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1 TP Identify the correct statement about the redox reaction Zn 2 Cu Cu 2 Zn. 1. Zn 2 is the reducing agent because it gains electrons 2. Cu is the reducing agent because it gains electrons 3. Zn 2 is the reducing agent because it loses electrons 4. Cu is the reducing agent because it loses electrons 5. Zn 2 is the reducing agent because it is reduced 6. Cu is the reducing agent because it is reduced Lecture 21 CH101 A1 (MWF 9:05 am) Wednesday, October 25, 2017 For today To memorize: Table 6.13, p 194: Common acids and bases Balancing oxidation reduction equations Complexation as Lewis acid base reaction Begin ch7: Chemical reactions and energy flows First law of thermodynamics Next lecture: System vs. surroundings; Detecting heat; Predicting sign of heat; Detecting work; Amount of heat depends on whether there is work 1 Memorize: Table 6.13: Common acids and bases Oxidation reduction reactions are a competition for electrons Species that gives up e is oxidized It makes possible reduction and so is called the reducing agent 3 5 Copyright 2017 Dan Dill dan@bu.edu 1

2 Redox reactions are a competition for electrons 2 Ag Cu 2 Ag Cu 2 Oxidation half reaction? Oxidation reduction reactions are a competition for electrons Species that accepts e is reduced It makes possible oxidation and so is called the oxidizing agent 6 7 Redox reactions are a competition for electrons 2 Ag Cu 2 Ag Cu 2 Reduction half reaction? Getting balanced redox (full) reaction First, get the balanced half reactions 2 Ag aq Cu s 2 Ag s Cu 2 aq Then, combine the half reactions so that the electrons released in the oxidation are exactly consumed in the reduction 8 9 Copyright 2017 Dan Dill dan@bu.edu 2

3 TP Identify the correct statement about the redox reaction Zn 2 Cu Cu 2 Zn. 1. Zn 2 is the reducing agent because it gains electrons 2. Cu is the reducing agent because it gains electrons 3. Zn 2 is the reducing agent because it loses electrons 4. Cu is the reducing agent because it loses electrons 5. Zn 2 is the reducing agent because it is reduced 6. Cu is the reducing agent because it is reduced Lewis alternative definition of acids and bases Brønsted Lowry acid is the source of a proton HCl H 2 O H 3 O Cl Brønsted Lowry base is destination of proton NH 4 OH H 2 O NH Lewis alternative definition of acids and bases Lewis acid accepts a pair of electrons to form a covalent bond Lewis base has a pair of electrons to form a covalent bond Co 3 :NH 3 Co :NH 3 3 Result is acid base adduct Copyright 2017 Dan Dill dan@bu.edu 3

4 26 27 Be 2 aq 4 H 2 O l Be H 2 O 4 2 aq Cu 2 aq 4 NH 3 aq Cu NH aq Copyright 2017 Dan Dill dan@bu.edu 4

5 Complexes have characteristic colors TP In the reaction Cu :OH :Cl 2 :NH 3 Cu :NH 3 2 :Cl :OH 2 l the number of Lewis acids is Ch 7: Chemical Reactions and Energy Flows First law of thermodynamics Energy,, is exchanged between system and surroundings as heat,, and work,, Δ Positive values increase energy of system Δ heat flow into the system done on the system Copyright 2017 Dan Dill dan@bu.edu 5

6 TP In a certain chemical reaction, 10 kj of heat flow into the system and the system does 21 kj of work on the surroundings. This means ΔU = kj kj kj kj kj kj kj kj 38 First law of thermodynamics In a certain chemical reaction, 10 kj of heat flow into the system and the system does 21 kj of work on the surroundings. Sketch the energy diagram showing,, and Δ for this reaction. Indicate the initial and final energy by horizontal lines labeled and, respectively. 39 Copyright 2017 Dan Dill dan@bu.edu 6