EMF

Question 1

what is electrode potential a measure of?

Answer 1

oxidising ability

Question 2

what does a high and positive electrode potential mean?

Answer 2

very good oxidising agent

Question 3

what is the emf of a standard hydrogen electrode?

Answer 3

0

Question 4

why is the emf of the she 0?

Answer 4

acts as a baseline - used as a comparison

Question 5

how should the standard hydrogen electrode and the other half cell be connected?

Answer 5

with a high resistance voltmeter and a salt bridge

Question 6

how can you make a salt bridge?

Answer 6

soak filter paper in potassium chloride/nitrate

fill a u tube with KCl in agar jelly

Question 7

what is the purpose of a salt bridge?

Answer 7

completes the circuit

balances the charges

Question 8

why do you stopper the end of a salt bridge with cotton wool?

Answer 8

to stop too much mixing of salt bridge solution with the contents of the two beakers

Question 9

describe how the standard hydrogen electrode is set up

Answer 9

solution of H+ ions
platinum electrode (platinum foil over porous platinum)
H2 gas

Question 10

what standard conditions are all half cells under?

Answer 10

all solutions are 1M
gases at 100kPa
298K temp

Question 11

why do half cells need to be under standard conditions?

Answer 11

because the equilibrium shifts with a change in conditions

Question 12

why is a high resistance voltmeter needed when connecting two half cells?

Answer 12

to avoid the flow of current because this will cause a drop in the voltage

Question 13

define standard electrode potential

Answer 13

the electrode potential of a standard electrode with ion conc of 1M at 298K connected to a standard H electrode using a high resistance voltmeter and salt bridge

Question 14

which side does the oxidation half cell go on?

Answer 14

the left

Question 15

which side does the reduction electrode go on?

Answer 15

the right

Question 16

what is the equation to find the EMF of a whole cell?

Answer 16

E(rhs)-E(lhs)

Question 17

explain how electrode potentials can show the feasability of a cell?

Answer 17

the more positive a cell’s emf, the more feasible the reaction

Question 18

which side is the SHE always on?

Answer 18

the left

Question 19

give a commercial use of cells

Answer 19

commercial source of electrical energy

Question 20

what are primary cells?

Answer 20

single use/disposable cells

Question 21

what are secondary cells?

Answer 21

rechargeable cells

Question 22

what’s an example of a non-rechargeable cell?

Answer 22

Zn and MnO2

Question 23

advantages of non-rechargeable cells

Answer 23

low cost

non-toxic material

Question 24

disadvantages of non-rechargeable cells

Answer 24

can leak
cannot be recycled
unstable

Question 25

give examples of rechargeable cells

Answer 25

nickel cadmium lead-acid lithium ion

Question 26

give some uses of lithium ion cells

Answer 26

provide electrical energy for tablets, laptops and phones

Question 27

what is the purpose of graphite powder in a lithium fuel cell?

Answer 27

acts as a support medium

Question 28

why can water not be used in a lithium fuel cell?

Answer 28

reacts with the lithium

Question 29

give the equation of the oxidation reaction in a lithium ion cell

Answer 29

Li ----> Li+ + e-

Question 30

give the equation of the reduction reaction in a lithium ion cel

Answer 30

e- + Li+ + CoO2 ---> Li+[CoO2]-

Question 31

give the cell notation for a lithium ion cell

Answer 31

Li(s)/Li+(aq) // Li+, CoO2/ Li+[CoO2]-

Question 32

advantages of rechargeable cells?

Answer 32

reusable prevents waste slows depletion of metals and other reagents less energy used to extract metals

Question 33

what is a fuel cell?

Answer 33

a cell which converts chemical energy from a redox reaction into electrical energy (generate an electric current)

Question 34

what are the main types of fuel cell?

Answer 34

hydrogen or ethanol

Question 35

give the oxidation reaction in an acidic hydrogen fuel cell

Answer 35

H2(g) ----> 2H+(aq) + 2e-

Question 36

give the reduction reaction in the acidic hydrogen fuel cell?

Answer 36

O2(g) + 4H+ + 4e- -----> 2H2O (l)

Question 37

give the oxidation reaction in an alkaline hydrogen fuel cell

Answer 37

H2 + 2OH- ----> 2H2O

Question 38

give the reduction reaction in an alkaline hydrogen fuel cell

Answer 38

O2 (g) + 2H2O + 4e- ----> 4OH-

Question 39

what are the advantages of fuel cells?

Answer 39

no need to recharge them run for as long as you supply them with fuel steady output of voltage doesn't generate CO2 - only product is water

Question 40

what is the advantage of using fuel cells in cars?

Answer 40

uses more available energy for kinetic energy so less energy is wasted as heat

Question 41

what are the disadvantages of fuel cells?

Answer 41

not carbon neutral bc CO2 released when the methane and steam react to form hydrogen expensive difficult to store flammable