Slide 1 of 26 Chemistry 20.2. © Copyright Pearson Prentice Hall Slide 2 of 26 Oxidation Numbers...
-
Upload
darrell-manning -
Category
Documents
-
view
218 -
download
1
Transcript of Slide 1 of 26 Chemistry 20.2. © Copyright Pearson Prentice Hall Slide 2 of 26 Oxidation Numbers...
Slide 1 of 26
Chemistry 20.2
© Copyright Pearson Prentice Hall
Slide 2 of 26
Oxidation Numbers
When aluminum or magnesium powder in fireworks are heated to high temperatures in the explosion, they burn with an intense white light. As elements burn, their oxidation numbers change. You will learn about how oxidation and reduction are defined in terms of a change in oxidation number.
20.2
© Copyright Pearson Prentice Hall
Oxidation Numbers >
Slide 3 of 26
Assigning Oxidation Numbers
Assigning Oxidation Numbers
What is the general rule for assigning oxidation numbers?
20.2
Slide 4 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Assigning Oxidation Numbers
An oxidation number is a positive or negative number assigned to an atom to indicate its degree of oxidation or reduction.
20.2
© Copyright Pearson Prentice Hall
Slide 5 of 26
Oxidation Numbers > Assigning Oxidation Numbers
As a general rule, a bonded atom’s oxidation number is the charge that it would have if the electrons in the bond were assigned to the atom of the more electronegative element.
20.2
Slide 6 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Assigning Oxidation Numbers
The oxidation number of any element in the free or uncombined state is zero.
20.2
Slide 7 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Assigning Oxidation Numbers20.2
Slide 8 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Assigning Oxidation Numbers
Oxidation numbers are often written above the chemical symbols in a formula.
20.2
Slide 9 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Assigning Oxidation Numbers
K2CrO4
Cr oxidation number = +6
Cr2O3
Cr oxidation number = +3
20.2
© Copyright Pearson Prentice Hall
Slide 10 of 26
© Copyright Pearson Prentice Hall
Slide 11 of 26
© Copyright Pearson Prentice Hall
Slide 12 of 26
© Copyright Pearson Prentice Hall
Slide 13 of 26
© Copyright Pearson Prentice Hall
Slide 14 of 26
Practice Problems for Conceptual Problem 20.2
Problem Solving 20.9 Solve Problem 9 with the help of an interactive guided tutorial.
© Copyright Pearson Prentice Hall
Oxidation Numbers >
Slide 15 of 26
Oxidation-Number Changes in Chemical Reactions
Oxidation-Number Changes in Chemical Reactions
How are oxidation and reduction defined in terms of a change in oxidation number?
20.2
© Copyright Pearson Prentice Hall
Slide 16 of 26
Oxidation Numbers > Oxidation-Number Changes in Chemical Reactions
An increase in the oxidation number of an atom or ion indicates oxidation. A decrease in the oxidation number of an atom or ion indicates reduction.
20.2
Slide 17 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Oxidation-Number Changes in Chemical Reactions
20.2
Slide 18 of 26
© Copyright Pearson Prentice Hall
Oxidation Numbers > Oxidation-Number Changes in Chemical Reactions
When an iron nail is placed in a copper(II) sulfate solution, the iron reduces Cu2+ ions in solution and is simultaneously oxidized to Fe2+ The iron becomes coated with metallic copper.
20.2
© Copyright Pearson Prentice Hall
Slide 19 of 26
© Copyright Pearson Prentice Hall
Slide 20 of 26
© Copyright Pearson Prentice Hall
Slide 21 of 26
© Copyright Pearson Prentice Hall
Slide 22 of 26
Practice Problems for Conceptual Problem 20.3
Problem Solving 20.11 Solve Problem 11 with the help of an interactive guided tutorial.
© Copyright Pearson Prentice Hall
Slide 23 of 26
Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
20.2 Section Quiz.
20.2.
© Copyright Pearson Prentice Hall
Slide 24 of 26
20.2 Section Quiz.
1. Which of the following oxidation numbers is INCORRECT?
a. ClO3– ; Cl +5, O –2
b. SO32– ; S +4, O –2
c. H2O2; H +1, O –1
d. Ca(ClO)2; Ca +2, Cl +2, O –2
© Copyright Pearson Prentice Hall
Slide 25 of 26
20.2 Section Quiz.
2. What is the oxidation number of Co in CoCl63–?
a. –3
b. –6
c. +9
d. +3
© Copyright Pearson Prentice Hall
Slide 26 of 26
20.2 Section Quiz.
3. In the reaction PbO2(aq) + 4HBr(aq) PbBr2(aq) + Br2(l) + 2H2O(l) which element has the greatest change in oxidation number?
a. hydrogen
b. oxygen
c. bromine
d. lead
END OF SHOW