Ch. 5 Electrochemical Cells

Question 1

What are the two types of electrochemical cell

Answer 1

galvanic and electrolytic

Question 2

What are galvanic cells

Answer 2

Chemical potential energy into electrical energy

Question 3

What three parts are of a reference cell

Answer 3

hydrogen cell test cell and connecntion

Question 4

what does a salt bridge do

Answer 4

completes circuit
♣ Allows movement of ions so solutions remain natural and balance charge
♣ Anions flow to anode, cation flow to cathode
♣ No excess cations/anions at anode/cathode

Question 5

what are salt bridges made of and why

Answer 5

o paper filter soaked in electrolyte (e.g. KNO3) since it will not react with test or reference cells

Question 6

what electrodes does oxidation and reduction occur

Answer 6

RED CAT

Question 7

Is galvanic spontaneous

Answer 7

yes

Question 8

what charge is the overall voltage of galvanic cells

Answer 8

positive

Question 9

what happens if salt bridge form precipitate

Answer 9

(if precipitates= circuit broken as charge or electrons not free to move)

Question 10

what occurs at an anode

Answer 10

♣ Where oxidation occurs (loses electrons to form ion)
♣ Solid mass decrease
♣ Forms excess ions at anode
♣ Lost electrons flow from anode > cathode

Question 11

what occurs at a cathode

Answer 11

♣ Where reduction occurs (gains electrons to form solid)
♣ Electron combine with Cu ions in solution > solid copper
♣ Mass of solid cathode increases
♣ Forms excess sulphate ions at cathode

Question 12

Steps to write had equations using standard electrode potentials

Answer 12

1. Identify relevant equations and write, include Eo
2. Reverse one reaction
   o As spontaneous, overall charge= positive when voltages added together
   o Highest negative voltage is reversed so charge= positive
   o Reverse sign on voltage as well
   o The one that’s reversed= Oxidized (anode)
3. Balance electrons by multiplication (do not multiply Eo
4. Cancel electrons and add Eo together

Question 13

whats a fuel cell

Answer 13

electrochemical device that converts chemical energy directly into electrical energy

Question 14

difference between fuel cel and galvanic

Answer 14

o Fuel and air constantly fed into cell, electrons don’t need to be replaced

Question 15

what do nanoparticles used for in fuel cells

Answer 15

increase SA

Question 16

Why are electrolytic cells not spontaneous

Answer 16

requires energy to be put into them

Question 17

what is the overall charge for electrolytic cell

Answer 17

negative

Question 18

what three factors determine main reaction at anode and cathode

Answer 18

• Nature of electrolyte
• Concentration of electrolyte
• Nature of electrode

Question 19

what is the nature condition for electrolytic cells

Answer 19

– Need to determine which two reactions occur at each anode
o Split the solution into its two ions and assign to electrode
o Split water: O2 produced (oxidation), H2 (reduction)
- The reaction more likely to occur is the one that requires least input of energy (least negative)

Question 20

what is the concentration condition for electrolytic cells

Answer 20

• If Eo similar, concentrations considered
• In a more concentrated solution= more ions in same volume of solution
  o // likelihood that (in an anode) = will be oxidised

Question 21

what is the electrode nature condition for electrolytic cells

Answer 21

• If electrode inert, do not need to be considered
• But if more reactive electrode used, need to be considered in reactions at electrodes
• Preferred reaction= least negative
• Anode reaction considered

Question 22

when electroplating occurs, what is the cathode anode and electrolyte

Answer 22

o Cathode: Metallic object that is to be plated
o Electrolyte: Solution containing the metal to be plated onto the objection
o Anode: Either inert electrode, or metal to be plated (dependant on reactivity of metal)