Acids, Bases and Salts Acid-Base Theories CHAPTER 15 PA 530-538.
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Transcript of Acids, Bases and Salts Acid-Base Theories CHAPTER 15 PA 530-538.
Acids, Bases and Salts
Acid-Base Theories
CHAPTER 15
PA 530-538
What is an Acid?
The term acid comes from the Latin term acere, which means "sour".
ex. Lemon juice, vinegar, and many other foods taste sour.
Acids Bases
• Taste sour • Corrosive • React with some
metals to produce H2
• Change Litmus to red acid= red
• React with bases to form water and salt.
• Bases taste bitter• Feel slippery• Corrosive• Change Litmus to
blue base = Blue• Become less
basic when mixed with acids.
Always Use Ref. Tables
(vinegar)
Table L Common Bases
• Formula Name
• NaOH(aq) sodium hydroxide• KOH(aq) potassium hydroxide• Ca(OH)2(aq) calcium hydroxide• NH3(aq) aqueous ammonia
Svante Arrhenius 1859 - 1927
Swedish chemist, proposed theories of electrolytic disassociation (acids/bases)
and greenhouse effect.
Arrhenius Theory of Acids & Bases
Acid - produces hydrogen ion (H+) in a solution.
HA H+ + A¯
Base – produces hydroxide ion (OH¯) in a solution.
XOH X+ + OH¯
Nature of the Hydrogen Ion or Proton
• Proton is so small that does not exist isolated in water.
• H+ + H2O H3O +
• Hydronium Ion
Nature of Hydroxide Ion
• The presence of OH- makes the substance an electrolyte and a base.
• Alcohols contain the OH group but are NOT IONIC COMPOUNDS therefore alcohols are NOT bases.
• C H O are molecular compounds NOT ionic compounds!!!!
HOW TO NAME ACIDS
• NO OXYGEN IN FORMULA
• HYDRO ----- ACID
HCl Hydrochloric acid
HBr Hydrobromic acid
HF Hydrofluoric acid
H2S Hydrosulfuric acid
• OXOA CIDS • CONTAIN OXIGEN IN
FORMULA• ENDING
• OUS if ion ends ITE
• IC if ion ends in ATE• Use table E
Solutions of Ionic Compounds conduct electricity = Electrolytes
Electrolytes – ions (charged particles) in solution.
HCl(aq) H+ + Cl-
HydrochloricAcid
H+ Cl -
Solutions
; Release OH- (aq)
Metal (+) and Non-Metal (-)
Electrolytes – conduct electricity when dissolved in H2O
Solutions= Salts (ionic), acids, & bases
Salts = ionic (+) (-)
Strong Acid & Base
Weak Acid or
Weak Base
Covalent = no ions
bright dim dark
Conductivity apparatusElectrolytes – conduct electricity
when dissolved in water
STRONG ACIDS
• COMPLETELY DISSOCIATED
• If the solution is 2 M, 2 mol of H + and 2 mol of Cl-
WEAK ACIDS
• Partially dissociated. Molecules stay together and only some of them dissociate.
HI
HBr
HCl
HNO3
H2SO4
HClO4
LiOH
NaOH
KOH
RbOH
CsOH
Naming Acids
Binary Acids- composed of hydrogen + 1 other element
Ex. HCl Hydrochloric Acid
Binary Acids begin with “hydro -”followed by name of other element; modified with an ending of “-ic”
Ternary Acids - molecular (covalent)- composed of hydrogen + oxygen containing polyatomic ion (Ref. E)
Ex. HNO3 Nitric Acid (NO31- Nitrate ion)
HNO2 Nitrous Acid (NO21- Nitrite ion)
H2SO4 Sulfuric Acid (SO42- Sulfate ion)
Ternary Acids = Anion suffix (-ate or -ite) is dropped and replaced with “-ic” or “-ous” respectively.
TABLE M common acids
• HCl(aq) hydrochloric acid• HNO3(aq) nitric acid
• H2SO4(aq) sulfuric acid
• H3PO4(aq) phosphoric acid
• H2CO3(aq) carbonic acid
• CH3COOH(aq) ethanoic acid
• HC2H3O2(aq) (acetic acid)
Common Acids – Ref. KNitric acid (HNO3)1) Most is used to make fertilizer
2) Well known for making explosives
Hydrochloric acid (HCl)1) Most is used to clean metals (pickling)
2) Also called muriatic acid
Sulfuric acid (H2SO4) 1) The most widely used chemical in the world
2) Most of it is used to make fertilizer
3) It is a good dehydrating agent
4) It is used in car batteries
Properties of Bases1) Bases feel slippery
2) Bases are electrolytes
3) Bases are corrosive, poisonous, and can cause severe burns (Lye = conc. NaOH)
4) Bases turn litmus blue; Blue = Base
5) Bases = pH greater than 7
Big in Base
6) Bases neutralize acids
Common Bases – Ref. LAmmonia NH3 1) The most widely used base
2) Used in household cleaning materials
3) Used as fertilizer; adds nitrogen to soil
Calcium hydroxide (caustic lime) Ca(OH)2 1) Used to make mortar and plaster
2) Used to help neutralize acid soil
Sodium hydroxide (Lye) NaOH1) One of the strongest bases
2) Used in oven cleaners and drain cleaners
Always Use Ref. TablesAcids ending = “- ic”
Bases = Metal + hydroxide
(vinegar)
Reactions of Acid with metals
• Use table J!• Metals above H2 in table J react with acids
by a single replacement reaction producing H2.
• 2 HCl + Zn H2 + ZnCl2
Neutralization Reaction
Acids and bases react to neutralize each other, forming water and a salt:
Acid + Base Water + Salt
HA + XOH H2O + XA
Double Replacement Reaction
Titration• Is a process that uses a neutralization to
determine the concentration of an acid or a base. Concentration in molarity is the amount of moles of solute per liter of solution. When the reaction of neutralization is 1:1 we use the following formula in a titration
•Ma x Va = Mb x V b
Vocabulary• Standard solution : the solution of known
molarity• Buret : instrument to measure exact
volumes of liquids• Erlenmeyer Flask • Indicator : a substance that changes color in
the presence of an acid or base.• End point: when the amount of H+ = OH-
At the end point
•Ma x Va = Mb x V b
Base
OH -
Acid
H +
Acid – Base Titration
Erlenmeyer flask
Two Burets with valves at bottom.
Record vol. in mL (twice)
Color indicator =
phenolphthalein
What is pH ?
pH is the negative logarithm of the hydrogen ion concentration =
pH = - log [H+]
Remember that sometimes H+ is written H3O
+, so
pH = - log [H3O+]
means the same thing.
pH Scale = log (base 10) scale
An increase of 1 in pH corresponds to a decrease of a factor of 10 in H+ concentration.
pH is.. Big in Base & Blue
Typical pH Values
of CommonMaterials
Oven Cleaner / Drain Cleaner
Hair Remover
Baking Soda
Soap
Ammonia (NH3)
Lemon Juice
Coffee / Tea
Blood
Battery Acid
Saliva
Pure WaterSeawater
Stomach Acid
Milk
Vinegar, Soft Drinks
Tomatoes
Bas
icA
cid
icNeutral
More about pH
Kw = dissociation constant for water = 10-14
1 x 10-14 = [H+] x [OH-]
= [ 10-7 ] x [ 10-7 ]
A neutral solution has a pH of 7.
[H+] = [OH-] = 1 x 10-7 M
pH and [H+]
If pH is… [H+] = ??
pH = 8 _____
pH = 12 _____
pH = 6 _____
pH = 2 _____
Finding pH for a solution of a strong acid or strong base
• For strong acid the concentration of the acid is the same as H+
• For strong bases the concentration of the base is the same as OH-.
Find the pH for
• A) 0.0001 M HCl• B) 0.01 M HBr• C) 0.001 M NaOH
Acid-Base Indicators
• A substance that have different colors at different pH.
Always Use Ref. Tables
(vinegar)
Bronsted Lowry definition
• An ACID is a substance that donates H+
• A BASE is a substance that ACCEPTS H+
P 177 REVIEW BOOK
1) 2
2) 1
3) 1
4) 2
5) 4
6) 4
7) 1
8) 3
9) 2
10)2
11) 4
12)1
13)1
P 181 Review Book
17)4
18)1
19)2
20)4
21)1
22)4
23)4
24)1
25)4
26)4 35)4
27)1 36)3
28)4
29)1
30)4
31)2
32)3
33)4
34)1
P 185 answers
40)4
41)2
42)2
43)1
44)4
45)2
46)25 ml
47)3000ml
48)20mL
49)50mL
50)6M
P 178 rb answers
• 14. chlorate• 15 a) hydrosulfuric acid• b) hydrobromic acid• c) lithium hydroxide• d) magnesium hydroxide• 16. An electrolyte can also be a base or a
salt. An indicator can be added to test if is an acid or a base.
Page 187 answers
61)4
62)1
63)3
64)3
65)3
66)2
67)1
68)1
69)4
70)2
71)Bromocresol green
72)Bet 5.4 and 6
73)A blue
yellow
74) B
75) 1
Handout Answers
1) 2
2) 2
3) 4
4) 2
5) 3
6) 3
7) 4
• pH=6• Methyl orange/
Bromthymol blue• Bromocresol green