New Jersey Center for Teaching and Learning AP Chemistry - PDF document

Slide 1 / 83 Slide 2 / 83 New Jersey Center for Teaching and Learning AP Chemistry Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written Unit 3: Presentation E permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to Redox Reactions make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Click to go to website: www.njctl.org www.njctl.org Slide 3 / 83 Slide 4 / 83 REDOX Reactions Oxidation and Reduction REDOX reactions involve the transfer of electrons from one species to another. The substance that gains electrons is said to be reduced while the substance that loses electrons is said to be oxidized . Cu (s) + Ag +(aq) --> Cu +(aq) + Ag (s) In this reaction, a copper atom loses an electron to a silver Photosynthesis is a classic REDOX reaction where electrons ion. are transferred from water to carbon dioxide to create a new Cu(s) got oxidized sugar molecule. Ag + (aq) got reduced Slide 5 / 83 Slide 6 / 83 Oxidation and Reduction Oxidation States In order to determine whether a substance got oxidized or reduced Oxidation Reduction in a reaction, the oxidation state of each species must be known. Loses electrons (LEO) gains electrons (GER) If the substance is found in its neutral standard state, its oxidation state increases oxidation state decreases oxidation state will be zero. electrons are product electrons are reactant Na (s) = 0 or F 2(g) = 0 or C (graphite) = 0 Na (s) --> Na +(aq) + e - Mg 2+(aq) + 2e - --> Mg (s) If the substance is a molecular compound made of more than one element, the sum of the oxidation states must equal 0 C O 2 The less electronegative The more electronegative of the two receives the + -2 of the two receives a +4 charge necessary to charge equivalent to it's cancel out the negative normal ionic charge. charge

Slide 7 / 83 Slide 8 / 83 Oxidation States Oxidation States For ionic species, the sum of the oxidation states must equal Peroxides and hydrides the charge on the ion. S O 32- In a peroxide (H 2 O 2 or Na 2 O 2 ) O carries an oxidation state of -1. +4 -2 In a hydride (NaH or CaH 2 ), H carries an oxidation state of -1. For ionic compounds, first separate the compound into its ions, then determine charge on each element. Mg Cr 2 O 7 +2 -2 Cr 2 O 7 + 6 -2 Slide 9 / 83 Slide 9 (Answer) / 83 1 Oxidation/Reduction reactions study the transfer of 1 Oxidation/Reduction reactions study the transfer of ________ between atoms and molecules. ________ between atoms and molecules. A protons A protons Answer B neutrons B neutrons A C H+ ions C H+ ions D OH- ions D OH- ions E electrons E electrons [This object is a pull tab] Slide 10 / 83 Slide 10 (Answer) / 83 2 Which of the substances found in the reaction below 2 Which of the substances found in the reaction below would contain an element with an would contain an element with an oxidation number = 0? oxidation number = 0? 10Au (s) + 36H +(aq) + 6NO 3-(aq) --> 3N 2(g) + 18H 2 O (l) + 10Au 3+(aq) 10Au (s) + 36H +(aq) + 6NO 3-(aq) --> 3N 2(g) + 18H 2 O (l) + 10Au 3+(aq) Answer A Au A Au C B HNO 3 B HNO 3 C Au and N 2 C Au and N 2 D Au and H 2 O D Au and H 2 O E N 2 and Au 3+ E N 2 and Au 3+ [This object is a pull tab]

Slide 11 / 83 Slide 11 (Answer) / 83 3 In the substance glucose (C 6 H 12 O 6 ), the sum total of 3 In the substance glucose (C 6 H 12 O 6 ), the sum total of the oxidation states must equal _____. the oxidation states must equal _____. Answer A A 0 A 0 B +1 B +1 The sum total of the number of valence electrons The sum total of the number of valence electrons C C present in each element present in each element [This object is a pull tab] D +3 D +3 E 24 E 24 Slide 12 / 83 Slide 12 (Answer) / 83 4 In the compound IBr, which element would be the 4 In the compound IBr, which element would be the most electronegative and what would it's oxidation most electronegative and what would it's oxidation state be? state be? A I, -1 A I, -1 B Br, -1 B Br, -1 I I Br Br Answer C I, 0 C I, 0 B D Br, 0 D Br, 0 E Br, +1 E Br, +1 [This object is a pull tab] Slide 13 / 83 Slide 13 (Answer) / 83 5 The oxalate ion, C 2 O 42- , is one of the common 5 The oxalate ion, C 2 O 42- , is one of the common components of kidney stones! Which is the more components of kidney stones! Which is the more electronegative atom in the ion and what is it's electronegative atom in the ion and what is it's oxidation state? oxidation state? A C, +4 A C, +4 B C, -2 B C, -2 Answer D C C, -4 C C, -4 O, -2 O, -2 D D E O, -4 E O, -4 [This object is a pull tab]

Slide 14 / 83 Slide 14 (Answer) / 83 6 The polyatomic ion cyanide (CN-) is toxic and used 6 The polyatomic ion cyanide (CN-) is toxic and used in the mining of gold in America's desert southwest. in the mining of gold in America's desert southwest. Which of the following could be a correct set of Which of the following could be a correct set of oxidation states for C and N in the ion? oxidation states for C and N in the ion? Answer C A C = +4, N = -3 A C = +4, N = -3 B C = +4, N = 0 B C = +4, N = 0 C C = +2, N = -3 C C = +2, N = -3 D C = 0, N = +1 D C = 0, N = +1 [This object is a pull tab] E C = -3, N = +4 E C = -3, N = +4 Slide 15 / 83 Slide 15 (Answer) / 83 7 What is the oxidation state of O in the compound 7 What is the oxidation state of O in the compound N 2 O (laughing gas) and what would be the total N 2 O (laughing gas) and what would be the total negative charge from all the oxygens? negative charge from all the oxygens? A -2, -2 N A -2, -2 N N N O O B -1, 0 B -1, 0 Answer C -2, 0 C -2, 0 A D -2, -4 D -2, -4 -2, -4 -2, -4 E E [This object is a pull tab] Slide 16 / 83 Slide 16 (Answer) / 83 8 What would be the oxidation state of the fluorine 8 What would be the oxidation state of the fluorine atom in the compound OF 2 and what would be the atom in the compound OF 2 and what would be the total negative charge from the Flourines? total negative charge from the Flourines? A -1, -1 A -1, -1 B 0, -1 B 0, -1 Answer C C -1, -2 C -1, -2 -1, -3 -1, -3 D D E -1, 0 E -1, 0 [This object is a pull tab]

Slide 17 / 83 Slide 17 (Answer) / 83 Slide 18 / 83 Slide 18 (Answer) / 83 10 10 What is the oxidation number of each oxygen What is the oxidation number of each oxygen atom in the compound MnO 2 ? atom in the compound MnO 2 ? A -2 A -2 Answer B -1 B -1 A C 0 C 0 D +1 D +1 +2 +2 E E [This object is a pull tab] Slide 19 / 83 Slide 19 (Answer) / 83 11 What is the oxidation state of S in the S 2 O 32- ion? 11 What is the oxidation state of S in the S 2 O 32- ion? The S 2 O 32- ion can do great harm to metals like iron. The S 2 O 32- ion can do great harm to metals like iron. A -2 A -2 Answer B B +2 B +2 C -1 C -1 D +4 D +4 E 0 E 0 [This object is a pull tab]

Slide 20 / 83 Slide 20 (Answer) / 83 12 What is the oxidation state of each atom in 12 What is the oxidation state of each atom in CaC 2 O 4 ? CaC 2 O 4 ? A Ca = 0, C = +2, O = -2 A Ca = 0, C = +2, O = -2 B Ca = +2, C = +2, O = -2 B Ca = +2, C = +2, O = -2 Answer C Ca = +4, C = +4, O =-2 C Ca = +4, C = +4, O =-2 D Ca = +2, C = +3, O = -2 Ca = +2, C = +3, O = -2 D D Ca = +2, C = +4, O = -2 Ca = +2, C = +4, O = -2 E E [This object is a pull tab] Slide 21 / 83 Slide 21 (Answer) / 83 13 In 2004, Coca cola had to recall their Dasani brand 13 In 2004, Coca cola had to recall their Dasani brand water because of the presence of the bromate ion in the water because of the presence of the bromate ion in the drinking water. What would be the oxidation state of all drinking water. What would be the oxidation state of all atoms in CuBrO 3 ? atoms in CuBrO 3 ? A Cu = +2, Br = -1, O = -2 A Cu = +2, Br = -1, O = -2 Answer D B Cu = +1, Br = +3, O = -2 B Cu = +1, Br = +3, O = -2 C Cu = +2, Br = +4, O = -2 C Cu = +2, Br = +4, O = -2 Cu = +1, Br = +5, O =-2 Cu = +1, Br = +5, O =-2 D D [This object is a pull tab] Cu = 0, Br = +6, O =-2 Cu = 0, Br = +6, O =-2 E E Slide 22 / 83 Slide 22 (Answer) / 83 14 Chloroform, CHCl 3 , has wide uses. It is used as an 14 Chloroform, CHCl 3 , has wide uses. It is used as an anesthetic, a refrigerant, and in the making of teflon. anesthetic, a refrigerant, and in the making of teflon. What is the oxidation state of carbon in chloroform? What is the oxidation state of carbon in chloroform? A -2 A -2 B -1 B -1 Answer D C 0 C 0 D +2 D +2 E -3 E -3 [This object is a pull tab]