Chapter 20
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Chapter 20. Acids and Bases. Section 20.1. Properties of Acids : Tart or sour taste (lemon juice) Electrolytic Both strong and weak Will cause indicators to change colors A metal + an acid will produce hydrogen gas Single replacement reaction Acid + Base → water + a “salt”

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Chapter 20

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Chapter 20

Chapter 20

Acids and Bases


Section 20 1

Section 20.1

  • Properties of Acids:

    • Tart or sour taste (lemon juice)

    • Electrolytic

      • Both strong and weak

    • Will cause indicators to change colors

    • A metal + an acid will produce hydrogen gas

      • Single replacement reaction

    • Acid + Base → water + a “salt”

      • Double replacement reaction

  • Acids:

    • Something that produces a hydrogen ion (H+) in solution


Chapter 20 2884639

  • Properties of Bases:

    • Bitter

    • Slippery (soap)

    • Electrolytic

      • Both strong and weak

    • Will cause an indicator to change colors

  • Base:

    • Something that produces a hydroxide ion (OH1-) in solution


Naming

Naming

  • HBr

    • Hydrogen with a single anion

    • Use prefix hydro- and suffix –ic

    • Hydrobromic acid

  • H2SO3

    • Hydrogen with a polyatomic that ends in –ite

    • Change suffix to –ous

    • Sulfurous acid

  • HNO3

    • Hydrogen with a polyatomic that ends in –ate

    • Change suffix to –ic

    • Nitric acid

  • Remember… “-ic, I -ate something gross!”

  • Know rules! (page 578, Table 20.1!!!)


Section 20 2

Section 20.2

  • Self-ionization of water:

    • Reaction in which 2 water molecules produce ions

    • H2O + H2O → OH- + H3O+

    • Also written as:

      • H2O ↔ H+ + OH-

    • The H3O+ and H+ represent hydrogen ions in solution.


Neutral solutions

Neutral Solutions

  • In pure water, the concentration of hydrogen ions is equal to the concentration of hydroxide ions

    • 1 x 10-7M

    • [H+] = [OH-]

      • (brackets represent concentration)

    • This represents a neutral solution.


Solutions

Solutions

  • In a solution, if the [H+] increases, the [OH-] decreases and vice versa.

  • Ion-product constant of water, Kw:

    • Kw = [H+] x [OH-] = 1 x 10-14M

  • Acidic Solution:

    • The [H+] is greater than [OH-].

    • Therefore, the [H+] is greater than 1 x 10-7M.

  • Basic Solution:

    • The is [H+] less than [OH-].

    • Therefore, the [H+] is less than 1 x 10-7M.

    • A.k.a. alkaline solutions


Problem

Problem

  • If the [H+] is 1 x 10-5M, is the solution acidic, basic, or neutral? What is the [OH-]?


Ph scale

pH Scale

  • The pH scale ranges from 0-14.

    • 0 = strongly acidic

    • 7 = neutral

    • 14 = strongly basic

  • pH = -log [H+]

  • What is the pH of a neutral solution?


Sample problems

Sample Problems

  • What is the pH of the following concentrations?

    • [H+] = 1 x 10-2M

    • [H+] = 1 x 10-9M

    • [H+] = 1 x 10-5M

  • As long as you have a 1 x 10 to some power, the pH is the exponent.


Other formulas and problems

Other Formulas and Problems

  • pOH = -log [OH-]

  • pH + pOH = 14

  • What is the pH of a solution with a [OH-] of 4.0 x 10-11M?

    • Two ways to solve:

      • 1. find pOH then subtract from 14

        Or

      • 2. Use Kw to find [H+] then find pH using –log function.


Flow chart of ph and poh

Flow Chart of pH and pOH

  • Use the map to help you get from any point A to any point B…

    pH = -log [H+]pH + pOH = 14pOH = -log [OH-]

    [H+] ↔pH ↔ pOH ↔ [OH-]

    Kw = [H+] [OH-] = 1 x 10-14M


More samples

More Samples

  • What is the [H+] of a solution with a pH of 3.7?

  • If the [H+] is 3.1 x 10-5M, what is the pH? What is the pOH? What is the [OH-]?


Section 20 3 other definitions of acids and bases

Section 20.3 – Other definitions of Acids and Bases

  • Arrhenius Acids and Bases:

    • Acid:

      • Hydrogen containing compound that ionize to yield a hydrogen ion in solution.

    • Base:

      • Compounds that ionize to yield a hydroxide ion in solution.


Br nsted lowry acids and bases

Brønsted – Lowry Acids and Bases

  • He felt the Arrhenius definition was too limiting.

    • Acids:

      • Hydrogen ion donor

    • Bases:

      • Hydrogen ion acceptor

    • Examples:

      • NH3 + H2O ↔ NH4+ + OH-

      • HCl + H2O ↔ H3O + + Cl-


Chapter 20 2884639

  • Conjugate Acids:

    • Particle formed when a base gains a hydrogen ion.

  • Conjugate Base:

    • Particle that remains when an acid has donated a hydrogen ion.

  • Example:

    • NH3 + H2O ↔ NH4+ + OH-

    • B A CA CB

    • HCl + H2O ↔ H3O + + Cl-

    • A B CA CB

  • Amphoteric:

    • Substance that can act as both an acid or a base.


  • Strong acids and bases

    Strong Acids and Bases

    • Strong Acids/Bases:

      • Those that ionize completely in solution.

        • Ex: HCl, NaOH

    • Weak Acids/Bases:

      • Those that only slightly ionize in solution.

        • Ex: NH3, Acetic Acid (vinegar)

        • Tooth decay is caused by the weak acid – lactic acid: C3H6O3


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