Chapter 22 Acids, Bases, and Salts Section 1: Acids and Bases Section 2: Strength of Acids and Bases Section 3: Salts

Section 1: Acids and Bases Standard 3: Demonstrate an understanding of various properties and classifications of matter. Objectives: Compare and contrast acids and bases and identify the characteristics they have. Examine some formulas and uses of common acids and bases. Determine how the process of ionization and dissociation apply to acids and bases.

Acids Acid - a substance that produces hydrogen ions (H+) in a water solution. All acids contain at least one H atom that can be removed when dissolved in water. Examples:

Hydronium ion- is H3O+. When an acid dissolves in water, H+ ions interact with water molecules to form H3O+

Properties of Acids Properties of acids: Sour taste Can burn skin Corrosive React with active metals (Zn and Mg) and form hydrogen gas & some other compound Conduct electricity Turn litmus paper red pH less than 7

Common acids and their uses Acetic Acid (CH3COOH) is in vinegar; used in preserving foods ASA [Acetylsalicylic acid, C9H8O4] is main component of aspirin; used in pain relievers

Common acids Ascorbic acid (C6H8O6) is vitamin C; found in citrus fruits Carbonic acid is in soda pop; it makes pop carbonated. It is also dissolves rocks and is involved in cave formation

Common acids Hydrochloric acid (HCl) is in your stomach to break down food. It is used in industry to clean steel in a process called pickling Lactic acid (C3H6O3) is produced in muscles when you exercise too much too fast. It is also what makes milk go sour. In yogurt & buttermilk. Nitric acid (HNO3) is colorless but turns yellow when exposed to light. Used in making fertilizers. Very nasty stuff.

Common acids Phosphoric acid (H3PO4) is in soda pop, detergents, and fertilizers. Detergents that contain phosphates (PO43-) create pollution. Sulfuric acid (H2SO4) is in car batteries. Will pull water from the air if left open. Used in making paper. Very nasty stuff also.  

Common Acids Common acids: citric acids (citric fruits), lactic acid (yogurt and milk), acetic acid (vinegar), HCl (stomach)

Detecting Acids and Bases Indicator - organic compound that changes a certain color with acids and another color with bases. ex) litmus paper is red in acid & blue in base pH paper phenolphthalein solution

Indicators An indicator is an organic compound that changes color in acid and in base. Example: Litmus is red in acid and blue in base.

Bases Base - substance that forms hydroxide ions, OH-, in a water solution. A base is also defined as any substance that accepts H+ from acids  

Properties of Bases Properties of Bases: Crystalline solids in undissolved state Bitter taste Slippery feel Can burn skin Corrosive Conduct electricity pH greater than 7 Turn litmus paper blue

Common bases and their uses Aluminum hydroxide [Al(OH)3] is a sticky gel-like material used as a water purifyer; used as an antacid, in water purification, and making fabrics. Calcium hydroxide [Ca(OH)2] is in “lime” for gardens and lawns. Used in plaster and making leather products. Magnesium hydroxide [Mg(OH)2] is in antacids and laxatives. In “milk of magnesia”.

Common bases Sodium hydroxide [NaOH] is called “lye” and “caustic soda”. Used in making soap, oven cleaner, drain opener, fabrics, paper. Very nasty stuff Ammonia [NH3] is very bad smelling; can damage lungs. Used in cleaners, fertilizers, and to make fabrics.  

Common Bases Common bases: sodium hydroxide and calcium hydroxide

Ionization of Acids The acid ionizes (or separates) into ions and the hydrogen atom combines with a water molecule to form hydronium ions (H3O+). The negative areas of water attract to the positive H in the acid to form H3O+.

Dissociation of Bases When bases dissolve in water, the negative areas of nearby water molecules attract to the positive ion in the base. The positive areas of nearby water molecules attract to the –OH of the base.

Ammonia Ammonia (NH3) is a base that does not contain –OH. Ammonia molecule attracts a hydrogen ion from a water molecule, forming an ammonium ion (NH4+).

Review Questions What does an acid produce in solution?

Review Questions What does an acid produce in solution? An acid produces hydrogen ions in solution, which interact with water molecules to form hydronium ions.

Review Questions Which changes color in acids and bases? What category of chemicals is it? A. ammonia B. antacid C. detergent D. Litmus paper

Review Questions Which changes color in acids and bases? What category of chemicals is it? D. Litmus paper; indicator

Review Questions Any substance that forms __________ in a water solution is a base. A. H3O+ B. OH - C. H + D. H2O

Review Questions Any substance that forms __________ in a water solution is a base. B. OH -

Review Questions What is the pH range for acids?

Review Questions What is the pH range for acids? 0 - 6

Review Questions What is the pH range for bases?

Review Questions What is the pH range for bases? 8 - 14

6. Identify three important bases and describe their uses.

7. If an acid donates H+ and a base produces OH-, what compound if likely to be produced when acids react with bases

Section 2: Strengths of Acids and Bases Standard 3: Demonstrate an understanding of various properties and classifications of matter. Indicators: 3.8 Objectives: Determine what is responsible for the strength of an acid or a base. Compare and contrast strength and concentration. Examine the relationship between pH and acid or base strength. Examine electrical conductivity.

Strength of Acids and Bases The strength of an acid or base depends on how many acid or base particles dissociate into ions in water.

Strength of Acids and Bases Strong acid- when it dissolves in water, nearly all the acid molecules dissociate into ions. Examples: HCl, HNO3, and H2SO4. A strong acid solution conducts more current because more ions are formed. Light bulb is bright.

Weak acid- when it dissolves in water, only a small fraction of the molecules dissolve in water. Examples: acetic acid and carbonic acid A weak acid solution does not conduct as much current because less ions are formed.Light bulb would be dim.

Strong and Weak Acids Strong acid - nearly all the acid molecules dissociate into ions. Weak acid - only a small fraction of the molecules dissolve in water.

Strong and Weak Bases Strong base - dissociates completely in solution. Weak base - does not dissociate completely.

Strength & Concentration Strong and weak refer to the degree to which an acid or base ionizes Dilute and concentrated are used to indicate the concentration of a solution, which is the amount of acid or base dissolved in the solution.

You can have a dilute solution of a strong acid You can have a concentrated solution of a weak acid

pH pH - measure of the concentration of H+ ions in a solution. The greater the H+ concentration  more acidic Lower the H+ concentration  more basic

pH The pH scale ranges from 0 to 14. pH less than 7 are acidic (more H+). pH greater than 7 are basic (More OH-). pH of 7 is neutral (H+ ions and OH- ions are equal). Each value is 10x more or less acidic than the next pH of blood must remain between 7.0 and 7.8

Detecting Acids and Bases pH can be determined by using: pH paper which changes color pH meter Indicators can tell if it’s an acid or base, but cannot tell you a pH

Buffers Buffers - solutions containing ions that react with additional acids or bases to minimize their effects on pH. Your blood has buffers that make it resistant to changes in pH.

Review Questions What is the difference between a strong acid and a weak acid?

Review Questions What is the difference between a strong acid and a weak acid? In strong acids, nearly all the acid molecules dissociate into ions. In weak acids, a small fraction of the molecules dissolve in water.

Review Questions What is the difference between the terms “strength” and “concentration”?

Review Questions What is the difference between the terms “strength” and “concentration”? Strength refers to the ease with which an acid or base dissociates in solution. Concentration is the amount of an acid or base dissolved in the solution.

Review Questions The pH of a solution is a measure of the concentration of _________ in the solution.

Review Questions The pH of a solution is a measure of the concentration of H+ in the solution.

Review Questions (T/F) The lower the H+ concentration, the more basic the solution.

Review Questions (T/F) The lower the H+ concentration, the more basic the solution. True

Review Questions What is the range of the pH scale?

Review Questions What is the range of the pH scale? 0 - 14

Describe what determines the strength of an acid. A base?

~Depends on how many acid or base particles dissociate into ions in water

7. Explain how to make a dilute solution of a strong acid.

8. Explain how electricity can be conducted by solutions

More ions a solution contains, the more current it can conduct.

9. Describe pH values of 9.1, 1.2, and 5.7 as basic, acidic, or very acidic.

1.2: very acidic 5.6: acidic 9.1: basic

How much more acidic is a solution of pH 2 than a solution of pH 4?

100

Section 3: Salts Standard 3: Demonstrate an understanding of various properties and classifications of matter. Indicators: 3.8 Objectives: Identify a neutralization reaction.

Neutralization Neutralization - chemical reaction between an acid and a base that takes place in a water solution.

Salt Formation Salt - a compound formed when the negative ions from an acid combine with the positive ions from a base.

Neutralization Reaction Acid + Base  Salt + Water

Common salts & uses

Titration Titration is the process in which a solution of known concentration (standard solution) is used to determine the concentration of another solution.

Titration Video Clip

Natural Indicators Many natural substances are acid-base indicators. ex) red cabbage, radishes, roses

Soaps are are organic salts Soaps are are organic salts. The nonpolar organic chain of carbon atoms on one end and either a sodium or potassium salt of a carboxylic acid group at the other end  

Review Questions What is the neutralization reaction?

Review Questions What is the neutralization reaction? Acid + Base  Salt + Water

Review Questions A compound formed when the negative ions from an acid combine with the positive ions from a base is called a __________.

Review Questions A compound formed when the negative ions from an acid combine with the positive ions from a base is called a salt.

Review Questions (T/F) Many natural substances are acid-base indicators.

Review Questions (T/F) Many natural substances are acid-base indicators. True

Review Questions __________ is the process in which a solution of known concentration (standard solution) is used to determine the concentration of another solution.

Review Questions Titration is the process in which a solution of known concentration (standard solution) is used to determine the concentration of another solution.

Review Questions A chemical reaction between an acid and a base that takes place in a water solution is called a(n) __________.

Review Questions A chemical reaction between an acid and a base that takes place in a water solution is called a(n) neutralization reaciton.