem 42

What is the difference between a monoprotic acid and a diprotic acid? Give an example of each.

Shahina -

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Problem 43

What is the difference between $\mathrm{H}^{+}$ and $\mathrm{H}_{3} \mathrm{O}^{+} ?$

Shahina -

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Problem 44

Which of the following are strong acids? Look at Table 10.2 if necessary.
(a) $\mathrm{HClO}_{4}$
(b) $\mathrm{H}_{2} \mathrm{CO}_{3}$
(c) $\mathrm{H}_{3} \mathrm{PO}_{4}$
(d) $\mathrm{NH}_{4}^{+}$
(e) HI
(f) $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$

Shahina -

Numerade Educator

Problem 45

Which of the following are weak bases? Look at Table 10.2 if necessary.
(a) $\mathrm{NH}_{3}$
(b) $\mathrm{Ca}(\mathrm{OH})_{2}$
(c) $\mathrm{HPO}_{4}^{2-}$
(d) $\mathrm{LiOH}$
(e) $\mathrm{CN}^{-}$
(f) $\mathrm{NH}_{2}^{-}$

Ramesh Singh

Numerade Educator

Problem 46

Identify the following substances as a Brønsted-Lowry base, a Brønsted-Lowry acid, or neither:
(a) $\mathrm{HCN}$
(b) $\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}$
(c) $\mathrm{AlCl}_{3}$
(d) $\mathrm{H}_{2} \mathrm{CO}_{3}$
(e) $\mathrm{Mg}^{2+}$
(f) $\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}$

Shahina -

Numerade Educator

Problem 47

Label the Brønsted-Lowry acids and bases in the following equations, and tell which substances are conjugate acid-base pairs.
$$
\begin{array}{l}
\text { (a) } \mathrm{CO}_{3}^{2-}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{HCO}_{3}^{-}(a q)+\mathrm{Cl}^{-}(a q) \\
\text { (b) } \mathrm{H}_{3} \mathrm{PO}_{4}(a q)+\mathrm{NH}_{3}(a q) \longrightarrow \\
& \mathrm{H}_{2} \mathrm{PO}_{4}^{-}(a q)+\mathrm{NH}_{4}^{+}(a q) \\
\text { (c) } \mathrm{NH}_{4}^{+}(a q)+\mathrm{CN}^{-}(a q) \rightleftarrows \mathrm{NH}_{3}(a q)+\mathrm{HCN}(a q) \\
\text { (d) } \mathrm{HBr}(a q)+\mathrm{OH}^{-}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{Br}^{-}(a q)
\end{array}
$$
(e) $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}(a q)+\mathrm{N}_{2} \mathrm{H}_{4}(a q) \rightleftarrows$
$$
\mathrm{HPO}_{4}^{2-}(a q)+\mathrm{N}_{2} \mathrm{H}_{5}^{+}(a q)
$$

Shahina -

Numerade Educator

Problem 48

Write the formulas of the conjugate acids of the following Brønsted-Lowry bases:
(a) $\mathrm{ClCH}_{2} \mathrm{CO}_{2}^{-}$
(b) $\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N}$
(c) $\mathrm{SeO}_{4}^{2-}$
(d) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$

Shahina -

Numerade Educator

Problem 49

Write the formulas of the conjugate bases of the following Brønsted-Lowry acids:
(a) $\mathrm{HCN}$
(b) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}_{2}^{+}$
(c) $\mathrm{H}_{3} \mathrm{PO}_{4}$
(d) $\mathrm{HSeO}_{3}^{-}$

Shahina -

Numerade Educator

Problem 50

How is $K_{\mathrm{a}}$ defined? Write the equation for $K_{\mathrm{a}}$ for the generalized acid HA.

Shahina -

Numerade Educator

Problem 51

How is $K_{\mathrm{w}}$ defined, and what is its numerical value at $25^{\circ} \mathrm{C}(298 \mathrm{~K}) ?$

Shahina -

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Problem 52

How is $\mathrm{pH}$ defined?

Shahina -

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Problem 53

A solution of $0.10 M \mathrm{HCl}$ has a $\mathrm{pH}=1.00$, whereas a solution of $0.10 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ has a $\mathrm{pH}=2.88$. Explain.

Sima Sarker

Numerade Educator

Problem 54

Calculate $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ for the $0.10 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}$ solution in Problem $10.53 .$ What percent of the weak acid is dissociated?

Ramesh Singh

Numerade Educator

Problem 55

Write the expressions for the acid dissociation constants for the three successive dissociations of phosphoric acid, $\mathrm{H}_{3} \mathrm{PO}_{4},$ in water.

Ramesh Singh

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Problem 56

Based on the $K_{\mathrm{a}}$ values in Table 10.3 , rank the following solutions in order of increasing $\mathrm{pH}: 0.10 \mathrm{M} \mathrm{HCOOH}$, $0.10 \mathrm{M} \mathrm{HF}, 0.10 \mathrm{M} \mathrm{H}_{2} \mathrm{CO}_{3}, 0.10 \mathrm{M} \mathrm{HSO}_{4}^{-}, 0.10 \mathrm{M} \mathrm{NH}_{4}^{+} .$

Shahina -

Numerade Educator

Problem 57

The electrode of a pH meter is placed in a sample of urine, and a reading of 7.9 is obtained. Is the sample acidic, basic, or neutral? What is the concentration of $\mathrm{H}_{3} \mathrm{O}^{+}$ in the urine sample?

Sima Sarker

Numerade Educator

Problem 58

A $0.10 M$ solution of the deadly poison hydrogen cyanide, HCN, has a pH of 5.2. Calculate the $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ of the solution. Is HCN a strong or a weak acid?

Ramesh Singh

Numerade Educator

Problem 59

Human sweat can have a pH ranging from 4.0 to 6.8 . Calculate the range of $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ in normal human sweat. How many orders of magnitude does this range represent?

Ramesh Singh

Numerade Educator

Problem 60

Saliva has a pH range of $5.8-7.1$. Approximately what is the $\mathrm{H}_{3} \mathrm{O}^{+}$ concentration range of saliva?

Sima Sarker

Numerade Educator

Problem 61

What is the approximate $\mathrm{pH}$ of a $0.02 \mathrm{M}$ solution of a strong monoprotic acid? Of a $0.02 M$ solution of a strong base, such as $\mathrm{KOH}$ ?

Sima Sarker

Numerade Educator

Problem 62

Calculate the $\mathrm{pOH}$ of each solution in Problems $10.57-10.61$

Ramesh Singh

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Problem 63

Without using a calculator, match the $\mathrm{H}_{3} \mathrm{O}^{+}$ concentrations of the following solutions, (a)-(d), to the corresponding $\mathrm{pH}, \mathrm{i}-\mathrm{iv}:$
(a) Fresh egg white: $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.5 \times 10^{-8} \mathrm{M}$
(b) Apple cider: $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=5.0 \times 10^{-4} \mathrm{M}$
(c) Household ammonia: $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.3 \times 10^{-12} \mathrm{M}$
(d) Vinegar (acetic acid): $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=4.0 \times 10^{-3} \mathrm{M}$
i. $\mathrm{pH}=3.30$
ii. $\mathrm{pH}=2.40$
iii. $\mathrm{pH}=11.64$
iv. $\mathrm{pH}=7.60$

Sima Sarker

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Problem 64

What are the $\mathrm{OH}^{-}$ concentration and $\mathrm{pOH}$ for each solution in Problem 10.63 ? Rank the solutions according to increasing acidity.

Ramesh Singh

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Problem 65

What are the $\mathrm{H}_{3} \mathrm{O}^{+}$ and $\mathrm{OH}^{-}$ concentrations of solutions that have the following $\mathrm{pH}$ values?
(a) $\mathrm{pH} 4$
(b) $\mathrm{pH} 11$
(c) $\mathrm{pH} 0$
(d) $\mathrm{pH} 1.38$
(e) $\mathrm{pH} 7.96$

Biplab Das

Numerade Educator

Problem 66

About $12 \%$ of the acid in a $0.10 M$ solution of a weak acid dissociates to form ions. What are the $\mathrm{H}_{3} \mathrm{O}^{+}$ and $\mathrm{OH}^{-}$ concentrations? What is the $\mathrm{pH}$ of the solution?

Sima Sarker

Numerade Educator

Problem 67

The hydrogen-containing anions of many polyprotic acids are amphoteric. Write equations for $\mathrm{HCO}_{3}^{-}$ and $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ acting as bases with the strong acid $\mathrm{HCl}$ and as acids with the strong base $\mathrm{NaOH}$.

Biplab Das

Numerade Educator

Problem 68

Write balanced equations for proton-transfer reactions between the listed pairs. Indicate the conjugate pairs, and determine the favored direction for each equilibrium.
(a) $\mathrm{HCl}$ and $\mathrm{PO}_{4}^{3-}$
(b) $\mathrm{HCN}$ and $\mathrm{SO}_{4}^{2-}$
(c) $\mathrm{HClO}_{4}$ and $\mathrm{NO}_{2}^{-}$
(d) $\mathrm{CH}_{3} \mathrm{O}^{-}$ and $\mathrm{HF}$

Ramesh Singh

Numerade Educator

Problem 69

Sodium hydrogen carbonate $\left(\mathrm{NaHCO}_{3}\right),$ also known as baking soda, is a common home remedy for acid indigestion and is also used to neutralize acid spills in the laboratory. Write a balanced chemical equation for the reaction of sodium hydrogen carbonate with
(a) Gastric juice (HCl)
(b) Sulfuric acid $\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right)$

Sima Sarker

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Problem 70

Refer to Section 10.8 to write balanced equations for the following acid-base reactions:
(a) $\mathrm{LiOH}+\mathrm{HNO}_{3} \longrightarrow$
(b) $\mathrm{BaCO}_{3}+\mathrm{HI} \longrightarrow$
(c) $\mathrm{H}_{3} \mathrm{PO}_{4}+\mathrm{KOH} \longrightarrow$
(d) $\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2}+\mathrm{HCl} \longrightarrow$
(e) $\mathrm{Ba}(\mathrm{OH})_{2}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow$
(f) $\mathrm{NH}_{3}+\mathrm{HCl} \longrightarrow$

Shahina -

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Problem 71

Rearrange the equation you wrote in Problem 10.50 to solve for $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$ in terms of $K_{\mathrm{a}^{2}}$.

Ramesh Singh

Numerade Educator

Problem 72

For each of the following salts, indicate if the solution would be acidic, basic or neutral.
(a) $\mathrm{NH}_{4} \mathrm{Cl}$
(b) $\mathrm{KBr}$
(c) $\mathrm{Na}_{2} \mathrm{CO}_{3}$
(d) $\mathrm{NaCH}_{3} \mathrm{CO}_{2}$

Shahina -

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Problem 73

Which salt solutions in problem 10.72 could be used to prepare a buffer solution? In each case, indicate which acid or base must be added to create the buffer solution.

Ramesh Singh

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Problem 74

What are the two components of a buffer system? How does a buffer work to hold pH nearly constant?

Shahina -

Numerade Educator

Problem 75

Which system would you expect to be a better buffer: $\mathrm{HNO}_{3}+\mathrm{Na}^{+} \mathrm{NO}_{3}^{-},$ or $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-} \mathrm{Na}^{+} ?$
Explain.

Ramesh Singh

Numerade Educator

Problem 76

The $\mathrm{pH}$ of a buffer solution containing $0.10 \mathrm{M}$ acetic acid and $0.10 M$ sodium acetate is 4.74 .
(a) Write the Henderson-Hasselbalch equation for this buffer.
(b) Write the equations for reaction of this buffer with a small amount of $\mathrm{HNO}_{3}$ and with a small amount of $\mathrm{NaOH}$.

Ramesh Singh

Numerade Educator

Problem 77

Which of the following buffer systems would you use if you wanted to prepare a solution having a pH of approximately $9.5 ?$
(a) $0.08 \mathrm{M} \mathrm{H}_{2} \mathrm{PO}_{4}^{-} / 0.12 \mathrm{M} \mathrm{HPO}_{4}^{2-}$
(b) $0.08 \mathrm{M} \mathrm{NH}_{4}^{+} / 0.12 \mathrm{M} \mathrm{NH}_{3}$

Ramesh Singh

Numerade Educator

Problem 78

What is the $\mathrm{pH}$ of a buffer system that contains $0.200 \mathrm{M}$ hydrocyanic acid (HCN) and $0.150 M$ sodium cyanide (NaCN)? The $p K_{3}$ of hydrocyanic acid is 9.31 .

Ramesh Singh

Numerade Educator

Problem 79

Consider $1.00 \mathrm{~L}$ of the buffer system described in Problem $10.78 .$
(a) What are the $[\mathrm{HCN}]$ and $\left[\mathrm{CN}^{-}\right]$ after $0.020 \mathrm{~mol}$ of $\mathrm{HCl}$ is added? What is the $\mathrm{pH} ?$
(b) What are the $[\mathrm{HCN}]$ and $\left[\mathrm{CN}^{-}\right]$ after $0.020 \mathrm{~mol}$ of $\mathrm{NaOH}$ is added? What is the $\mathrm{pH}$ ?

Ramesh Singh

Numerade Educator

Problem 80

What is the $\mathrm{pH}$ of a buffer system that contains $0.15 \mathrm{M}$ $\mathrm{NH}_{4}^{+}$ and $0.10 \mathrm{M} \mathrm{NH}_{3}$ ? The $\mathrm{p} K_{\mathrm{a}}$ of $\mathrm{NH}_{4}^{+}$ is 9.25.

Ramesh Singh

Numerade Educator

Problem 81

How many moles of $\mathrm{NaOH}$ must be added to $1.00 \mathrm{~L}$ of the solution described in Problem 10.80 to increase the $\mathrm{pH}$ to 9.25 ? (Hint: What is the $\left[\mathrm{NH}_{3}\right] /\left[\mathrm{NH}_{4}^{+}\right]$ when the $\left.\mathrm{pH}=\mathrm{p} K_{\mathrm{a}} ?\right)$

Ramesh Singh

Numerade Educator

Problem 82

What does it mean when we talk about acid equivalents and base equivalents?

Shahina -

Numerade Educator

Problem 83

How does normality compare to molarity for monoprotic and polyprotic acids?

Biplab Das

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Problem 84

Identify the number of equivalents per mole for each of the following acids and bases.
(a) $\mathrm{HNO}_{3}$
(b) $\mathrm{H}_{3} \mathrm{PO}_{4}$
(c) $\mathrm{KOH}$
(d) $\mathrm{Mg}(\mathrm{OH})_{2}$

Ramesh Singh

Numerade Educator

Problem 85

What mass of each of the acids and bases in Problem 10.84 is needed to prepare $500 \mathrm{~mL}$ of $0.15 \mathrm{~N}$ solution?

Ramesh Singh

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Problem 86

How many milliliters of $0.0050 \mathrm{~N} \mathrm{KOH}$ are required to neutralize $25 \mathrm{~mL}$ of $0.0050 \mathrm{~N} \mathrm{H}_{2} \mathrm{SO}_{4}$ ? To neutralize $25 \mathrm{~mL}$ of $0.0050 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4} ?$

Ramesh Singh

Numerade Educator

Problem 87

How many equivalents are in $75.0 \mathrm{~mL}$ of $0.12 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ solution? In $75.0 \mathrm{~mL}$ of a $0.12 \mathrm{M} \mathrm{H}_{3} \mathrm{PO}_{4}$ solution?

Ramesh Singh

Numerade Educator

Problem 88

How many equivalents of an acid or base are in the following?
(a) $0.25 \mathrm{~mol} \mathrm{Mg}(\mathrm{OH})_{2}$
(b) $2.5 \mathrm{~g} \mathrm{Mg}(\mathrm{OH})_{2}$
(c) $15 \mathrm{~g} \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$

Ramesh Singh

Numerade Educator

Problem 89

What mass of citric acid (triprotic, $\left.\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7} \mathrm{H}_{3}\right)$ contains $152 \mathrm{mEq}$ of citric acid?

Ramesh Singh

Numerade Educator

Problem 90

What are the molarity and the normality of a solution made by dissolving $5.0 \mathrm{~g}$ of $\mathrm{Ca}(\mathrm{OH})_{2}$ in enough water to make $500.0 \mathrm{~mL}$ of solution?

Vysakh M

Numerade Educator

Problem 91

What are the molarity and the normality of a solution made by dissolving $25 \mathrm{~g}$ of citric acid (triprotic, $\left.\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7} \mathrm{H}_{3}\right)$ in enough water to make $800 \mathrm{~mL}$ of solution?

Vysakh M

Numerade Educator

Problem 92

Titration of a $12.0 \mathrm{~mL}$ solution of $\mathrm{HCl}$ requires $22.4 \mathrm{~mL}$ of $0.12 \mathrm{M} \mathrm{NaOH}$. What is the molarity of the HCl solution?

Vysakh M

Numerade Educator

Problem 93

How many equivalents are in $15.0 \mathrm{~mL}$ of $0.12 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}$ solution? What volume of $0.085 \mathrm{M} \mathrm{HNO}_{3}$ is required to reach the end point when titrating $15.0 \mathrm{~mL}$ of this solution?

Ramesh Singh

Numerade Educator

Problem 94

Titration of a $10.0 \mathrm{~mL}$ solution of $\mathrm{NH}_{3}$ requires $15.0 \mathrm{~mL}$ of $0.0250 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ solution. What is the molarity of the $\mathrm{NH}_{3}$ solution?

Vysakh M

Numerade Educator

Problem 95

If $35.0 \mathrm{~mL}$ of a $0.100 \mathrm{~N}$ acid solution is needed to reach the end point in titration of $21.5 \mathrm{~mL}$ of a base solution, what is the normality of the base solution?

Ramesh Singh

Numerade Educator

Problem 96

For the titrations discussed in Problems 10.92 and 10.93 , what is the $\mathrm{pH}$ of the solution at the equivalence point (acidic, basic, or neutral)? Explain.

Ramesh Singh

Numerade Educator

Problem 97

For the titration discussed in Problem $10.94,$ what is the $\mathrm{pH}$ of the solution at the equivalence point (acidic, basic, or neutral)? Explain.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 98

A solution is prepared by bubbling $15.0 \mathrm{~L}$ of $\mathrm{HCl}(g)$ at $25^{\circ} \mathrm{C}(298 \mathrm{~K})$ and $101,325 \mathrm{~Pa}$ into $250.0 \mathrm{~mL}$ of water.
(a) Assuming all the HCl dissolves in the water, how many moles of $\mathrm{HCl}$ are in solution?
(b) What is the $\mathrm{pH}$ of the solution?

Ramesh Singh

Numerade Educator

Problem 99

The dissociation of water into $\mathrm{H}_{3} \mathrm{O}^{+}$ and $\mathrm{OH}^{-}$ ions depends on temperature. At $0^{\circ} \mathrm{C}(273 \mathrm{~K})$ the $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=3.38 \times 10^{-8}$
$M$, at $25^{\circ} \mathrm{C}(298 \mathrm{~K})$ the $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.00 \times 10^{-7} M,$ and at
$50^{\circ} \mathrm{C}(323 \mathrm{~K})$ the $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=2.34 \times 10^{-7} \mathrm{M}$
(a) Calculate the pH of water at $0^{\circ} \mathrm{C}(273 \mathrm{~K})$ and $50^{\circ} \mathrm{C}$ $(323 \mathrm{~K})$
(b) What is the value of $K_{\mathrm{w}}$ at $0{ }^{\circ} \mathrm{C}(273 \mathrm{~K})$ and $50^{\circ} \mathrm{C}(323 \mathrm{~K})$ ?
(c) Is the dissociation of water endothermic or exothermic?

Ramesh Singh

Numerade Educator

Problem 100

The active ingredient in aspirin is acetylsalicylic acid (Molar mass $=180.2 \mathrm{~g} / \mathrm{mol}$ ). An aspirin tablet was dissolved in water and titrated with $0.100 \mathrm{M} \mathrm{NaOH}$. If the titration required $13.87 \mathrm{~mL}$ of $\mathrm{NaOH}$ to reach the phenolphthalein endpoint, how many milligrams of acetylsalicylic acid were in the tablet?

Ramesh Singh

Numerade Educator

Problem 101

How many milliliters of $0.50 \mathrm{M} \mathrm{NaOH}$ solution are required to titrate $40.0 \mathrm{~mL}$ of a $0.10 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ solution to an end point?

Ramesh Singh

Numerade Educator

Problem 102

Which solution contains more acid, $50 \mathrm{~mL}$ of a $0.20 \mathrm{~N} \mathrm{HCl}$ solution or $50 \mathrm{~mL}$ of a $0.20 \mathrm{~N}$ acetic acid solution? Which has a higher hydronium ion concentration? Which has a lower $\mathrm{pH}$ ?

Ramesh Singh

Numerade Educator

Problem 103

One of the buffer systems used to control the pH of blood involves the equilibrium between $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ and $\mathrm{HPO}_{4}^{2-}$. The $\mathrm{p} K_{\mathrm{a}}$ for $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ is 7.21 .
(a) Write the Henderson-Hasselbalch equation for this buffer system.
(b) What $\mathrm{HPO}_{4}^{2-}$ to $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ ratio is needed to maintain the optimum blood $\mathrm{pH}$ of $7.40 ?$

Ramesh Singh

Numerade Educator

Problem 104

A 0.15 M solution of $\mathrm{HCl}$ is used to titrate $30.0 \mathrm{~mL}$ of a $\mathrm{Ca}(\mathrm{OH})_{2}$ solution of unknown concentration. If $140.0 \mathrm{~mL}$ of $\mathrm{HCl}$ is required, what is the normality of the $\mathrm{Ca}(\mathrm{OH})_{2}$ solution? What is the molarity?

Ramesh Singh

Numerade Educator

Problem 105

Which of the following combinations produces an effective buffer solution? Assuming equal concentrations of each acid and its conjugate base, calculate the $\mathrm{pH}$ of each buffer solution.
(a) $\mathrm{NaF}$ and $\mathrm{HF}$
(b) $\mathrm{HClO}_{4}$ and $\mathrm{NaClO}_{4}$
(c) $\mathrm{NH}_{4} \mathrm{Cl}$ and $\mathrm{NH}_{3}$
(d) $\mathrm{KBr}$ and $\mathrm{HBr}$

Ramesh Singh

Numerade Educator

Problem 106

One method of analyzing ammonium salts is to treat them with $\mathrm{NaOH}$ and then heat the solution to remove the $\mathrm{NH}_{3}$ gas formed.
$$
\mathrm{NH}_{4}^{+}(a q)+\mathrm{OH}^{-}(a q) \longrightarrow \mathrm{NH}_{3}(g)+\mathrm{H}_{2} \mathrm{O}(l)
$$
(a) Label the Brønsted-Lowry acid-base pairs.
(b) If $2.86 \mathrm{~L}$ of $\mathrm{NH}_{3}$ at $60^{\circ} \mathrm{C}(333 \mathrm{~K})$ and $10^{5} \mathrm{~Pa}$ is produced by the reaction of $\mathrm{NH}_{4} \mathrm{Cl}$, how many grams of $\mathrm{NH}_{4} \mathrm{Cl}$ were in the original sample?

Ramesh Singh

Numerade Educator

Problem 107

One method of reducing acid rain is "scrubbing" the combustion products before they are emitted from power plant smoke stacks. The process involves addition of an aqueous suspension of lime $(\mathrm{CaO})$ to the combustion chamber and stack, where the lime reacts with $\mathrm{SO}_{2}$ to give calcium sulfite $\left(\mathrm{CaSO}_{3}\right): \mathrm{CaO}(a q)+\mathrm{SO}_{2}(g) \longrightarrow \mathrm{CaSO}_{3}(a q)$
(a) How much lime (in grams) is needed to remove $1 \mathrm{~mol}$ of $\mathrm{SO}_{2} ?$
(b) How much lime (in kilograms) is needed to remove $1 \mathrm{~kg}$ of $\mathrm{SO}_{2} ?$

Ramesh Singh

Numerade Educator

Problem 108

Sodium oxide, $\mathrm{Na}_{2} \mathrm{O},$ reacts with water to give $\mathrm{NaOH}$.
(a) Write a balanced equation for the reaction.
(b) What is the $\mathrm{pH}$ of the solution prepared by allowing $1.55 \mathrm{~g}$ of $\mathrm{Na}_{2} \mathrm{O}$ to react with $500.0 \mathrm{~mL}$ of water? Assume that there is no volume change.
(c) How many milliliters of $0.0100 \mathrm{M} \mathrm{HCl}$ are needed to neutralize the $\mathrm{NaOH}$ solution prepared in (b)?

Ramesh Singh

Numerade Educator

Problem 109

Obtain a package of Alka-Seltzer, an antacid, from the local drug store:
(a) List the ingredients.
(b) Why does Alka-Seltzer foam and bubble when dissolved in water? Which ingredient is the antacid?
(c) Write the reaction responsible for the formation of bubbles, and the reaction responsible for the antacid activity.

Adriano Chikande

Adriano Chikande

Numerade Educator

Problem 110

Research the composition of "smelling salts"-a product that is used to rouse people who have lost consciousness.
(a) What are the primary components?
(b) What are the chemical reactions that generate the "active" component?

Crystal Wang

Numerade Educator

Problem 111

Many allergy medications contain antihistamines, compounds that contain amine groups $\left(\mathrm{R}-\mathrm{NH}_{2},\right.$ where $\mathrm{R}$ refers to an organic functional group). Would you expect these compounds to be acidic, basic or neutral? Explain.
(a) One over-the-counter product lists the active ingredient as "diphenhydramine HCl." What does this designation mean?
(b) Write the acid-base reaction to illustrate how this compound is produced. When this product is dissolved in water would you expect the solution be acidic, basic, or neutral? Explain.

Susan Hallstrom

Susan Hallstrom

Numerade Educator