Oxidation Numbers and Redox Reactions

Slides:



Advertisements
Similar presentations
Oxidation and Reduction (Redox) Lance S. Lund April 19, 2011.
Advertisements

Oxidation and Reduction Chem 1061 – Tro, Chapter 4 Lance S. Lund.
Oxidation-reduction reactions
Copyright Sautter REVIEW OF ELECTROCHEMISTRY All electrochemical reactions involve oxidation and reduction. Oxidation means the loss of electrons.
7.2 Oxidation Numbers April 24, Oxidation Numbers  In order to indicate the general distribution of electrons among the bonded atoms in a molecular.
Redox Reactions. What is redox? Redox reactions involve a transfer of electrons. Oxidation – involves losing electrons (increase in oxidation number)
Redox Reactions What is oxidation? What is reduction?
Oxidation Reduction Reactions. Oxidation Reduction Reactions… are chemical changes that occur when electrons are transferred between reactants.
Objectives Assign oxidation numbers to reactant and product species. Define oxidation and reduction. Explain what an oxidation-reduction reaction (redox.
REDOX Reactions Oxidation – Reduction.
Redox Reactions: Oxidation and Reduction. I. ELECTRON TRANSFER AND REDOX REACTIONS.
UNIT 6: ELECTROCHEMISTRY. REDOX REACTIONS Redox is short for ‘oxidation and reduction’ Oxidation refers to substances that combine with oxygen Iron rusting,
Electrochemistry Reduction-Oxidation. Oxidation Historically means “to combine with oxygen” Reactions of substances with oxygen, ie Combustion, Rusting.
REDOX Oxidation and Reduction Chapters 20 and 21.
Oxidation Numbers & Redox Reactions How to Make Balancing Redox Reactions a Relatively Painless Process.
1 Oxidation- Reduction Chapter 16 Tro, 2 nd ed. 1.1.
Oxidation Number. What is an Oxidation Number? Oxidation-reduction reactions (redox reactions) are reactions in which electrons are lost by an atom or.
Chapter 19 Oxidation - Reduction Reactions 19.1 Oxidation and Reduction.
1 Chapter 19 Oxidation and Reduction (basic facts) A substance is oxidized if it loses electrons (becomes more positive) A substance is reduced if it gains.
Chapter 16 Oxidation-Reduction Reactions. Objectives 16.1 Analyze the characteristics of an oxidation reduction reaction 16.1 Distinguish between oxidation.
Redox Reactions. Redox is the abbreviated way to write reduction- oxidation reaction. Redox is the abbreviated way to write reduction- oxidation reaction.
Redox and Electrochemistry. Redox Reactions Reduction – Oxidation reactions Involve the transfer of electrons from one substance to another The oxidation.
Oxidation-Reduction Reactions Redox. Iron is oxidized when it rusts.
Daniel L. Reger Scott R. Goode David W. Ball Lecture 03B (Chapter 18, sections 18.1, 18.2) Balancing Redox Reactions.
Oxidation Numbers and Redox Reactions Section 7.2.
Oxidation, Reduction and Electrochemistry
The Finish Line is in site… Electrochemistry. Oxidation Numbers OBJECTIVES Determine the oxidation number of an atom of any element in a pure substance.
Chemical Formulas and Chemical Compounds Oxidation Numbers.
Section 7-2. Oxidation Numbers (aka Oxidation States) Are used to indicate and assign the general distribution of electrons among the bonded atoms in.
Copper oxidizes in air to form the green patina.
REDOX REACTIONS. Oxidation-Reduction reactions A reaction in which electrons are transferred from one atom to another Chemists often refer to oxidation-reactions.
Oxidation-Reduction Reactions “Redox” LEO SAYS GER.
Chapter 21- Electrochemistry Reduction-Oxidation or REDOX chemistry.
Aim: How do chemists assign oxidation numbers? An oxidation-reduction (redox) reaction involves the transfer of electrons (e-). Reduction is the gain of.
The Finish Line is in site…
Oxidation numbers.
Redox Reactions.
Identifying Redox Reactions
Oxidation-Reduction Topic 9 Review Book.
Oxidation-Reduction Reactions
Chapter 19 Oxidation and Reduction (basic facts)
Oxidation & Reduction Reactions
Chemistry 200 Fundamental G Oxidation & Reduction.
Oxidation-Reduction Reactions
Redox processes Topic 9 SL Chemistry.
Oxidation & Reduction Reactions Redox
Chapter 7 Oxidation Numbers
Oxidation and Reduction Reactions
REDOX INTRODUCTION.
Oxidation-Reduction.
Oxidation Reduction Chemisty: Redox Chemistry
Redox Reactions.
Electron Transfer and Redox Reactions
CHAPTER 20 “Oxidation-Reduction Reactions” LEO SAYS GER.
Chapter 19.1 oxidation number or oxidation state –
Also called Reduction-Oxidation Reactions
Oxidation-Reduction Topic 9 Review Book.
Oxidation & Reduction Reactions Redox
Unit 6 – Redox Reactions and Electrochemistry
Chapter 5 – Analysing Oxidants & Reductants
Oxidation-Reduction.
Chemical Formulas & Mass
Unit 11: Classification of Chemical Reactions
Oxidation Reduction Reactions
Redox Reactions Reduction Oxidation.
Unit 11: Classification of Chemical Reactions
Oxidation & Reduction Reactions Redox
Oxidation-Reduction Reactions
Chapter 7 – Chemical Formulas and Chemical Compounds
Unit 6: Electrochemistry
Presentation transcript:

Oxidation Numbers and Redox Reactions Section 7.2

Oxidation Numbers Oxidation number: the number of electrons that must be added to or removed from an atom in a combined state to convert the atom into the elemental form AKA oxidation state Do not have an exact physical meaning

Usage Useful for naming compounds, writing formulas, and balancing chemical equations There are specific rules for assigning oxidation numbers to a species Shared electrons are assumed to belong to the more electronegative atom in each bond

Rules Atoms in a pure element have an oxidation number of 0 F has an oxidation number of -1 O has an oxidation number of -2, except in peroxides (-1) or bonded with F (+2) H is +1 when in a compound where the other element is more electronegative than it is

Rules Continued H is -1 when it is bonded with metals The more-electronegative element in a binary molecular compound is assigned the number equal to the negative charge it would have as an anion, the other gets the positive charge it would get as a cation

Rules Continued The algebraic sum of the oxidation numbers of all atoms in a neutral compound is 0 The algebraic sum of the oxidation numbers of all atoms in a polyatomic ion is equal to the charge of the ion A monoatomic ion has an oxidation number equal to its charge

Practice Assign oxidation numbers to each atom: UF6 We know F has an oxidation number of -1, so the oxidation number for F6 is -6 Since the compound is neutral, the U must be +6 See the board for how to write this On the board show the individual numbers above each atom with the totals under each atom

Practice Assign oxidation numbers to each atom: H2SO4 H is bonded with more electronegative atoms, so it is +1 for each (total +2) O is -2 for each for a total of -8 S must be +6 to balance the neutral formula

Practice Assign oxidation numbers to each atom: ClO3- O is -2 for a total of -6 The charge on the ion is -1, so Cl must be +5 Practice problems on page 234 in the book at school.

Redox Reaction Reduction and oxidation occurs This is a reaction in which electrons are transferred from one atom to another Oxidation: loss of electrons Also the increase in oxidation number Reduction: gain of electrons Also the decrease in oxidation number LEO goes GER or OILRIG

Example of Redox Reaction Zn(s) + I2(aq) → Zn2+(aq) + 2 I-(aq) Half reactions are used to show redox Zn(s) → Zn2+(aq) + 2e- (oxidized) I2 (aq) + 2e- → 2 I-(aq) (reduced)

Oxidation Numbers in Redox Reactions 2KBr(aq) + Cl2(aq)  2KCl(aq) + Br2(aq) Assign oxidation numbers to all elements in the balanced equation K in KBr = +1, K in KCl = +1 (no change) Br in KBr = -1, Br in Br2 = 0 (increase) Cl in Cl2 = 0, Cl in KCl = -1 (decrease) Bromine is oxidized, chlorine is reduced

Reducing and Oxidizing Agents The species that is reduced is called the oxidizing agent The species that is oxidized is called the reducing agent. 2Zn + O2  2ZnO Zn in 2Zn = 0, Zn in ZnO = +2, Zn is oxidized and is the reducing agent

Continued O in O2 = 0, O in ZnO = -2, O is reduced and is the oxidizing agent Practice: identified which species is reduced, oxidized, the oxidizing agent, and the reducing agent N2(g) + 3H2(g)  2NH3(g) N is reduced, oxidizing agent, H is oxidized, reducing agent

Disproportionation Disproportionation: a process by which a substance acts as both the reducing agent and the oxidizing agent 2 Cu+(aq) → Cu2+(aq) + Cu(s) +1 +2 0