Acids and bases | Practice Problems, Examples & Solutions

Polarity of Bonds and Molecules

42 Practice Problems

00:46

Biochemistry

A hydrogen bond is a special case of what type of intermolecular force?

Water: The Solvent for Biochemical Reactions

06:02

Introduction to General, Organic and Biochemistry

Glycerophospholipids tend to have both a positive charge and a negative charge in their hydrophilic portions. Does this fact help or hinder lipid packing in membranes? Explain.

Lipids

03:41

Introduction to General, Organic and Biochemistry

Denaturation is usually associated with transitions from helical structures to random coils. If an imaginary process were to transform the keratin in your hair from an $\alpha$ -helix to a $\beta$ -pleated sheet structure, would you call the process denaturation? Explain.

Proteins

Intermolecular Forces

71 Practice Problems

03:42

Biochemistry

Which of the following statements is (are) true?
(a) The two strands of DNA run parallel from their 5 ' to their 3 ' ends.
(b) An adenine-thymine base pair contains three hydrogen bonds.
(c) Positively charged counterions are associated with DNA.
(d) DNA base pairs are always perpendicular to the helix axis.

Nucleic Acids: How Structure Conveys Information

01:38

Introduction to General, Organic and Biochemistry

The proton gradient accumulated in the intermembrane area of a mitochondrion drives the ATPmanufacturing enzyme, ATPase. Why do you think Mitchell called this concept the "chemiosmotic theory"?

Bioenergetics: How the Body Converts Food to Energy

03:49

Introduction to General, Organic and Biochemistry

Some of the lipid molecules that occur in membranes are bulkier than others. Are the bulkier molecules more likely to be found on the cytoplasmic side of the cell membrane or on the side facing the exterior of the cell?

Lipids

Polarity Effects on Solubilities

47 Practice Problems

02:24

Shriver & Atkins’ Inorganic Chemistry

Account for the fact that LiF and CsI have low solubility in water whereas LiI and CsF are very soluble.

The Group 1 elements

01:01

Biochemistry

RECALL What types of homogenization techniques are available for solubilizing a protein?

Protein Purification and Characterization Techniques

01:02

Biochemistry

Contemplate biochemistry if atoms did not differ in electronegativity.

Water: The Solvent for Biochemical Reactions

Arrhenius Acids and Bases

29 Practice Problems

00:18

Introduction to General, Organic and Biochemistry

Define (a) an Arrhenius acid and (b) an Arrhenius base.

Acids and Bases

01:04

Chemistry

Give Arrhenius's and Bronsted's definitions of an acid and a base. Why are Bronsted's definitions more useful in describing acid base properties?

Reactions in Aqueous Solutions

01:48

Chemistry

Give Arrhenius' and Bronsted's definitions of an acid and a base. Why are Bronsted's definitions more useful in describing acid-base properties?

Reactions in Aqueous Solutions

Bronsted-Lowry Acids and Bases

57 Practice Problems

03:04

Inorganic Chemistry

For each of the following reactions, identify the acid and the base. Also indicate which acid-base definition (Lewis. Bronsted-Lowry) applies. In some cases, more than one definition may apply.
a. $\mathrm{AlBr}_{3}+\mathrm{Br}^{-} \rightarrow \mathrm{AlBr}_{4}^{-}$
b. $\mathrm{HClO}_{4}+\mathrm{CH}_{3} \mathrm{CN} \rightarrow \mathrm{CH}_{3} \mathrm{CNH}^{+}+\mathrm{ClO}_{4}^{-}$
$\mathbf{c} . \mathrm{Ni}^{2+}+6 \mathrm{NH}_{3} \rightarrow\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}$
d. $\mathrm{NH}_{3}+\mathrm{CIF} \rightarrow \mathrm{H}_{3} \mathrm{N} \cdots$ CIF
e. $2 \mathrm{ClO}_{3}^{-}+\mathrm{SO}_{2} \rightarrow 2 \mathrm{ClO}_{2}+\mathrm{SO}_{4}^{2-}$
$\mathbf{f}, \quad \mathrm{C}_{3} \mathrm{H}_{7} \mathrm{COOH}+2 \mathrm{HF} \rightarrow\left[\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{C}(\mathrm{OH})_{2}\right]^{+}+\mathrm{HF}_{2}^{-}$

Acid–Base and Donor–Acceptor Chemistry

01:29

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Identify the Lewis acid and Lewis base in the following reactions. (Section 7.8)
(a) $\quad I_{2}+I^{-} \rightarrow I_{3}^{-}$
(b) $\mathrm{NH}_{3}+\mathrm{HBr} \rightarrow \mathrm{NH}_{4} \mathrm{Br}$
(c) $\operatorname{SiF}_{4}+2 p y \rightarrow \operatorname{SiF}_{4}(p y)_{2}$
(d) $\mathrm{CO}_{2}+\mathrm{OH}^{-} \rightarrow \mathrm{HCO}_{3}^{-}$
Which, if any, of the reactions are also Bronsted-Lowry acidbase reactions.

Acids and bases

00:10

Introduction to General, Organic and Biochemistry

Define (a) a Bronsted-Lowry acid and (b) a Bronsted-Lowry base.

Acids and Bases

Strength of Acids and Bases

182 Practice Problems

01:37

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

The acid-catalysed hydrolysis of sucrose shows first order kinetics. The half life for the reaction at room temperature was found to be 190 min. Calculate the rate constant for the reaction under these conditions. (Section $9.4)$

Reaction kinetics

03:23

Introduction to General, Organic and Biochemistry

Do you expect that the citric acid cycle will release energy or require energy? What is the reason for your answer?

Bioenergetics: How the Body Converts Food to Energy

01:09

Biochemistry

Aspirin is an acid with a $\mathrm{p} K_{\mathrm{a}}$ of $3.5 ;$ its structure includes a carboxyl group. To be absorbed into the bloodstream, it must pass through the membrane lining the stomach and the small intestine. Electrically neutral molecules can pass through a membrane more easily than can charged molecules. Would you expect more aspirin to be absorbed in the stomach, where the pH of gastric juice is about $1,$ or in the small intestine, where the pH is about $6 ?$ Explain your answer.

Water: The Solvent for Biochemical Reactions

Equilibrium Positions of Acid-Base Reactions

105 Practice Problems

06:22

Physical Chemistry

Consider the equilibrium $3 \mathrm{O}_{2}(g) \leftrightharpoons 2 \mathrm{O}_{3}(g)$
a. Using the data tables, calculate $K_{P}$ at $298 \mathrm{K}$
b. Assuming that the extent of reaction at equilibrium is much less than one, show that the degree of reaction defined as half the number of moles of $\mathrm{O}_{3}(g)$ divided by the initial number moles of $\mathrm{O}_{2}(g)$ present before dissociation is given by $\xi_{e q}=(1 / 2) \sqrt{K_{P} \times P / P^{\circ}}$
c. Calculate the degree of reaction at $298 \mathrm{K}$ and a pressure of 5.00 bar.
d. Calculate $K_{x}$ at $298 \mathrm{K}$ and a pressure of 5.00 bar.

Chemical Equilibrium

02:20

Introduction to General, Organic and Biochemistry

Write the expected products of the acid hydrolysis of the following tetrapeptide:

Proteins

02:20

Introduction to General, Organic and Biochemistry

Write balanced net ionic equations for each of the following reactions. You may need to refer to the solubility rules found in Table 4.1.
(a) An aqueous solution of nitric acid is reacted with solid barium oxide.
(b) An aqueous solution of calcium bicarbonate is reacted with hydrobromic acid solution.
(c) The gaseous hydrocarbon, acetylene $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right),$ is burned in air.
(d) An aqueous solution of aluminum sulfate is reactions with aqueous sodium hydroxide.
(e) Solid zinc strips are added to a diluted sulfuric acid solution.
(f) An aqueous solution of magnesium chloride is reaction with aqueous silver nitrate.
(g) Solid potassium is reacted with a lithium nitrate solution.

Acids and Bases

Solvent Effects on Acidity and Basicity

23 Practice Problems

02:49

Introduction to General, Organic and Biochemistry

Which are the acidic amino acids?

Proteins

01:18

Introduction to General, Organic and Biochemistry

When a solution prepared by dissolving 0.125 g of an unknown diprotic acid in $25.0 \mathrm{mL}$ of water is titrated with $0.200 \mathrm{M} \mathrm{NaOH}, 30.0 \mathrm{mL}$ of the $\mathrm{NaOH}$ solution is needed to neutralize the acid. Determine the molarity of the acid solution. What is the molar mass of the unknown diprotic acid?

Acids and Bases

01:59

Introduction to General, Organic and Biochemistry

A concentrated hydrochloric acid solution contains $36.0 \% \mathrm{HCl}$ (density $=1.18 \mathrm{g} / \mathrm{mL}$ ). How many liters are required to produce 10.0 L of a solution that has a pH of $2.05 ?$

Acids and Bases

Effects of Size and Electronegativity on Acidity

10 Practice Problems

03:14

Organic Chemistry

a. Which is more electronegative, oxygen or sulfur?
b. Which is a stronger acid, $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{H}_{2} \mathrm{S}$ ?
c. Which is a stronger acid, $\mathrm{CH}_{3} \mathrm{OH}$ or $\mathrm{CH}_{3} \mathrm{SH} ?$

Acids and Bases: Central to Understanding Organic Chemistry

09:27

Chemistry

Histidine is one of the 20 amino acids found in proteins. Shown here is a fully protonated histidine molecule where the numbers denote the $\mathrm{p} K_{\mathrm{a}}$ values of the acidic groups. (a) Show stepwise ionization of histidine in solution. (Hint: The $\mathrm{H}^{+}$ ion will first come off from the strongest acid group followed by the next strongest acid group and so on.) (b) A dipolar ion is one in which the species has an equal number of positive and negative charges. Identify the dipolar ion in (a). (c) The pH at which the dipolar ion predominates is called the isoelectric point, denoted by pI. The isoelectric point is the average of the $\mathrm{p} K_{\mathrm{a}}$ values leading to and following the formation of the dipolar ion. Calculate the pl of histidine. (d) The histidine group plays an important role in buffering blood (see Chemistry in Action on p. 732 ). Which conjugate acidbase pair shown in (a) is responsible for this action?

Acid-Base Equilibria and Solubility Equilibria

01:10

Introductory Chemistry

Refer to Figure 10.2 to determine the electronegativity of each element.
(a) $\mathrm{Mg}$
(b) $\mathrm{Si}$
(c) Br

Chemical Bonding

Inductive Effects on Acidity

16 Practice Problems

02:09

Organic Chemistry

Which of the following would you predict to be the stronger acid?

Electron Delocalization and Resonance • More About Molecular Orbital Theory

03:58

Organic Chemistry

The $\mathrm{p} K_{\mathrm{a}}$ of propene is $42,$ which is greater than the $\mathrm{p} K_{\mathrm{a}}$ of the carbon acids listed in Table 19.1, but less than the $\mathrm{p} K_{\mathrm{a}}$ of an alkane. Explain.

Carbonyl Compounds III

06:09

Chemistry

A solution of methylamine $\left(\mathrm{CH}_{3} \mathrm{NH}_{2}\right)$ has a pH of 10.64. How many grams of methylamine are there in $100.0 \mathrm{mL}$ of the solution?

Acids and Bases

Hybridization Effects on Acidity

7 Practice Problems

06:22

Organic Chemistry

Estimate the $p K_{\mathrm{a}}$ value of each of the following acids without using a calculator (i.e., between 3 and 4, between 9 and 10, etc.):
1. nitrous acid $\left(\mathrm{HNO}_{2}\right), K_{\mathrm{a}}=4.0 \times 10^{-4}$
2. nitric acid $\left(\mathrm{HNO}_{3}\right), K_{\mathrm{a}}=22$
3. bicarbonate $\left(\mathrm{HCO}_{3}^{-}\right), K_{\mathrm{a}}=6.3 \times 10^{-11}$
4. hydrogen cyanide (HCN), $K_{\mathrm{a}}=7.9 \times 10^{-10}$
5. formic acid (HCOOH), $K_{\mathrm{a}}=2.0 \times 10^{-4}$
b. Determine the $\mathrm{p} K_{\mathrm{a}}$ values, using a calculator.
c. Which is the strongest acid?

Electronic Structure and Bonding • Acids and Bases

01:59

Organic Chemistry

Explain why aldehydes and ketones react with a weak acid such as hydrogen cyanide in the presence of $^{-} \mathrm{C}=\mathrm{N},$ but do not react with strong acids such as $\mathrm{HCl}$ or $\mathrm{H}_{2} \mathrm{SO}_{4}$ in the presence of $\mathrm{Cl}^{-}$ or $\mathrm{HSO}_{4}^{-}$.

Carbonyl Compounds II

02:18

Organic Chemistry as a Language

For each pair of compounds below, predict which will be more acidic.
Graph cannot copy

ACID-BASE REACTIONS

Ranking the Four Factors

Resonance Effects on Acidity and Basicity

15 Practice Problems

00:25

Introduction to General, Organic and Biochemistry

For an acid-base reaction, one way to determine the position of equilibrium is to say that the larger of the equilibrium arrow pair points to the acid with the higher value of $\mathrm{p} K_{\mathrm{a}} .$ For example,
Explain why this rule works.

Acids and Bases

01:33

General Chemistry: Principles and Modern Applications

The equilibria $\mathrm{OH}^{-}+\mathrm{HClO} \rightleftharpoons \mathrm{H}_{2} \mathrm{O}+\mathrm{ClO}^{-}$ and $\mathrm{ClO}^{-}+\mathrm{HNO}_{2} \rightleftharpoons \mathrm{HClO}+\mathrm{NO}_{2}^{-}$ both lie to the right. Which of the following is a list of acids ranked in order of decreasing strength?(a) $\mathrm{HClO}>\mathrm{HNO}_{2}>\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{ClO}^{-}>\mathrm{NO}_{2}^{-}>\mathrm{OH}^{-}$
(c) $\mathrm{NO}_{2}^{-}>\mathrm{ClO}^{-}>\mathrm{OH}^{-}$
(d) $\mathrm{HNO}_{2}>\mathrm{HClO}>\mathrm{H}_{2} \mathrm{O}$
(e) none of these.

Acids and Bases

03:11

Organic Chemistry

Why is the $\mathrm{p} K_{\mathrm{a}}$ of the conjugate acid of morpholine significantly lower than the $\mathrm{p} K_{\mathrm{a}}$ of the conjugate acid of piperidine?

More About Amines • Heterocyclic Compounds

Lewis Acids and Bases

62 Practice Problems

01:27

Inorganic Chemistry

The proton affinities of acetone, diethylketone, and benzophenone are $812.0,836.0,$ and $882.3 \mathrm{kJ} / \mathrm{mol}$, respectively. Rationalize the ranking of these values. (Data from C. Laurence and J.-F. Gal, Lewis Basicity and Affinity Scales Data and Measurement, John Wiley and Sons, United Kingdom, $2010,$ p. $5 . .$)

Acid–Base and Donor–Acceptor Chemistry

10:02

Introduction to General, Organic and Biochemistry

Following is the structural formula of metformin, the hydrochloride salt of which is marketed as the antidiabetic medication Glucophage. Metformin was introduced into clinical practice in the United States in 1995 for the treatment of type 2 diabetes. Complete the following for metformin:
(a) Complete the Lewis structure for metformin, showing all valence electrons.
(b) Which nitrogen is the most likely site of protonation?
(c) Draw the structural formula of Glucophage.

Amines

00:59

Chemistry

Describe the following reaction in terms of the Lewis theory of acids and bases:
$$\mathrm{AlCl}_{3}(s)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{AlCl}_{4}^{-}(a q)$$

Acids and Bases

Curved-Arrow Formalism

25 Practice Problems

01:53

Organic Chemistry

Identify the electrophile and the nucleophile in each of the following reaction steps. Then draw curved arrows to illustrate the bond-making and bond-breaking processes.
- Each arrow represents the movement of two electrons from a nucleophile to an electrophile.
- The tail of the arrow is positioned where the electrons are in the reactant.
- The tail of the arrow always stars at a lone pair or a bond.
The head of the arrow points to where these electrons will end up.
- The head of the arrow always points at an atom or at a bond.

The Reactions of Alkynes • An Introduction to Multistep Synthesis

04:09

Organic Chemistry

Referring to the mechanism for the acid-catalyzed hydrolysis of methyl acetate, write the mechanism-showing all the curved arrows- -for the acid-catalyzed reaction of acetic acid and methanol to form methyl acetate. Use $\mathrm{HB}^{+}$ and : $\mathrm{B}$ to represent proton-donating and proton-removing species, respectively.

Carbonyl Compounds I

01:20

Organic Chemistry

What alkyl halides would you utilize to synthesize the following compounds, using the organoborane shown?

Reactions of Alcohols, Ethers, Epoxides, and Sulfur-Containing Compounds

Hydrocarbons

102 Practice Problems

00:54

Introduction to General, Organic and Biochemistry

Would you expect feedback inhibition to play a role in long biosynthetic pathways? Give the reason for your answer.

Biosynthetic Pathways

00:34

Introduction to General, Organic and Biochemistry

Each activation step in the synthesis of complex lipids occurs at the expense of one ATP molecule. How many ATP molecules are used in the synthesis of one molecule of lecithin?

Biosynthetic Pathways

01:44

Introduction to General, Organic and Biochemistry

Are biosynthetic pathways likely to involve oxidation, like the common catabolic pathway, or reduction? Why?

Bioenergetics: How the Body Converts Food to Energy

Functional Groups with Oxygen

60 Practice Problems

02:39

Biochemistry

How many water molecules could hydrogenbond directly to the molecules of glucose, sorbitol, and ribitol, shown here?

Water: The Solvent for Biochemical Reactions

00:19

Introduction to General, Organic and Biochemistry

What is the major difference in structure between chlorophyll and heme?

Biosynthetic Pathways

04:42

Introduction to General, Organic and Biochemistry

Acetyl-CoA is labeled with radioactive carbon as shown: $\mathrm{CH}_{3}^{*} \mathrm{CO}-\mathrm{S}-$ CoA. This compound enters the citric acid cycle. If the cycle is allowed to progress to only the $\alpha$ -ketoglutarate level, will the $\mathrm{CO}_{2}$ expelled by the cell be radioactive? Explain.

Bioenergetics: How the Body Converts Food to Energy

Functional Groups with Nitrogen

50 Practice Problems

01:12

Introduction to General, Organic and Biochemistry

What purpose do synthetic antibodies serve? Why are researchers trying to use them?

Immunochemistry

02:11

Introduction to General, Organic and Biochemistry

Is the light chain of an immunoglobulin the same as the V region?

Immunochemistry

02:17

Introduction to General, Organic and Biochemistry

(Chemical Connections 30 D) What does histamine do during its part of an inflammatory response?

Immunochemistry

pH and pKa

76 Practice Problems

01:36

Biochemistry

Define buffering capacity. How do the following buffers differ in buffering capacity? How do they differ in pH?
Buffer a: $0.01 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $0.01 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$
Buffer b: $0.10 \mathrm{M} \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $0.10 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$
Buffer $c: 1.0 M \mathrm{Na}_{2} \mathrm{HPO}_{4}$ and $1.0 \mathrm{MNaH}_{2} \mathrm{PO}_{4}$

Water: The Solvent for Biochemical Reactions

02:18

Biochemistry

MATHEMATICAL Sketch a titration curve for the amino acidd cysteine, and indicate the $\mathrm{p} K_{\mathrm{a}}$ values for all titratable groups. Also indicate the $\mathrm{pH}$ at which this amino acid has no net charge.

Amino Acids and Peptides

01:50

Introduction to General, Organic and Biochemistry

The pH of $0.10 \mathrm{M}$ HCl is $1.0 .$ When $0.10 \mathrm{mol}$ of $\mathrm{so}$ dium acetate, $\mathrm{CH}_{3} \mathrm{COONa}$, is added to this solution, its pH changes to $2.9 .$ Explain why the pH changes and why it changes to this particular value.

Acids and Bases