Acids and Bases continued

Which of the following is a strong acid? Hydrofluoric acid 2.Chloric acid 3.Sulfurous acid 4.Hydrobromic acid 5.Acetic acid

Gas- Forming Exchange Reaction

Reaction of Metal Carbonates with Acids CaCO 3(s) + 2CH 3 COOH (aq)  Ca(CH 3 COO) 2(aq) + H 2 CO 3(aq) H 2 CO 3(aq)  H 2 O (l) + CO 2(g) Carbonic acid is unstable and releases carbon dioxide gas Total Ionic Equation: CaCO 3(s) + 2CH 3 COOH  Ca CH 3 COO - + H 2 O + CO 2(g) Net Ionic Equation is the same

Reaction of Metal Sulfites and Sulfides with Acids CaSO 3(s) + 2HCl (aq)  CaCl 2(aq) + H 2 SO 3(aq) H 2 SO 3(aq)  H 2 O + SO 2(g) Net Ionic Equation: CaSO 3(s) + 2H + (aq)  Ca 2+ (aq) + H 2 O (l) + SO 2(g) Na 2 S (aq) + 2HCl (aq)  2NaCl (aq) + H 2 S (g) Net Ionic Equation: S 2- (aq) + 2H + (aq)  H 2 S (g)

Which of the following is a gas forming reaction? Na 2 CO 3 +Ba(OH) 2  2.AgNO 3 +Na 2 S  3.ZnCO 3 +HNO 3  4.HCl+CuSO 4 

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

O xidation I s L oss R eduction I s G ain Mn (s) + O 2 (g)  MnO 2 (s) Manganese is oxidized 4 e - Mn 4+ (O 2- ) 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 NO 2 (or sometimes NO) 4HNO 3(aq) +Cu (s)  Cu(NO 3 ) 2(aq) +2NO 2(g) +2H 2 O (l) -2 e - +2 e -

Which species is the reducing agent in the Cu + HNO 3 reaction? Cu 2.NO 2 3.Cu(NO 3 ) 2 4.HNO 3 5.H 2 O

Copper Oxide and Hydrogen Gas 2Cu+O 2  2CuO 2CuO+2H 2  2Cu+2H 2 O

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 CuCl 2 Cu is +2, Cl is -1, the actual charges SCl 2 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 H 2 SO 4 ? 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 HNO 3 ?

Oxidation State What is the oxidation state of Cr in Cr 2 O 7 2- ? O  -2 ion, thus sum equals charge = -2 7O  7  -2 = = 2 × Cr + (-14) 2 × Cr = +12 Cr = +6

What is the oxidation number of Br in BrF 4 + ?

Recognizing Redox Reactions

Which of the following is a redox reaction? CaCO 3  CaO+CO 2(g) 2.HNO 3 +KOH  KNO 3 +H 2 O 3.BaCl 2 +H 2 SO 4  BaSO 4(s) +2HCl 4.Ca+2H 2 O  Ca(OH) 2 +H 2(g) 5.Na 2 S+2HCl  2NaCl+H 2 S (g)

Metal + Acid Displacement

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 H 2 from acids top to bottom

Potassium + Water

Activity Series of Metals Zn (s) + CuSO 4(aq)  ZnSO 4(aq) + Cu (s) Cu (s) + 2AgNO 3(aq)  Cu(NO 3 ) 2(aq) + 2Ag (s) Fe (s) + 2HCl (aq)  FeCl 2(aq) + H 2(g) Zn (s) + 2HBr (aq)  ZnBr 2(aq) + H 2(g)

Metal + Metal Salt Displacement

Which of the following reactions does NOT happen? Cu (s) +H 2 SO 4(aq)  CuSO 4(aq) +H 2(g) 2.2HNO 3(aq) +2K (s)  2KNO 3(aq) +H 2(g) 3.FeCl 2(aq) +Zn (s)  ZnCl 2(s) +Fe (s) 4.Ca (s) +2H 2 O (l)  Ca(OH) 2(aq) +H 2(g) 5.Cu (s) +2AgNO 3(aq)  2Ag (s) +Cu(NO 3 ) 2(aq)