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Chem year 1 > 137A- ions and electrochem > Flashcards

137A- ions and electrochem Flashcards

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1
Q

define voltage

A

energy per unit charge V=IR

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2
Q

What are other units for 1V

A

1J C-1

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3
Q

Equation for work

A

W= QΔV

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4
Q

define current

A

rate of flow of charge of electrons or ions

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5
Q

other units for current A

A

1Cs-1

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6
Q

charge on an electron or proton

A

+/-1.6 × 10-19 C

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7
Q
A
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8
Q

What is a redox reaction

A

about transfer of electrons between chemical species

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9
Q

What are the half equations for zinc and copper

A
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10
Q

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

A

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

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11
Q

What oxidation/reduction at the anode/cathode

A

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

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12
Q

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

A

Electrolytic- consumes electricity
Galvanic / Voltaic Cell- produces electricity

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13
Q

Draw hydrogen half cell

A
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14
Q

Write out the cell diagram equation

A
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15
Q

Write out the cell diagram equation

A
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16
Q

Write out the cell diagram equation

A
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17
Q
A

W= QV 2 x 5 = +10V

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18
Q
A

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

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19
Q

Draw the cell diagram for

A

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

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20
Q
A
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21
Q

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

A

anode. loose e- easier and are more easily oxidised

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22
Q

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

A

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

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23
Q

What is the equation for E cell

A

cathode- anode/ most positive- most negative

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24
Q

Define E°

A

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

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25
Q

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

A

measured under zero current with a high resistance
voltmeter

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26
Q

What does E(cell) > 0 mean for favourability

A

favourable

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27
Q

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

A

-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

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28
Q

write the cell diagram

A
29
Q

Resistance is measured in Ω. What are alternative units

A

R = V/I V A-1

30
Q

Define resistance

A

How difficult it is to get current to flow through something

31
Q

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

A

higher

32
Q

resistance and voltage in series and in parallel

A

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

33
Q

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

A

higher resistance= higher voltage to get the electrons through

34
Q

Why in an experiment do you want less current

A

less internal resistance/ heating of wires

35
Q

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

A

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

36
Q

Avagdros constant

A

6.022 x 10^23

37
Q

What is the ΔG equation for a cell

A

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

38
Q

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

A

ΔG° = -nFE°(cell) or ΔG° = -RT ln K

39
Q

What equation relates ΔG° and the equillbrium constant

A

ΔG° = -RT ln K

40
Q

What does the circle represent ΔG°

A

standardisation

41
Q

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

A
42
Q

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

A

higher difference= more favourable

43
Q

Which will be the reactants and which are the products

A
44
Q

What happens to the equilibrium when you add more reactants

A

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

45
Q
A
46
Q

slide 69

A
47
Q

What is the Nerst equation 𝐸 𝑐𝑒𝑙𝑙 =

A
48
Q

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

A
49
Q

What is the equation for K

A
50
Q

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

A

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

51
Q

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

A

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

52
Q

Calculate the E cell value of this hydrogen half cell

A
53
Q

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

A

Postive = anode
negative = cathode

54
Q

What is the abbreviation An Ox, Red Cat

A

anode = oxidation
cathode= reduction

55
Q

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

A
56
Q

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

A
57
Q

What voltage needs to be given to drive an unfavourable reaction

A

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

58
Q

How to work out the solubility constant (uses activities)

A
59
Q

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

A

[conc]/1M

60
Q

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

A

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

61
Q

What type of substances does the common ion effect occur to

A

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

62
Q

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

A

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

63
Q
A

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

64
Q
A

conc would be lower due to common ion effect

64
Q
A

conc would be lower due to common ion effect

65
Q
A
66
Q
A
67
Q

what are the assumptions in an “ideal solution”

A
68
Q
A

Chem year 1 (26 decks)

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