137A- ions and electrochem

Question 1

define voltage

Answer 1

energy per unit charge V=IR

Question 2

What are other units for 1V

Answer 2

1J C-1

Question 3

Equation for work

Answer 3

W= QΔV

Question 4

define current

Answer 4

rate of flow of charge of electrons or ions

Question 5

other units for current A

Answer 5

1Cs-1

Question 6

charge on an electron or proton

Answer 6

+/-1.6 × 10-19 C

Question 7

Question 8

What is a redox reaction

Answer 8

about transfer of electrons between chemical species

Question 9

What are the half equations for zinc and copper

Answer 9

Question 10

What can a salt bridge be made of and what is its purpose

Answer 10

allow movement of ions / SO4 2-, KCl, AgNO3

Question 11

What oxidation/reduction at the anode/cathode

Answer 11

anode- electrode where oxidation happens
cathode-electrode where reduction happens

Question 12

What is the difference between an Electrolytic Cell Apparatus and Galvanic / Voltaic Cell

Answer 12

Electrolytic- consumes electricity
Galvanic / Voltaic Cell- produces electricity

Question 13

Draw hydrogen half cell

Answer 13

Question 14

Write out the cell diagram equation

Answer 14

Question 15

Write out the cell diagram equation

Answer 15

Question 16

Write out the cell diagram equation

Answer 16

Question 17

Answer 17

W= QV 2 x 5 = +10V

Question 18

Answer 18

-2 x (1.6x10^-19) x (6.022 x 10^23) x 0.7V

Question 19

Draw the cell diagram for

Answer 19

oxidation at anode and reduction at cathode.
Electrons flow from negative to positive so the anode must be on the left

Question 20

Answer 20

Question 21

A more reactive metal is more likely to be the cathode/anode

Answer 21

anode. loose e- easier and are more easily oxidised

Question 22

If the E value is larger, will the reaction be at the anode or cathode

Answer 22

higher (more positive) E= cathode reduction
lower E= anode oxidation

Question 23

What is the equation for E cell

Answer 23

cathode- anode/ most positive- most negative

Question 24

Define E°

Answer 24

the p.d. of a half cell relative to a standard hydrogen electrode, with all concentrations at 1moldm-3 and gases at 1atm

Question 25

What are E(cell) and E°(cell) measured at

Answer 25

measured under zero current with a high resistance voltmeter

Question 26

What does E(cell) > 0 mean for favourability

Answer 26

favourable

Question 27

which is the anode, which is the cathode, and which way would electrons flow if the voltmeter were replaced with a wire

Answer 27

-Cl has higher +Ve so is at the cathode -Fe is lower so is anode **Cathode on the left, anode on the right. Electrons from right to left**

Question 28

write the cell diagram

Answer 28

Question 29

Resistance is measured in Ω. What are alternative units

Answer 29

R = V/I V A-1

Question 30

Define resistance

Answer 30

How difficult it is to get current to flow through something

Question 31

If a wire is thinner, is the resistance higher or lower

Answer 31

higher

Question 32

resistance and voltage in series and in parallel

Answer 32

voltage split in series and same in parallel resistance is added in series and 1/Rt = 1/R + 1/R in parallel

Question 33

For resistors in parallel, what share of the voltage will the second diagram have

Answer 33

higher resistance= higher voltage to get the electrons through

Question 34

Why in an experiment do you want less current

Answer 34

less internal resistance/ heating of wires

Question 35

Silver to silver chloride is easier than H2 cells to measure against even though it is 0.22V. Why is this

Answer 35

makes AgCl which is insoluable, so don't need to separate half cell

Question 36

Avagdros constant

Answer 36

6.022 x 10^23

Question 37

What is the ΔG equation for a cell

Answer 37

ΔG = -nFE(cell) n = number of moles of electrons per mole of the reaction as written * F = Faraday’s constant = 96500 C mol-1

Question 38

How to calculate ΔG° (can be used to work out E°)

Answer 38

ΔG° = -nFE°(cell) or ΔG° = -RT ln K

Question 39

What equation relates ΔG° and the equillbrium constant

Answer 39

ΔG° = -RT ln K

Question 40

What does the circle represent ΔG°

Answer 40

standardisation

Question 41

ΔG° = -nFE°, explain with the table how the values of each constituent effects wether a reaction is spontaneous

Answer 41

Question 42

cathode- anode/ most positive- most negative. If the difference between the two values say about how favourable a reaction is

Answer 42

higher difference= more favourable

Question 43

Which will be the reactants and which are the products

Answer 43

Question 44

What happens to the equilibrium when you add more reactants

Answer 44

Adding reactant (Eg Cu2+) or removing product (eg Zn2+): equilibrium will move L→R. L→R direction more favourable; ΔG↓ E(cell)↑

Question 45

Answer 45

Question 46

slide 69

Question 47

What is the Nerst equation 𝐸 𝑐𝑒𝑙𝑙 =

Answer 47

Question 48

What is an equation relating E° to the equilibrium constant K

Answer 48

Question 49

What is the equation for K

Answer 49

Question 50

If the G of a reaction A --> B is positive, then what could this insinuate

Answer 50

A ---> B is unfavourable, so reaction can happen in reverse so B --->A is favourable

Question 51

Why are all the reactants and products in standard state if Q=1

Answer 51

In (1) is zero, and so -RT/nf becomes 0

Question 52

Calculate the E cell value of this hydrogen half cell

Answer 52

Question 53

What is the PANCakes abbreviation for a Electrolytic cell/ doesn't always work with galvanic

Answer 53

Postive = anode negative = cathode

Question 54

What is the abbreviation An Ox, Red Cat

Answer 54

anode = oxidation cathode= reduction

Question 55

In a reaction E cell and G cannot have the same value

Question 56

n= number moles of electrons per mole of the reaction as written

Answer 56

Question 57

What voltage needs to be given to drive an unfavourable reaction

Answer 57

At least the same as the cell potential E(cell); If you apply exactly E(cell), no reaction happens. So you want to apply "over potential" to make sure the reaction actually goes (Note: not E°; use Nernst / concentrations) **E(applied)- E(cell)= over potential**

Question 58

How to work out the solubility constant (uses activities)

Answer 58

Question 59

how would you work out the activities of Pb2+ and 2Cl

Answer 59

[conc]/1M

Question 60

How dissolving PbCl2 in a solution of NaCl, reduce the solubility of PbCl2 using the common ion effect

Answer 60

s= conc of dissolved lead(II) chloride NaCl and PbCl2 have Cl- ions in common. 1.If extra chlorine is added to the equilibrium it will shift to the left and make more PbCl2. 2.However, conc of Pb ions is so small so only small amount of Cl can be converted 3. **PbCl become less soluble** 4. and the **conc of Pb ions in solution decreases**

Question 61

What type of substances does the common ion effect occur to

Answer 61

occurs with any **sparingly soluble substance**: it is less soluble in a solution which contains any ion which it has in common

Question 62

When PbCl is dissolved in water there are less/more of its ions in solution than when dissolved in NaCl

Answer 62

more PbCl ions when dissolved in water. Ions from PbCl is going to be tiny compared with the NaCl solution. In calculations with NaCl and PbCl, it can be assumed that the conc of the common ion Cl is entirely due to NaCl

Question 63

Answer 63

ksp= [Ca][SO4] if s= conc of Ca (Ca and SO4 concs are the same) 2.4x10^-5 = s2 so s=4.9 x 10^-5 moldm-3

Question 64

Answer 64

conc would be lower due to common ion effect

Question 64

Answer 64

conc would be lower due to common ion effect

Question 65

Answer 65

Question 66

Answer 66

Question 67

what are the assumptions in an "ideal solution"

Answer 67

Question 68

Answer 68