Lecture 31 Objectives 30d continued Components of galvanic cell 31a Write net redox reactions a Describe the process used to identify a spontaneous redox reaction and write the net reaction Step 1 Look up the reactions in Reduction Table List them with most negative on top and most positive on bottom Step 2 The anode is always on the top most The cathode is always on the bottom most Step 3 E cell E cat E an Step 4 The bottom reaction can be left alone because reduction occurs at the cathode The top reaction must be reversed because oxidation occurs at the anode Step 5 Add the two rxns together in such a way that the electrons cancel out This is the net redox reaction Step 6 The number of electrons needed on each side to balance the redox reaction is the number of electrons transferred Step 7 Put the reactions with a picture of a battery Step 8 The salt bridge cations always migrate to the cat The salt bridge anions always migrate to the an Step 9 The cathode electrode usually grows The anode electrode usually shrinks 1 Construct a Galvanic cell using Ag1 Ag and Cr3 Cr Q31 1 What is the anode reaction A B C D Ag 1 1e Ag Ag Ag1 1eCr 3 3e Cr Cr Cr3 3e Ag1 aq 1e Ag s Cr3 aq 3e Cr s 0 80 V 0 74 V 2 Construct a Galvanic cell using Ag1 Ag and Cr3 Cr Q31 2 What is the cathode reaction A B C D Ag 1 1e Ag Ag Ag1 1eCr 3 3e Cr Cr Cr3 3e 3 Construct a Galvanic cell using Ag1 Ag and Cr3 Cr Q31 3 What is the net redox reaction A B C D Ag 1 Cr Ag Cr 3 Ag Cr 3 Ag 1 Cr 3Ag 1 Cr 3Ag Cr 3 3Ag 1 Cr 3 3Ag Cr 4 Construct a Galvanic cell using Ag1 Ag and 3 CrQ31 4 Cr Which compartment is the cathode How many electrons are transferred Which way to the electrons travel A B C D A 6 left A 3 left B 6 right B 3 right A B 5 Construct a Galvanic cell using Ag1 Ag and Cr3 Cr Q31 5 Which way do the anions in the salt bridge migrate Which solution becomes more concentrated in ions as the reaction progresses A B C D Toward A A Toward A B Toward B A Toward B B A B 6