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CHAPTER 8
Acids, Bases, and Salts
Acids, Bases, and pH
Key Terms
Acid
Indicator
Electrolyte
Base
pH
Acids, Bases, and pH
What Are Acids?
Acids are any compound that increases the number of hydronium ions when dissolved in water
When acids dissolve in water, they ionize, which means that they form ions. The hydronium ions are responsible for the sour taste.
Acids, Bases, and pH
Indicators are compounds that can reversibly change color depending on the pH of the solution or other chemical changes.
Strong acids ionize completely
All acids ionize when dissolve in water.
A substance that conducts electricity when dissolved in water is an electrolyte
Acids, Bases, and pH
Strong acids are strong electrolytes because solutions of theses acids have as many hydronium ions as the acid can possible form
Weak acids do not ionize completely. Since they do not ionize completely they do not conduct electricity well.
Any acid can be dangerous in a concentrated form
Acids, Bases, and pH
What Are Bases?
Bases are any compound that increase the number of hydroxide ions when dissolved in water
Bases are usually bitter in taste and base solutions feel slippery
Acids, Bases, and pH
Many common bases contain hydroxide ions
Strong bases are ionic compounds that contain a metal ion and a hydroxide ion.
Like acids, bases can be very dangerous in concentrated form. Since bases attack living tissue very rapidly, base are in some ways more dangerous than acids.
Other base ionize in water to form hydroxide ions
Acids, Bases, and pH
What Is pH?
pH is a value used to express the acidity or alkalinity (base) of a solution
You can use litmus paper to tell if a solution is an acidic or basic
pH values correspond to the concentration of hydronium ions
Acids, Bases, and pH
pH is a measure of the H3O+ concentration in a solution, but pH also indicates Hydroxide ion (OH-) concentration.
Typically the pH of solutions range from 0-14
0 being Acidic
7 being Neutral
14 being Basic
Acids, Bases, and pH
Neutral - the concentration of hydroxide ions equals the concentration of hydronium ions. pH = 7
Acidic - the concentration of hydronium is greater than the concentration of hydroxide ions. pH < 7
Basic - the concentration of hydroxide is greater than the concentration of hydronium ions. pH > 7
Acids, Bases, and pH
pH can be measured in more than one way
Because ions in a solution have an electric charge, a pH meter can measure pH by determining the electric current created by the movement of the ions in the solution.
Chapter 8 Section 1 Review
1. A strong acid ionizes completely into H₃O⁺ ion and anions. A weak acid ionizes partially into H₃O⁺ ions and anions, but these recombined to form the nonionized acid. As a result, equilibrium is established with small constant concentration or ionized acid.
2. The ionization of a weak base is like the ionization of a weak acid in that only a small fraction of molecules separate into ions. The ionizations are different in that the molecules of the weak acid break apart in ionization, whereas the weak base cause water molecules to separate as electrons are accepted by the base molecule.
3. H₂O + H₂O H₃O + OH⁻
4. a. basic b. acidic c. acidic d. neutral
Chapter 8 Section 1 Review
4. a. basic b. acidic c. acidic d. neutral
5. The pH of a solution decreases as acidity increases, so the order is soft drink, vinegar, gastric juice.
6. No it is not certain that this a solution of a weak acid. It could be a weak acid or a 1 X 10⁻´ M solution of a strong acid such as HCl.
7. H₃O⁺ concentration = 0.01 M = 1 X 10⁻²M; pH = -(-2) = 2
Reactions of Acids with Bases Key Terms
Neutralization Reaction
Salt
Reactions of Acids with Bases Acid-Base Reactions
Neutralization is an ionic reaction
HCl + H₂O H₃O⁺ + Cl⁻ (ionizes)
strong acid
NaOH Na⁺ + OH⁻ (dissocaciates) strong base
Spectator Ions do not change during reactions
Reactions of Acids with Bases Strong acids and bases react to form water and
salt.
When an acid reacts with a base, hydroniumions react with hydroxide ions to form water.
Other positive and negative ions form salts
Reactions of Acids with Bases Not all neutralization reactions produce neutral
solutions
The final pH of a solution depends on the amounts of acid and base that are combined. It also depends on whether the acid and base are strong or weak.
Strong acid with weak base = an acidic solution Strong base with weak acid = a basic solution
Titrations are neutralization reactions
Reactions of Acids with Bases Titration is the process of gradually adding one solution to
another solution in the presence of an indicator to determine the concentration of one of the solutions.
Equivalence point is reached when the original amount of the acid equals the original amount of the base and occurs at pH 7
The equivalence point is not always neutral
When a strong acid is titrated with a weak base the equivalence point is not neutral.
Reactions of Acids with Bases Salts Are combinations of cations and anions
Sodium chloride has many different uses Comes from dried up seas Used as ceramic glazes, soap, water softeners
Salts are all around us Table 3 pg 267
Salts are useful substances
Chapter 8 Section 2 Review
1. 2H₃O⁺ + 2NO₃ + Mg²⁺ + 2OH⁻ → Mg²⁺ + 2NO₃ + 4H₂O or Mg(NO₃)₂ + 4H₂O
2. The Al³⁺ ion would have to come from the base, aluminum hydroxide, Al(OH)₃. The sulfate ion SO₄²⁻ would have to come from the acid sulfuric acid, H₂SO₄.
3. Li⁺ + OH⁻ + H₃O⁺ + Br⁻ → Li⁺ + Br⁻ + 2H₂O. The spectator ions are the lithium ion Li⁺, and the bromide ion Br⁻.
Chapter 8 Section 2 Review
4.1. The reaction will yield an acidic solution because sulfuric
acid is a strong acid and ammonia is a weak base.2. The reaction will yield a basic solution because formic
acid is a weak acid, and potassium hydroxide is a strong base.
3. The reaction will yield a neutral solution because nitric acid is a strong acid and calcium hydroxide is a strong base.
5. If the neutralization was done correctly, the reaction must have occurred between a strong acid and a weak base, such as ammonia. The resulting ammonium ions combine with water ions, resulting in an acidic solution. NH₄⁺ + H₂O NH₃ + H₃O⁺
Acids, Bases, and Salts in the Home
Key Terms
Soap
detergent
Disinfectant
Bleach
Antacid
Acids, Bases, and Salts in the Home Soaps allow oil and water to mix
Soap improves water’s ability to clean because it can dissolve in both oil and in water.
How does soap remove oil and dirt?
The soap allows oil and water to form an emulsion that can be washed away. This happens because the soap forms a coating around the oil that allows the oil to stay suspended in water.
Acids, Bases, and Salts in the Home Detergents have replaced soap in many uses
Detergents are water-soluble cleaner that can emulsify dirt and oil.
How do Detergents and Soaps differ?
Detergents have a sulfonate group
Soaps have a carboxylate group
Acids, Bases, and Salts in the Home Detergents are used instead of soap to was
clothes and dishes.
Many household cleaners contain ammonia.
A disinfectant is a substance that kills bacteria and viruses. Bleach is a strong disinfectant.
Acids, Bases, and Salts in the Home Does bleach remove the substance causing a
stain?
No. it changes the substance to a colorless form.
Many healthcare products are acids or bases
If you drink orange juice you are drinking Ascorbic acid or Vitamin C
Acids, Bases, and Salts in the Home Antacid is a weak base that neutralizes stomach acid.
Why are shampoos adjusted for an ideal pH?
Hair - which consists of strands of a protein called keratin - looks best when it is kept at either a slightly acidic pH or very close to neutral.
Acids keep fruits fresh longer
Acids, bases and salts in the kitchen
Chapter 8 Section 3 Review
1. Soap is a salt of a fatty acid. The anion consists of a hydrocarbon chain with a carboxyl group, COO⁻, attached. The hydrocarbon chain is similar to the molecular structure of oil so the end of the molecule dissolves in oil, while the ionic carboxyl end dissolves in water. When an oil droplet has enough soap hydrocarbon chains dissolved in it, the attraction between water and the carboxyl groups pulls the droplets into suspension where it can be washed away by rinsing.
2. Insoluble magnesium stearate is formed, which precipitates forming soap scum.
Chapter 8 Section 3 Review
3. The agitation moves suspended oily dirt particles away from the clothing enabling new detergent ions to reach the remaining dirt. The dirt becomes suspended in water and suds and can be rinsed away.
4. Usually, bleach can decolorize the stain by oxidizing the colored substance to a colorless form.
5. As a basic solution, milk of magnesia can neutralize the stomach acid, and reduce its acidity.
Chapter 8 Section 3 Review
6. Acidic materials could include vinegar (acetic acid), lemon juice (citric acid), Vitamin C (ascorbic acid), aspirin acetylsalicylic acid), buttermilk or sour cream (lactic acid), and other materials. Basic materials could include ammonia solutions, drain cleaner made with lye (sodium hydroxide), milk of magnesia (magnesium hydroxide), potash (potassium carbonate), and other materials.
7. Oil and wax are both nonpolar materials, so wax will dissolve in the oily lubricant. The nonpolar ends of the detergent molecules dissolve in the droplets of oil containing the wax, while the ionic ends dissolve in water, the agitation of the washing machine disperses the droplets throughout the water, away from the clothes and the oil rinses away.
