Post on 20-Dec-2015
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)