Title: Ox always change during redox reactions:
1Oxidation Numbers Redox Reactions
- Ox always change during redox reactions
- Increase Ox Oxidation
- Decrease Ox Reduction
Its a redox reaction if element ?
compound or compound ? element
S8(s) 8 O2(g) ? 8 SO2(g)
Ox(S) 0 ? 4 (oxidized lost e- increased
Ox) Ox(O) 0 ? -2 (reduced gained e-
decreased Ox)
2Oxidation Numbers Redox Reactions
A more complex example
Cu is oxidized (Ox ? loss of e-). H is
unchanged. O is unchanged. N is reduced (Ox ?
gain of e-).
3Oxidation Numbers Redox Reactions
Exchange reactions are not redox no change in
oxidation state occurs.
Pb(NO3)2(aq) 2 Kl(aq) ? 2 KNO3(aq) Pbl2(s)
4Displacement Reactions
Redox
Fe(s) CuSO4(aq) ? FeSO4(aq) Cu(s) 0
2 2 0
Cu(s) 2 AgNO3(aq) ? Cu(NO3)2(aq) 2 Ag(s)
0 1 2 0
Not all metals can displace another from its
salts Cu(s) ZnSO4(aq) no reaction
An activity series was developed
5Activity Series of Metals
Displace H2 from H2O (l), steam or acid
Displace H2 from steam or acid
Ease of oxidation decreases
Displace H2 from acid
No reaction with H2O, steam or acid
6Displacement Reactions
- Powerful reducing agents at the top.
Higher elements displace lower ones Zn(s)
CuSO4(aq) ? ZnSO4(aq) Cu(s) Mg(s) 2
HCl(aq) ? MgCl2(aq) H2(g)
- Metals at the bottom are unreactive.
- Coinage metals
- Their ions are powerful oxidizing agents.
7Displacement Reactions
8Displacement Reactions
2 Na(s) 2 H2O(l) ? 2 NaOH(aq) H2(g)
9(No Transcript)
10pH Scale
- In pure water, a few molecules ionize to form
H3O and OHH2O H2O ? OH H3O - In acidic and basic solutions, these
concentrations are not equalacidic H3O gt
OHbasic OH gt H3Oneutral H3O
OH
11pH Scale
- Measure how much H3O is in a solution using pH
- pH lt 7.0 acidic
- pH gt 7.0 basic
- pH 7.0 neutral
- Measure of H3O and OH concentration (moles per
liter) in a solution - As acidity increases, pH decreases
12pH Scale
- The pH scale is logarithmic100 102 log(102)
210 101 log(101) 11 100 log(100)
00.1 101 log(101) 10.01 102 log(102)
2 - pH log H3O
- pH if H3O 105? 109? Acidic or basic?
- pH if H3O 0.000057 M?
13Finding H3O from pH
- H3O 10-pH
- What is H3O if pH 8.9?
14pH Quantitative Measure of Acidity
- Acidity is related to concentration of H (or
H3O) - pH -logH3O