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Acids and Equilibrum

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Acids and Equilibrum Chapters 16-17 – PowerPoint PPT presentation

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Title: Acids and Equilibrum


1
Acids and Equilibrum
Chapters 16-17
2
  • Acids

3
A. Properties
ACIDS
BASES
  • electrolytes ? electrolytes
  • sour taste
  • bitter taste
  • turn litmus red
  • turn litmus blue
  • react with metals to form H2 gas
  • slippery feel
  • vinegar, milk, soda, apples, citrus fruits
  • ammonia, lye, antacid, baking soda

ChemASAP
4
The Arrhenius Model
  • Acid produces hydrogen ions in aqueous solution
  • Base produces hydroxide ions in aqueous
    solution

5
Acids
  • Acids have Hydrogen atom in them
  • Give off H
  • Examples
  • HCl
  • H2SO4
  • Even H2O

HCl ? H Cl-
H2SO4 ? 2H SO4-2
H2O ? H OH-
6
Bases
  • Have OH (Called hydroxide) in them
  • Examples
  • NaOH
  • Ca(OH)2
  • Even H2O

NaOH ? Na OH-
Ca(OH)3 ? Ca 2OH-
H2O ? H OH-
7
The Bronsted-Lowry Model
  • Acid proton donor
  • Base proton acceptor
  • The general reaction for an acid dissolving in
    water is

8
The Bronsted-Lowry Model
  • Conjugate acid-base pair

Always in pairs acids need a base to accept
proton.
9
The Bronsted-Lowry Model
  • Water acts as a base accepting a proton from the
    acid.
  • Forms hydronium ion (H3O)

10
Water is amphoteric
  • Can act as both acid and base
  • Can produce both H
  • And also OH-

11
Monoprotic and Polyprotic
  • Monoprotic - Give off only one H
  • HCl
  • HNO3
  • even HC2H3O2
  • Polyprotic - Give off more than one H
  • H2SO3

12
Acid Strength
  • Strong acid completely ionized or completely
    dissociated

13
Strong Acid
  • HCl ? H Cl-
  • Mostly H Cl- ions
  • Very little HCl molecule in solution.

14
Strength
  • Strong Acid/Base
  • 100 ionized in water
  • strong electrolyte

HCl HNO3 H2SO4 HBr HI HClO4
NaOH KOH Ca(OH)2 Ba(OH)2
15
B. Acid Strength
  • Weak acid most of the acid molecules remain
    intact

16
Acid Strength
  • Common strong acids are
  • Sulfuric acid, H2SO4
  • Hydrochloric acid, HCl
  • Nitric acid, HNO3
  • Perchloric acid, HClO4

17
Strength
  • Weak Acid/Base
  • does not ionize completely
  • weak electrolyte

HF CH3COOH H3PO4 H2CO3 HCN
NH3
18
Strong and Weak
  • Strong and weak are not the same as Concentrated
    and dilute
  • Strong means
  • Concentrated means

Can a concentrated acid solution be weak?
19
Water as an Acid and a Base
  • Water is amphoteric it can behave as either an
    acid or as a base
  • Ionization of water
  • Concentration of hydronium and hydroxide are
    equal

20
Acids and Bases
21
PH
  • Used to measure strength of an Acid or Base

22
The pH Scale
  • The p scale is used to express small numbers.
  • pH ?log H

23
The pH Scale
24
The pH Scale
  • Because the pH scale is a log scale based on 10,
    the pH changes by 1 for every power of 10 change
    in the H.

25
B. pH Scale

0
14
7
INCREASING ACIDITY
INCREASING BASICITY
NEUTRAL
pH -logH3O
26
pH Scale
  • pH of Common Substances

27
pH Scale
pH -logH3O pOH -logOH- pH pOH 14
28
pH Scale
  • Lower the pH means STRONGER the acid
  • This means more H ions in solution
  • This is the ion that makes acid act like an acid
  • Each one unit change is 10 times stronger

29
A. The pH Scale
30
B. pH Scale
  • What is the molarity of HBr in a solution that
    has a pH of 4.4?

Acidic
pH -logH 4.4 -logH -4.4
logH H3O 4.0 ? 10-5 M HBr
31
Measuring pH
  • Indicators substances that exhibit different
    colors in acidic and basic solutions

32
Universal Indicator
33
Measuring pH
  • Other methods
  • Indicator paper
  • pH meter

34
Mixing an acid and a base
  • Neutralization Reaction

Acid Base ? Water and salt HCl NaOH
? H2O NaCl
neutral
Strong Acid Strong Base Strong Acid Weak
Base Weak Acid Strong Base Weak acid
weak base
slightly acidic
slightly basic
neutral
35
Acid-Base Titrations
  • Titration delivering a measured volume of a
    solution of known concentration into the solution
    being analyzed
  • Titrant a standard solution
  • Buret device used for accurate measurement of
    the delivery of a liquid
  • Stoichiometric point (equivalence point) when
    just enough titrant has been added to react with
    all of the solution being analyzed

36
Acid-Base Titrations
  • Titration curve (pH curve) plot of the data (pH
    vs volume) for a titration

37
Buffered Solutions
  • Buffered solution resists a change in its pH
    when either and acid or a base has been added
  • Presence of a weak acid and its conjugate base
    buffers the solution
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