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14.1 Properties of Acids and Bases

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1 14.1 Properties of Acids and Bases
Chapter 14 Acids & Bases 14.1 Properties of Acids and Bases

2 Properties of Acids Aqueous solutions have a sour taste
Some acids react with active metals to release hydrogen: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) Acids react with bases to produce salts and water: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) Acids conduct electric current

3 Properties of Acids Acids change the color of acid-base indicators:
Blue litmus turns red Methyl orange turns red Have a pH of less than 7 Donate protons, H+ React with carbonates Neutralize bases


5 Review: Acids Nomenclature
Binary acids - acids that contain two different elements: hydrogen and one of the more-electronegative elements prefix "hydro-" Root of element name "-ic" ending example: HBr = hydrobromic acid Oxyacids - compounds of hydrogen, oxygen, and a third element, usually a nonmetal no prefixes


7 Some Common Industrial Acids
Sulfuric Acid Highest volume production of any chemical in the U.S. Used in the production of paper, fertilizers, petroleum refining & car batteries

8 Some Common Industrial Acids
Nitric Acid Used in the production of rubber, plastics, pharmaceuticals, fertilizers & explosives Nitric acid is a volatile acid – its reactive components evaporate easily Stains proteins yellow (including skin!)

9 Some Common Industrial Acids
Hydrochloric Acid Used in the pickling of steel Used to purify magnesium from sea water Used to correct swimming pool pH Part of gastric juice, it aids in the digestion of protein Sold commercially as “Muriatic acid”

10 Some Common Industrial Acids
Phosphoric Acid A flavoring agent in sodas Used in the manufacture of detergents & fertilizers Not a common laboratory reagent

11 Some Common Industrial Acids
Acetic Acid Concentrated “glacial” acetic acid used in the manufacture of plastics Used in making pharmaceuticals Acetic acid is the acid present in vinegar

12 Properties of Bases Aqueous solutions of bases have a bitter taste
Bases change the color of acid-base indicators Turns red litmus blue Turns phenolphthalein magenta/purple Dilute aqueous solutions of bases feel slippery Bases react with acids to produce salts and water Bases conduct electric current Are proton, H+, acceptors Have a pH value of greater than 7 Neutralize acids

13 Arrhenius Acids & Bases
A chemical compound that increases the concentration of hydrogen ions, H+, in aqueous solution Arrhenius Base A substance that increases the concentration of hydroxide ions, OH-, in aqueous solution Swedish Chemist

14 Aqueous Solutions of Acids
Acids are molecular compounds that ionize in solution HNO3 + H2O → H3O+ + NO3- H2SO4 + H2O → H3O+ + HSO4- H2O + HCl → H3O+ + Cl- Proton Donor Proton Acceptor

15 Ionization Equations Instead of:
HCl (g) + H2O (l) → H3O+ (aq) + Cl- (aq) Sometimes we write this: HA + H2O (l) → H3O+ (aq) + A- (aq) Or even this: HCl (aq) → H+ (aq) + Cl- (aq) Generic formulas Leave out water

16 Strength of Acids Strong acids completely ionize in solution. (100%)
Weak acids ionize only slightly and are weak electrolytes.(<5%)

17 Strong Acid Dissociation

18 Weak Acid Dissociation

19 Strength vs. Concentration
Strength refers to ionization in solution. Concentration refers to the amount of solute in solution. It is possible to have a concentrated solution of a weak acid or base. It is also possible to have dilute solution of a strong acid or base.

20 Organic Acids Organic acids all contain the “carboxyl” group, sometimes several of them. The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

21 Examples of Organic Acids
Citric acid in citrus fruit Malic acid in sour apples Deoxyribonucleic acid, DNA Amino acids, the building blocks of protein Lactic acid in sour milk and sore muscles Butyric acid in rancid butter

22 Aqueous Solutions of Bases
Ionic bases dissociate when placed in water: NaOH (s) + H2O (l) → Na+ (aq) + OH- (aq) Basic solutions are referred to as “alkaline” Molecular bases produce hydroxide ions through a reaction with water: NH3 (g) + H2O (l) → NH4+ (aq) + OH- (aq)

23 Strength of Bases Strength of ionic bases in related to solubility:
High solubility = strong base Low solubility = weak base Molecular bases tend to be weak regardless of solubility

24 Chapter 14 Acids & Bases 14.2 Acid-Base Theories

25 Bronsted-Lowry Acids & Bases
A molecule or ion that is a proton donor Bronsted-Lowry Base: A molecule or ion that is a proton acceptor ex: hydroxide ion is the acceptor portion of the ionic base, not the whole compound itself Bronsted-Lowry Acid-Base Reaction: A reaction in which protons are transferred from the acid to the base.

26 Types of Acids Monoprotic Acids: HC2H3O2 HCl Diprotic Acid: H2SO4
Can donate 1 H Monoprotic Acids: HC2H3O2 HCl Diprotic Acid: H2SO4 Triprotic Acids: H3C6H5O H3PO4 * Each successive proton is harder to remove! Can donate 2 Hs Can donate 3 Hs Polyprotic Acids

27 Lewis Acids & Bases Lewis Acid:
An atom, ion or molecule that accepts an electron pair to form a covalent bond Lewis Base: An atom, ion or molecule that donates an electron pair to form a covalent bond Lewis Acid-Base Reaction: The formation of one or more covalent bonds between an electron-pair donor and electron-pair acceptor. This definition can be applied to phases other than aqueous reactions.

28 Chapter 14 Acids & Bases 14.3 Acid-Base Reactions

29 Conjugate Acids & Bases
Conjugate Base The species that remains after an acid has given up its proton H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq) The stronger the acid, the weaker its conjugate base Acid Conjugate Base

30 Conjugate Acids & Bases
The species that is formed when a base gains a proton H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq) The stronger the base, the weaker its conjugate acid Base Conjugate Acid

31 Proton-Transfer Reactions
These reactions favor the production of the weaker acid and the weaker base.

32 Amphoteric Compounds Any species that can act as either an acid or a base Ex: Water as a base: H3PO4 (aq) + H2O (l) ↔ H3O+ (aq) + H2PO4- (aq) Ex: Water as an acid: NH3 (g) + H2O (l) ↔ NH4+ (aq) + OH- (aq)

33 Hydroxyl Group in Molecules
The –OH group in a molecule can be acidic or amphoteric As the number of oxygens that are bonded around the atom with the –OH group increases, so does the acidity of the compound. Oxygens pull electron density away from the hydrogen, making it appear more positive (and attractive to water and other bases)

34 Bases Neutralize Acids
Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH)2 MgCl2 + 2 H2O

35 Acids Neutralize Bases
HCl + NaOH  NaCl + H2O Neutralization reactions ALWAYS produce a salt and water.

36 Acids React with Carbonates
2HC2H3O2 + Na2CO3 2 NaC2H3O2 + H2O + CO2

37 Neutralization Reactions
The reaction of hydromium and hydroxide ions to form water molecules Steps: Dissociation of a base in water Acid donates a proton to water Complete ionic equation Net ionic equation (no spectator ions)

38 Neutralization HCl + NaOH → NaCl + H2O

39 Products of Neutralization
HCl + NaOH  NaCl + H2O H2SO4 + Ca(OH)2  CaSO H2O HNO3 + KOH  KNO3 + H2O The products of neutralization are always a ______ and _______. salt water

40 Acid Rain SO3 (g) + H2O (l) → H2SO4 (aq) Formation of Acid Rain:
SO2, SO3, CO2, NO, NO2 Formation of Acid Rain: Nonmetallic oxides enter the atmosphere as a result of burning coal, auto exhaust and other forms of air pollution. Nonmetallic oxides in the air then combine with water to form oxyacids: SO3 (g) + H2O (l) → H2SO4 (aq)

41 Effects of Acid Rain on Marble (calcium carbonate)
George Washington: BEFORE George Washington: AFTER CaCO3 (s) + 2H3O+ (aq) → Ca+2 (aq) + CO2 (g) + 3H2O (l)

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