Acids and Bases

continued

Which of the following is a strong acid?

100

0

130

Hydro

fluor

ic a

cid

Chloric

aci

d

Sulfu

rous

acid

Hydro

brom

ic a

cid

Acetic

aci

d

0% 0% 0%0%0%

1. Hydrofluoric acid

2. Chloric acid

3. Sulfurous acid

4. Hydrobromic acid

5. Acetic acid

Gas-Forming

Exchange Reaction

Reaction of Metal Carbonates with Acids

CaCO3(s) + 2CH3COOH(aq) Ca(CH3COO)2(aq) + H2CO3(aq)

H2CO3(aq) H2O(l) + CO2(g)

Carbonic acid is unstable and releases carbon dioxide gas

Total Ionic Equation:CaCO3(s) + 2CH3COOH Ca2+ + 2CH3COO- + H2O + CO2(g)

Net Ionic Equation is the same

Reaction of Metal Sulfites and Sulfides with Acids

CaSO3(s) + 2HCl(aq) CaCl2(aq) + H2SO3(aq)

H2SO3(aq) H2O + SO2(g)

Net Ionic Equation:

CaSO3(s) + 2H+(aq) Ca2+

(aq) + H2O(l) + SO2(g)

Na2S(aq) + 2HCl(aq) 2NaCl(aq) + H2S(g)

Net Ionic Equation:

S2-(aq) + 2H+

(aq) H2S(g)

Which of the following is a gas forming reaction?

100

0

130 0% 0%0%0%

1. Na2CO3+Ba(OH)2

2. AgNO3+Na2S

3. ZnCO3+HNO3

4. HCl+CuSO4

Oxidation-Reduction Reactions

Oxidation-Reduction Reactions

Oxidation –loss of electrons

Reduction – gain of electrons

Oxidation and Reduction always occur together

oxidizing agent – substance that causes oxidation

reducing agent – substance that cause reduction

Oxidation Is Loss

Reduction Is Gain

Mn (s) + O2 (g) MnO2 (s)

Manganese is oxidized

4 e- Mn4+(O2-)2

Common Oxidizing and Reducing Agents

Copper and Nitric Acid

Nitric acid is a powerful oxidizing agent

• The nitrogen in the nitric acid is reduced to NO2 (or sometimes NO)

• 4HNO3(aq)+Cu(s) Cu(NO3)2(aq)+2NO2(g)+2H2O(l)

-2 e-

+2 e-

Which species is the reducing agent in the Cu + HNO3 reaction?

100

0

130

CuNO2

Cu(NO

3)2

HNO3

H2O

0% 0% 0%0%0%

1. Cu

2. NO2

3. Cu(NO3)2

4. HNO3

5. H2O

Copper Oxide and Hydrogen Gas

2Cu+O2 2CuO 2CuO+2H2 2Cu+2H2O

Oxidation Numbers

• To keep track of the movement of electrons in reactions we assign oxidation numbers to each element. Treat all interactions as ionic and assign electrons to the most electronegative element to give it its usual charge.

• Sometimes real but usually not.

Oxidation Number Rules

• All pure elements have Ox# = 0

• Monatomic ions have Ox# = charge

• Hydrogen is +1 unless with a metal then -1

• Fluorine is -1 in all compounds

• Oxygen is -2 unless attached to fluorine or itself H-O-O-H both O’s are -1

• Other halogens are -1 unless attached to F or O

Binary compounds

• CuCl2 Cu is +2, Cl is -1, the actual charges

• SCl2 Cl is assigned -1

• Neutral compound so sum of ox# = 0

• S + 2 × (-1) = 0, S is +2, assigned charge

Finding Oxidation Numbers

What is the oxidation number of S in H2SO4?

• H +1

• O -2

• neutral compound, thus sum equals zero

• 4O 4 -2 = -8

• 2H 2 +1 = +2

• 0 = +2 + S + (-8)

S = +6

What is the oxidation number of N in HNO3?

100

0

130

7 6 5 4 3

0% 0% 0%0%0%

1. +7

2. +6

3. +5

4. +4

5. +3

Oxidation State

What is the oxidation state of Cr in Cr2O72-?

• O -2

• ion, thus sum equals charge = -2

• 7O 7 -2 = -14

• -2 = 2 × Cr + (-14)

• 2 × Cr = +12

• Cr = +6

What is the oxidation number of Br in BrF4

+?

100

0

130

7 6 5 4 3

0% 0% 0%0%0%

1. +7

2. +6

3. +5

4. +4

5. +3

Recognizing Redox Reactions

Which of the following is a redox reaction?

100

0

1300% 0% 0%0%0%

1. CaCO3CaO+CO2(g)

2. HNO3+KOHKNO3+H2O

3. BaCl2+H2SO4BaSO4(s)+2HCl

4. Ca+2H2OCa(OH)2+H2(g)

5. Na2S+2HCl2NaCl+H2S(g)

Metal + Acid Displacement

Activity Series of Metals

Activity Series of Metals

• metals higher in series react with compounds of those below

• metals become less reactive to water top to bottom

• metals become less able to displace H2 from acids top to bottom

Potassium + Water

Activity Series of Metals

Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s)

Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

Fe(s) + 2HCl(aq) FeCl2(aq) + H2(g)

Zn(s) + 2HBr(aq) ZnBr2(aq) + H2(g)

Metal + Metal Salt Displacement

Which of the following reactions does NOT happen?

100

0

1300% 0% 0%0%0%

1. Cu(s)+H2SO4(aq)CuSO4(aq)+H2(g)

2. 2HNO3(aq)+2K(s)2KNO3(aq)+H2(g)

3. FeCl2(aq)+Zn(s)ZnCl2(s)+Fe(s)

4. Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

5. Cu(s)+2AgNO3(aq)2Ag(s)+Cu(NO3)2(aq)