Section 18 Electrochemistry

Chapter 18 electrochemistry l.jpg
1 / 93
0
0
1407 days ago, 521 views
PowerPoint PPT Presentation

Presentation Transcript

Slide 1

Science: A Molecular Approach , 1 st Ed. Nivaldo Tro Chapter 18 Electrochemistry Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA 2007, Prentice Hall

Slide 2

Redox Reaction at least one components change oxidation number all single removal, and ignition, some blend and deterioration dependably have both oxidation and diminishment split response into oxidation half-response and a lessening half-response otherwise known as electron exchange responses half-responses incorporate electrons oxidizing specialist is reactant particle that causes oxidation contains component decreased lessening operator is reactant particle that causes decrease contains the component oxidized Tro, Chemistry: A Molecular Approach

Slide 3

Oxidation & Reduction oxidation is the procedure that happens when oxidation number of a component expands component loses electrons compound includes oxygen compound loses hydrogen half-response has electrons as items lessening is the procedure that happens when oxidation number of a component diminishes component picks up electrons compound loses oxygen compound additions hydrogen half-responses have electrons as reactants Tro, Chemistry: A Molecular Approach

Slide 4

Rules for Assigning Oxidation States standards are all together of need free components have an oxidation state = 0 Na = 0 and Cl 2 = 0 in 2 Na(s) + Cl 2 (g) monatomic particles have an oxidation state equivalent to their charge Na = +1 and Cl = - 1 in NaCl (a) the total of the oxidation conditions of the considerable number of iotas in a compound is 0 Na = +1 and Cl = - 1 in NaCl, (+1) + (- 1) = 0 Tro, Chemistry: A Molecular Approach

Slide 5

Rules for Assigning Oxidation States (b) the total of the oxidation conditions of the considerable number of particles in a polyatomic particle measures up to the charge on the particle N = +5 and O = - 2 in NO 3 – , (+5) + 3(- 2) = - 1 (a) Group I metals have an oxidation condition of +1 in every one of their mixes Na = +1 in NaCl (b) Group II metals have an oxidation condition of +2 in every one of their mixes Mg = +2 in MgCl 2 Tro, Chemistry: A Molecular Approach

Slide 6

Rules for Assigning Oxidation States in their mixes, nonmetals have oxidation states as indicated by the table beneath nonmetals higher on the table take need Tro, Chemistry: A Molecular Approach

Slide 7

oxidation lessening Oxidation and Reduction oxidation happens when a particle's oxidation state increments amid a response lessening happens when a particle's oxidation state diminishes amid a response CH 4 + 2 O 2 → CO 2 + 2 H 2 O - 4 +1 0 +4 –2 +1 - 2 Tro, Chemistry: A Molecular Approach

Slide 8

Oxidation –Reduction oxidation and decrease must happen all the while if an iota loses electrons another molecule must take them the reactant that decreases a component in another reactant is known as the decreasing specialist the lessening specialist contains the component that is oxidized the reactant that oxidizes a component in another reactant is known as the oxidizing specialist the oxidizing specialist contains the component that is decreased 2 Na(s) + Cl 2 (g) → 2 Na + Cl – (s) Na is oxidized, Cl is decreased Na is the lessening operator, Cl 2 is the oxidizing specialist Tro, Chemistry: A Molecular Approach

Slide 9

Identify the Oxidizing and Reducing Agents in Each of the Following 3 H 2 S + 2 NO 3 – + 2 H + ® 3 S + 2 NO + 4 H 2 O MnO 2 + 4 HBr ® MnBr 2 + Br 2 + 2 H 2 O Tro, Chemistry: A Molecular Approach

Slide 10

oxidation diminishment oxidation diminishment Identify the Oxidizing and Reducing Agents in Each of the Following red ag bull ag 3 H 2 S + 2 NO 3 – + 2 H + ® 3 S + 2 NO + 4 H 2 O MnO 2 + 4 HBr ® MnBr 2 + Br 2 + 2 H 2 O +1 - 2 +5 - 2 +1 0 +2 - 2 +1 - 2 bull ag red ag +4 - 2 +1 - 1 +2 - 1 0 +1 - 2 Tro, Chemistry: A Molecular Approach

Slide 11

Common Oxidizing Agents

Slide 12

Common Reducing Agents

Slide 13

Balancing Redox Reactions allot oxidation numbers decide component oxidized and component diminished compose bull. & red. half-responses, including electrons bull. electrons on right, red. electrons on left of bolt adjust half-responses by mass first adjust components other than H and O include H 2 O where require O include H +1 where require H kill H + with OH - in base adjust half-responses by charge adjust charge by conforming electrons adjust electrons between half-responses include half-responses check Tro, Chemistry: A Molecular Approach

Slide 14

Ex 18.3 – Balance the condition: I  ( aq ) + MnO 4  ( aq )  I 2( aq ) + MnO 2( s ) in fundamental arrangement Tro, Chemistry: A Molecular Approach

Slide 15

Ex 18.3 – Balance the condition: I  ( aq ) + MnO 4  ( aq )  I 2( aq ) + MnO 2( s ) in essential arrangement Tro, Chemistry: A Molecular Approach

Slide 16

Ex 18.3 – Balance the condition: I  ( aq ) + MnO 4  ( aq )  I 2( aq ) + MnO 2( s ) in essential arrangement Tro, Chemistry: A Molecular Approach

Slide 17

Ex 18.3 – Balance the condition: I  ( aq ) + MnO 4  ( aq )  I 2( aq ) + MnO 2( s ) in essential arrangement Tro, Chemistry: A Molecular Approach

Slide 18

Practice - Balance the Equation ClO 3 - 1 + Cl - 1 ® Cl 2 (in corrosive) Tro, Chemistry: A Molecular Approach

Slide 19

Practice - Balance the Equation ClO 3 - 1 + Cl - 1 ® Cl 2 (in corrosive) +5 - 2 - 1 0 oxidation decrease ox: 2 Cl - 1 ® Cl 2 + 2 e - 1 } x 5 red: 2 ClO 3 - 1 + 10 e - 1 + 12 H + ® Cl 2 + 6 H 2 O} x 1 tot 10 Cl - 1 + 2 ClO 3 - 1 + 12 H + ® 6 Cl 2 + 6 H 2 O 1 ClO 3 - 1 + 5 Cl - 1 + 6 H +1 ® 3 Cl 2 + 3 H 2 O Tro, Chemistry: A Molecular Approach

Slide 20

Electrical Current when we discuss the ebb and flow of a fluid in a stream, we are talking about the measure of water that goes by in a given timeframe when we examine electric ebb and flow, we are examining the measure of electric charge that passes a point in a given timeframe whether as electrons coursing through a wire or particles moving through an answer Tro, Chemistry: A Molecular Approach

Slide 21

Redox Reactions & Current redox responses include the exchange of electrons starting with one substance then onto the next hence, redox responses can possibly create an electric ebb and flow so as to utilize that ebb and flow, we have to isolate the place where oxidation is happening from the place that lessening is happening Tro, Chemistry: A Molecular Approach

Slide 22

Electric Current Flowing Directly Between Atoms Tro, Chemistry: A Molecular Approach

Slide 23

Electric Current Flowing Indirectly Between Atoms Tro, Chemistry: A Molecular Approach

Slide 24

Electrochemical Cells electrochemistry is the investigation of redox responses that deliver or require an electric ebb and flow the transformation between compound vitality and electrical vitality is done in an electrochemical cell unconstrained redox responses happen in a voltaic cell otherwise known as galvanic cells nonspontaneous redox responses can be made to happen in an electrolytic cell by the expansion of electrical vitality Tro, Chemistry: A Molecular Approach

Slide 25

Electrochemical Cells oxidation and diminishment responses kept separate half-cells electron move through a wire alongside particle move through an answer constitutes an electric circuit requires a conductive strong (metal or graphite) terminal to permit the exchange of electrons through outside circuit particle trade between the two parts of the framework electrolyte Tro, Chemistry: A Molecular Approach

Slide 26

Electrodes Anode terminal where oxidation happens anions pulled in to it associated with positive end of battery in electrolytic cell sheds pounds in electrolytic cell cathode where lessening happens cations pulled in to it associated with negative end of battery in electrolytic cell puts on weight in electrolytic cell cathode where plating happens in electroplating Tro, Chemistry: A Molecular Approach

Slide 27

Voltaic Cell the salt extension is required to finish the circuit and keep up charge adjust Tro, Chemistry: A Molecular Approach

Slide 28

Current and Voltage the quantity of electrons that move through the framework every second is the momentum unit = Ampere 1 An of ebb and flow = 1 Coulomb of charge streaming by every second 1 A = 6.242 x 10 18 electrons/second Electrode surface range manages the quantity of electrons that can stream the distinction in potential vitality between the reactants and items is the potential contrast unit = Volt 1 V of compel = 1 J of vitality/Coulomb of charge the voltage expected to drive electrons through the outer circuit measure of constrain pushing the electrons through the wire is known as the electromotive constrain, emf Tro, Chemistry: A Molecular Approach

Slide 29

Cell Potential the distinction in potential vitality between the anode the cathode in a voltaic cell is known as the phone potential the phone potential relies on upon the relative simplicity with which the oxidizing specialist is diminished at the cathode and the decreasing operator is oxidized at the anode the phone potential under standard conditions is known as the standard emf, E° cell 25°C, 1 atm for gasses, 1 M grouping of arrangement whole of the cell possibilities for the half-responses Tro, Chemistry: A Molecular Approach

Slide 30

Cell Notation shorthand depiction of Voltaic cell cathode | electrolyte || electrolyte | terminal oxidation half-cell on left, decrease half-cell on the right single | = stage obstruction if various electrolytes in same stage, a comma is utilized instead of | frequently utilize a latent cathode twofold line || = salt scaffold Tro, Chemistry: A Molecular Approach

Slide 31

Fe(s) | Fe 2+ ( aq ) || MnO 4  ( aq ), Mn 2+ ( aq ), H + ( aq ) | Pt( s ) Tro, Chemistry: A Molecular Approach

Slide 32

Standard Reduction Potential a half-response with a solid inclination to happen has a vast + half-cell potential when two half-cells are associated, the electrons will stream so that the half-response with the more grounded propensity will happen

SPONSORS