Week 11 Redox Reactions PDF

Redox (Reduction- Oxidation) Reactions  Importance https://www.youtube.com/watch?v=Doxrn05t08U  Charges to Memorize All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K :...

Redox (Reduction- Oxidation) Reactions  Importance https://www.youtube.com/watch?v=Doxrn05t08U  Charges to Memorize All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O , S and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has 2+ or 3+ charges  Examples All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has Indicate 2+ the or 3+(oxidation charges charges states) of the elements in H 2O H2O has 2 H and 1 O and the total charge of H 2O is zero Each H has 1+ charge , so 2 H+ = 2+ charge Each O has 2- charge, so 1 O has 2- charge Thus, the total charge of H2O is 2x1 -2 = 0  Examples All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has 2+ or 3+ charges What is the oxidation state (charge) of Manganese atom in KMnO4 K + Mn + 4x O = 0 1 + Mn + 4x(-2) = 0 => 1+ Mn -8 = 0  Mn= 7 => Mn7+  Examples All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has 2+ or 3+ charges What is the oxidation state (charge) of Nitrogene atom in NO - 3 N + 3x O = -1 N + 3x(-2) = -1 N= 5  Examples All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has 2+ or 3+ charges What is the oxidation state (charge) of Carbon atom in CO 2- 3 C + 3x O = -2 C + 3x(-2) = -2 C= 4  Examples All atoms have 0 charge when it is own (C (s) , Cu (s), O2 (g), H2 (g), Cl2 (g) ….. ) Atoms have charges when they are in the compounds: H, Li, Na and K : 1+ charge O and SO4 : 2- charge (Except H2O2) where the oxygen has 1- charge NO3, F, Cl, Br and I : 1- charge Ca, Mg, Zn: have 2+ charges Fe has 2+ or 3+ charges What is the oxidation state (charge) of Carbon atom in CO 2 C +2 x O = 0 C + 2x(-2) = 0 C=4  Redox Reactions Investigate the reaction below, find the oxidation states and indicate reduction and oxidation reactions. 2Fe (s) + O2 (g) ===> 2FeO Lets investigate the half reactions: 2 Fe0 ===> 2 Fe2+ + 4e- (Oxidation reaction) => Fe was oxidized - 2 O0 + 4e ===> 2 O2- (Reduction reaction) => O was reduced Fe reduced O so Fe is a reducing agent in this reaction O oxidized Fe so, O is a oxidizing agent in this reaction  Examples to Redox Reactions Cr (s) + 2 HCl (aq.) → CrCl2 (aq.) + H2 (g) Cr0 ====> Cr2+ + 2e- (Oxidation half reaction) => Cr was oxidized 2 H+ + 2e- ====> 2H0 (Reduction half reaction) => H was reduced Cr reduced H, so Cr is a reducing agent in this reaction.  Examples to Redox Reactions MnO2 (s) + 4 HCl (aq.) → MnCl2 (aq.) + Cl2 (g) + 2 H2O (l) Mn4+ + 2 e - ===> Mn 2+ (Reduction half reaction) => Mn was reduced 2Cl - ===> 2Cl0 + 2e - (Oxidation half reaction) => Cl was oxidized Mn oxidized Cl, so Mn is an oxidizing agent in this reaction