electrode potentia

Question 1

define half cell

Answer 1

A strip of metal dipped into a solution of its own ions can be called an ELECTRODE

Question 2

Why is KNO3 a suitable solution for a salt bridge

Answer 2

KNO3 is unreactive with the elecrodes AND the ions are free to mov

Question 3

where is the most reactive metal in a circuit

Answer 3

left

Question 4

Why might the current produced by a cell fall to zero after some time

Answer 4

all reactants used up

Question 5

What will happen to a cell once the reactants are used up?

Answer 5

stops working OR starts to leak

Question 6

where does oxidation always occur

Answer 6

left negative electrode

Question 7

when at Pt electrodes used

Answer 7

when there is no solid metal in the reaction, such as when there are metal ions of two different charges in the same solution

Question 8

Why is platinum a suitable electrode

Answer 8

unreactive and conducts electricity

Question 9

conditions for standard electrode

Answer 9

100kPa, 1moldm-3, Pt electrode, 298K

Question 10

The voltage of the Standard Hydrogen Half Cell is defined as

Answer 10

zero

Question 11

vertical solid lines indicate in a circuit a

Answer 11

phase boundary

Question 12

Which is the strongest oxidising agent(SO

Answer 12

strongest oxidising agent on the left will have most positive standard electrode potential

Question 13

Which is the weakest reducing agent (WR)

Answer 13

weakest reducing agent on the right will have most positive standard electrode potential

Question 14

if an ion is more positive then

Answer 14

it will react

Question 15

how do you work out EMF

Answer 15

more positive - least positive

Question 16

Give an environmental advantage of using rechargeable cells

Answer 16

Metals are reused

Question 17

Give an environmental disadvantage of using rechargeable cells

Answer 17

Mains electricity is used to recharge, which may come from combusting fossil fuels, which releases CO2(

Question 18

Q: The cell made of the systems Mg/Mg2+ and Fe2+/Fe under standard conditions has an e.m.f. of 1.93 V.

Deduce how the e.m.f. of the cell Mg/Mg2+ and Fe2+/Fe changes when the concentration of Mg2+ is decreased. Explain your answer. (3 marks)

Use the data below;

E/ V

Mg2+(aq) + 2e– Mg(s) –2.37

Fe2+(aq) + 2e– Fe(s) –0.44

Answer 18

When Mg2+ is decreased, the equilibria shifts left.

So the Evalue at the Mg2+ electrode becomes more negative, as more electrons are made

e.m.f. = more positive – least positive = -0.44 – (-2.37) = 1.93 V

So after the Mg2+ is increased the -2.37 could become around -2.40,

e.m.f. = -0.44 – (-2.40) = 1.96 V

Question 19

Advantages of using fuel cells for energy instead of fossil fuels.

Answer 19

• Major advantage; Greater efficiency than burning hydrogen in a combustion engine
• Less-polluting as water is the only product

Question 20

Disadvantages of using fuel cells for energy instead of fossil fuels.

Answer 20

• H2 is difficult to store
• Fossil fuels are combusted to produce the hydrogen, which releases carbon dioxide

Question 21

Advantages of fuel cells compared to other types of cell

Answer 21

Voltage is constant, as fuel and oxygen is supplied constantly so concentrations of reactants remain constant

Question 22

State the meaning of the term electrochemical series

Answer 22

(List of) electrode potentials/ in (numerical) order