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A level Chemistry > Redox > Flashcards

Redox Flashcards

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1
Q

in a peroxide ?

A

O = -1

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2
Q

redox =

A

reduction reaction + oxidation reaction

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3
Q

oxidation number?

A

no. of electrons, lost gained or shared when an element reacts

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4
Q

half reactions overall give

A

ionic equation

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5
Q

oxidising agent?

A

are reduced, CAUSING OXIDATION

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6
Q

Reducing agent?

A

are oxidised, CAUSE REDUCTION

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7
Q

Can’t do half equations when

A

molecules involved bc no e- transfer

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8
Q

when reactions are in aq solution?

A

• H20, H+ present so use these to balance

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9
Q

to get overall eq?

A
  • e- number must be same in each equation

* cancel anything that comes up on both sides

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10
Q

if O bonded to F?

A

no longer -2

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11
Q

if H is in a hydride?

A

no longer +1

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12
Q

No. of change in ox =

A

no of change in reduction

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13
Q

balance using Ox numbers?

A
  • balance spectator ions last

* if 2 of the species (little no.) , x2 the number of change

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14
Q

A half cell

A

element in 2 diff oxidation states

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15
Q

electrode potential symbol

A

Eθ

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16
Q

Why is an inert electrode needed when there is an ECC w ions in diff ox states?

A

e.g. Pt or C bc no solids so can’t just dip crocodile clips into solution

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17
Q

how are SEP measured?

A

by connecting half cells to a SHE and measuring the PD

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18
Q

Half cells can be combined to form?

A

an electrochemical cell

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19
Q

salt bridge?

A
  • connects the 2 solutions allowing ions to be trans between 2 half cell, completing the circuit
  • doesn’t react w solutions in half cells
  • KNO3 (aq) usually, has to have a conducting solution
20
Q

the more + value is the

A

reduction

21
Q

conc of solutions in half cells?

A

1moldm-3

22
Q

SEP is

A

the tendency to gain e-

23
Q

SEP definition?

A

voltage of a half cell compared to SHE measured at 298K, 100kPa, 1 moldm-3

24
Q

eq to calc Eθcell?

A

Eθ positive -( Eθ negative)

or Eθ reduced - Eθ oxidised

25
Q

Eθ NOT

A

measured by mole, don’t multiply up

26
Q

when changing a conc look at

A

both equations!!

27
Q

Positive Eθ =

A

feasible

28
Q

⭐ can only change [] of

A

(aq) ions not solid

29
Q

how to work out the best reducing agent?

A
  • smallest E theta value

* least likely to be reduced

30
Q

oxidising/ reducing agent?

A

• write the right species e.g. for reducing agent write the thing that is ABOUT TO BE oxidised

31
Q

types of electrochemical cells?

A
  • used as cells and batteries
  • non-rechargeable cells
  • rechargeable cells
  • fuel cells
32
Q

lead-acid battery: negative electrode?

A

Pb

33
Q

lead-acid battery: positive electrode?

A

PbO2

34
Q

lead-acid battery: electrolyte?

A

Sulfuric acid

35
Q

one disadvantage of use lead acid battery in cars?

A
  • Pb is heavy
  • acid may leak out and corrode vehicle
  • may be no charge left in battery - may go flt
36
Q

what is a fuel cell?

A

an electrochemical device that combines hydrogen or a hydrogen rich fuel and O2 to produce electricity with water and heat as its by product

37
Q

Fuel cells: fuel

A
  • a log as fuel is supplied, fuel cell will continue to generate power - doesn’t need to be disposed of or recharged
  • Since the conversion of fuel to energy takes place via an ECC process not combustion, the process is clean (no CO2 produced), quiet and high efficient
38
Q

fuel cell overall equation

A

half equations for ox and red add together to give the same overall eq as combustion

39
Q

what is reduced in a fuel cell?

A

oxygen, at cathode to water

40
Q

what is oxidised in a fuel cell?

A

fuel , to CO2 at anode

41
Q

the fuel always

A

gets converted into CO2, but not if fuel is H2

42
Q

rechargeable and non-rechargable ECC are called

A

storage cells

43
Q

+ of rechargeable cell?

A

can be used many times

44
Q

+ of non- rechargeable cell?

A

cheaper

45
Q

+ of fuel cell?

A

efficent, clean and quiet

46
Q

fuels for fuel cell?

A
  • alcohol
  • alkanes
  • alkenes
  • hydrogen
47
Q

problem w hydrogen fuel cell?

A
  • H2 = explosive

* not universally available

A level Chemistry (39 decks)

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