Chapter 8- Electrochemistry

Question 1

How do you balance redox equations in acidic solutions?

Answer 1

Balance like normal by splitting in half then add H2O to balance O and add H+ to the other side to balance the H’s

Question 2

How do you balance redox reactions in basic solutions?

Answer 2

After adding H20 and H+ to balance the reaction add equal amount of OH- to the H+ side and make water and cancel it with the H2O on the other side

Question 3

What is a voltaic or galvanic cell compared to an electrolytic cell?

Answer 3

Voltaic (galvanic)- electrochemical cell that produces electrical current from a spontaneous chemical reaction
Electrolytic cell- consumes electrical current to drive a nonspontaneous chemical reaction

Question 4

Study the voltaic cell structure on page 428

Answer 4

Aight

Question 5

What is electrical current driven by?

Answer 5

Potential difference- measure of the difference in potential energy per unit charge

Question 6

What is the cell potential or Ecell?

What is the standard cel potential (E•cell)?

Answer 6

The potential difference between the two electrodes, a measure of the overall tendency of the redox reaction to occur spontaneously

Standard cell potential is the potential at 1 atm, 1M and 1 mol, 25 celcius)

Question 7

Where does oxidation and reduction occur in an electrochemical cell

Answer 7

Oxidation- anode
Reduction- cathode

An Ox
Red Cat

Question 8

What is electrochemical cell notation?

Answer 8

Anode|Anodic solution(conc)||Cathodic solution(conc)|Cathode

Zn|Zn2+||Cu2+|Cu

Oxidation on left and reduction on right

Do not separate by single line if they are the same phase (use comma if two elements on same side of two lines are the same)

Question 9

What is the equation for the standard electrode potential (E*cell)?

Answer 9

Ecell=Ecathode-E*anode

Question 10

What is the standard electrode potential of hydrogen?

Answer 10

0.00 V

Question 11

What is the sign of E*cell for spontaneous and non spontaneous reactions?

Answer 11

Spontaneous- E*cell is positive

Nonspontaneous- E*cell is negative

Question 12

What does the mode negative and most positive E* half reactions do in a reaction?

Answer 12

Most negative E* half reaction- loses electrons and therefore undergoes oxidation
More positive E* half reaction- gains electrons and therefore undergoes reduction

Question 13

How do most acids dissolve metals?

Answer 13

By the reduction of H+ ions to hydrogen gas and the corresponding oxidation of the metal to its ion

Question 14

How can you look at the chart to determine which metals dissolve in acids?

Answer 14

Metals whose reduction half reactions lie below the reduction of H+ to H2 dissolve in acids while metals above do not

It needs to be a spontaneous process so metals must be less than H+

Exception for nitric acid

Question 15

What are the values for ΔG, Ecell, and K for a reaction that is spontaneous?
Non spontaneous?

Answer 15

Spontaneous
ΔG* is negative <0
E*cell is positive >0
K>1

Non-spontaneous
ΔG* is positive >0
E*cell is negative <0
K<1

Question 16

What is the equation relating ΔG* to E*cell using n and F?

Answer 16

ΔG= -nFEcell

n= number of electrons in half reactions
F= faradyas constant

Question 17

What is he equation relating E*cell to K using n?

Answer 17

E*cell=0.0592V/n (logK)

Comes from ΔG*=-RTlnK

Question 18

How to we find Ecell for reaction not in standard states?

Answer 18

Ecell=E*cell - 0.0592V/n (logQ)

Question 19

What is Ecell when a redox reaction within a voltaic cell occurs under standard conditions?
What about when a redox reaction reaches equilibrium?

Answer 19

Standard conditions- Ecell=E*cell

Equilibrium- Ecell= 0

Question 20

What is the equality equation between Ecell and E*cell for a redox reaction within a voltaic cell where Q<1?
How about in a electrochemical cell where Q>1?

Answer 20

Voltaic Q<1- Ecell>E*cell

Electrochemical Q>1- Ecell