1. Acids and Bases

2. What are we going to discuss?
Tables K and L in the Reference Tables list a few of the most common Acids and Bases, but what are Acids and Bases.
Acids and Bases are classes of compounds that can be recognized by their easily observed properties.
In this unit will learn about these properties, the definitions that are used to explain these properties, and the important reactions that occur between acids and bases.

3. Properties of Acids
Electrolytes, or break up into ions when aqueous, conduct electricity in aqueous solutions
Strong acid: good conductor
Weak acid: poor conductor
Sour Taste; citric acid and acetic acid
React with most metals to produce H2 (g)
React with bases to form H2O and salt
React with indicators to change color
turn litmus red
phenolphthalein turns colorless
pH values are
see Table M for others

4. Properties of Bases
Electrolytes conduct electricity in aqueous solutions
Strong base: good conductor
Bitter Taste; caustic, feel slippery (soap)
React with acids to form H2O and salt
React with indicators to change color
litmus turns blue
phenolphthalein turns pink
--pH values are

5. Arrhenius’ Theory on Acids and Bases
Arrhenius Acid
Definition: a substance that ionizes in water to give hydrogen ions (proton) or a Hydronium ion: H+ or H3O+
Ex: Hydrochloric acid, HCl (a strong acid).
HCl (g) H+ (aq) + Cl- (aq)
ACIDIC solutions are formed when an acid transfers a proton to water.

6. Hydronium Ion
The H+ interacts strongly with a lone pair of electrons on the oxygen of a water molecule. The resulting ion, H3O+ is called the hydronium ion.
Ex: HCl + H2O H3O+1 + Cl-1

7. Arrhenius’ Bases
Definition: a substance that ionizes in water to give hydroxide ions: OH-
Example: NaOH, NH3
NaOH (s)  Na+(aq) + OH- (aq)
NH3 +H2O  NH4+1 + OH-

8. SALTS
A salt is an ionic compound that does not produce an H+ ion or OH- ion when dissolved in water.
Salts are not acids or bases they are neutral substances.
Ex.
NaCl
MgCl2

9. Naming Acids

10. Binary acids –two elements - H+ *
hydrogen _____ ide
becomes hydro_____ic acid
Hydro_____ic acid
Hydrochloric acid
Hydrofluoric acid
Hydrosulfuric acid
Hydrobromic acid
Hydrogen _____ ide
Hydrogen chloride
Hydrogen fluoride
Hydrogen sulfide
Hydrogen bromide

11. Ternary acids 3 elements: H+ and a polyatomic ion
Hydrogen _____ate becomes
_________ic acid
Hydrogen _____ate
Hydrogen sulfate
Hydrogen chlorate
Hydrogen nitrate
Hydrogen phosphate
_________ic acid
Sulfuric acid
chloric acid
nitric acid
Phosphoric acid

12. Hydrogen ________ite _________ ous acid
Hydrogen _____ite becomes
_______ous acid
_______ous acid
Nitrous acid
Sulfurous acid
Chlorous acid
Hydrogen _____ite
Hydrogen nitrite
Hydrogen sulfite
Hydrogen chlorite

13. Table K and Table L
These two tables list the most common acids and bases.
Table K lists the common acids, these acids are the major acids you will need to be familiar with.
The top 4 acids on table K are all strong acids while the last 2 are weak acids.
Table L lists common bases, these bases are the major bases you will need to be familiar with.
The top 3 bases on table L are strong bases while that last 1 is a weak base.

14. Strengths of Acids
Strong acids: ionize completely which means if 100 molecules dissolve in water all 100 will break up into ions
Examples:
HCl  H+ + Cl-
H2SO4  2H+ + SO4-2

15. Strengths of Acids
Weak acids: ionize slightly or only a small percentage will break up into ions
Example: acetic acid (vinegar)
CH3COOH  CH3COO- + H+
****note if an organic compound ends in COOH it’s a weak acid!!!

16. Strengths of Bases Strong bases: ionize completely Example:
NaOH  Na+ +OH-

17. Strengths of Bases Weak base: ionizes slightly Example: ammonia
NH3 + H2O  NH4+ + OH-

18. Acid and Base Reactions
You will need to be familiar with 2 reactions that involve acids and bases.
The first reaction only involves an acid with a metal.
The second reaction deals with reacting an acid with a base to produce a salt and water or neutralization.

19. Acids with metals
Some metals will replace the hydrogen in the acid and form hydrogen gas
Single Replacement Reaction (SRR)
Use Table J to decide if the metal is more reactive or to see if the reaction will work.
MgCl H2
Mg HCl

20. Neutralization Reaction
In a neutralization reaction an Acid will react with a base to produce salt and water.
Three ways we can express neutralization reactions:
Word equation
Formula equation
Net ionic equation
A net ionic equation has only the ions that have taken part in the reaction. In the reaction the ions that do not change are omitted, these ions are called spectator ions. See example

21. Neutralization acid + base water + a salt HCl + NaOH HOH + NaCl
Hydrochloric Acid + Sodium Hydroxide yields Water + Sodium Chloride
HCl NaOH
HOH NaCl
H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)
H2O + Na+(aq) + Cl-(aq)
H+(aq) + OH-(aq)
H2O
This is the net ionic equation for all neutralization reactions this equation shows how the ions are neutralized.

22. Try This One H2SO4 + 2NaOH 2H2O + Na2SO4
Sulfuric acid + sodium hydroxide yields water + sodium sulfate
H2SO NaOH
2H2O Na2SO4
2H2O + 2Na+ + SO4-2
2H+ + SO Na+ + 2OH-
H+ + OH-
H2O

23. Concentration of H+ in Acids
A. 1.0 M HCl (monoprotic acid)
HCl  H+ + Cl-
Produces 1 H+ so the concentration of H+ is 1.0 M
[H+] = 1.0 M

24. Concentration of H+ in Acids
B. 1.0 M H2SO4 (diprotic acid)
H2SO4  2H+ + SO4-2
Produces 2 H+ so the concentration of H+ is 2(1.0 M)
[H+] = 2.0 M

25. Concentration of OH- in Bases
A. 1.0 M KOH
KOH  K+ + OH-
Produces 1 OH- so the concentration of OH- is 1.0 M.
[OH-] = 1.0 M

26. Concentration of OH- in Bases
B. 1.0 M NaOH
NaOH  Na+ + OH-
Produces 1 OH- so the concentration of OH- is 1.0 M.
[OH-] = 1.0 M

27. Concentration of OH- in Bases
C. 1.0 M Ca(OH)2
Ca(OH)2  Ca+2 + 2OH-
Produces 2 OH- so the concentration of OH- is 2(1.0 M).
[OH-] = 2.0 M

28. Concentration of OH- in Bases
D. 1.0 M Mg(OH)2
Mg(OH)2  Mg+2 + 2OH-
Produces 2 OH- so the concentration of OH- is 2(1.0 M).
[OH-] = 2.0 M

29. Titration
An Acid-Base titration is a lab technique used find the unknown concentration of a specific volume for an acid or a base by neutralizing it with a specific volume of an acid or base of a known concentration.
During a titration you deliver known volumes of a base to a known volume of an acid until it is neutralized or just slightly basic.
This is also known as the endpoint of a titration.
End point: point at which the solution changes from acidic to “just” basic.
Using the Acid-Base titration formula listed on Table T you can solve for your unknown concentration.

30. MaVa = MbVb (Table T) Acid- Base Titrations Ma = molarity of H+
Acids and bases neutralize each other when the concentration of the H+ equals the concentration of the OH-.
MaVa = MbVb (Table T)
Ma = molarity of H+
Va = volume of acid
Mb = molarity of OH-
Vb = volume of base

31. Titration-Setup

32. Titrations (Neutralization) Problems
Ex. What volume of 0.50M HCl is required to neutralize 100mL of 2.0M NaOH?
MaVa = MbVb
Ma = .5M
Va = ??
Mb = 2.0M
Vb = 100mL
Plug in and solve
0.5(x) = 2.0(100)
X = 400mL HCl
Try the rest on your own!!!

33. Acidity and Alkalinity of Solutions
Although water is a covalently bonded substance it does ionize to a very small extent as shown by the equation below.
H2O   H+ + OH-
It can be seen that in pure water the [H+] = [OH-].
When one of the ion concentrations increases the other will decrease.

34. Acidity and Alkalinity of Solutions (continued)
So if you dissolve HCl in water the concentration of [H+] will increase and the [OH-] will decrease making the solution acidic.
When NaOH is dissolved in water the concentration of [OH-] increases and the [H+] decreases making the solution basic.
So when [H+] > [OH-] the solution is acidic and when [H+] < [OH-] the solution is basic.
The terms acidity and alkalinity (or basicity) refer to the strength of the acid or base in terms of H+ and OH- concentrations.

35. Summary of Aqueous Solutions
Autoionization of water
HOH H+ + OH-
In any aqueous [H+] x [OH-] = 1.0x10-14
Neutral Solution
[H+] = [OH-]
1.0x10-7M = 1.0x10-7M
Acidic Solution
[H+] > [OH-]
1.0x10-1M > 1.0x10-13M
Basic Solution
[H+] < [OH-]
1.0x10-13M < 1.0x10-1M

36. pH Scale
A scale, called the pH scale, has been developed to express [H+] as a number from 0 to 14.
A pH of 0 is strongly acidic, a pH of 7 is neutral, and a pH of 14 is strongly basic
The pH scale is logarithmic which means each change of a single pH unit signifies a tenfold change in the concentration of the [H+]

37. pH Scale (continued)
Thus a solution with a pH of 5 is ten times greater in [H+] than a solution with a pH of 6
Because the [H+] and [OH-] are directly related, a pH change of one unit represents a tenfold increase or decrease of both [H+] and [OH-]
As the concentration of the hydrogen ion increases the hydroxide ion concentration decreases and vice versa.

38. pH Scale

39. pH (continued) additional info about pH and [H+]
To calculate pH you can take the – log([H+]) for example if the [H+] = 1x10-2 the ph will he equal to – log (1x10-2) which calculates to a pH of 2.
Calculate the pH of the following solutions when given the [H+]
1. [H+] = 1x10-11
Ans: pH =11
2. [H+] = 1x10-4
Ans: pH =4
3. [H+] = 1x10-9
Ans: pH =9

40. Acid – Base Indicators
An indicator is a substance that changes its color when it gains or loses a proton or an H+ ion.
There are several different indicators and they change differently when exposed to different pH values.
On your reference tables there is a list of common acid base indicators that show the color changes at varying pH values
See Table M
You can use more than one indicator to estimate the approximate pH of an unknown substance from the color changes

41. An Additional Theory on the Definition of Acids and Bases
Another theory on acids and bases defines an acid as any substance that donates a proton or an H+ ion when dissolved in water.
For example HCl is an acid because it donates an H+ ion to H2O when it dissolves.
The theory also states that a base is any substance that accepts a proton or an H+ ion.
So in the same situation when HCl is dissolved in H2O the H2O acts as a base because it accepts an H+ ion and becomes H3O+
So in summary an acid can be any substance that donates an H+ ion or a proton and a base can be any substance that accepts the H+ ion or a proton.