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[OBSELETE] Edexcel - A Level Chem > Topic 14 > Flashcards

Topic 14 Flashcards

1
Q

How do you setup an electrochemical cell?

A
  1. OBtain metals and clean to remove impurities
  2. Wash metals with propanone and place into solutions with the same ion
  3. Make a salt bridge with filterpaper soaked in saturated KNO2 or KCl linking the two beakers
  4. Connect the electrodes to a voltmeter and power source
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2
Q

What is redox?

A
  • Reduction = Gain of electrons
  • Oxidation = Loss of electrons
    OIL RIG
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3
Q

What are reducing agents?

A
  • They are oxsidised themselves
  • Loose electrons
  • Helps reduce another atom
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4
Q

What is a oxsidising agent?

A
  • Reduces itself
  • Gains electrons
  • Helps oxsisdise other substances
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5
Q

What are half cells?

A
  • One half of a chemical cell
  • Constructed of a metal dipped in its ion
  • OR a platinum electrode with 2 aqueous ions
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6
Q

What reactions occur in an ion half cell?

A

Fe2+ + 2e- <-> Fe

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7
Q

Why do we use a platinum electrode?

A
  • Its inert but electrically conductive
  • It allows for electricity to travel up electrode and into next cell
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8
Q

What happens in an electrochemical cell?

A
  • One side undergoes reduction the other oxidation
  • Redox reaction
  • Voltmeter find the Ecell / EMFwhich is the pd between the two
  • Elecrons flow from a less reactive metal to the more reactive cell
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9
Q

What is the standard electrode potential?

A
  • Voltage produced from a standard half cell connected to a hydrogen half cell
  • Standard hydrogen half cell = 0V
    • Needed to compare other half cells
  • Under standard conditions
    • 298K
    • 100 kPa
    • 1 mol dm-3 conc of ions
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10
Q

What does the standard hydrogen potential look like?

A
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11
Q

How do you work out EMF?

A
  • Use the electrode potentials of each half cell
  • EMF = Reduced - Oxidised
    • Larger V = Reduced
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12
Q

What is the setup for a non metal and metal half cell

A
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13
Q

What happens when a copper half cell and a hydrogen half cell is turned on

A
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14
Q

What is cell notation?

A
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15
Q

How can you predict feasibility using standard electrode potential?

A
  • Work out standard EMF
    • Reduced - Oxidised
  • If the value is positive it is reduced
  • The reaction is feasible
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16
Q

What is the E cell directionally proportional to?

A
  • Proportional to the total entropy
  • And to lnK for a reaction
17
Q

What effects the standard electrode potential

A
  • Different conditions effect the position of equilibrium
  • IF equilibrium changes, cell potential value changes too
  • Standard conditions are used allowing for comparisons
18
Q

Why may a reaction that is calculated to be feasible not occur?

A
  1. reactants are KINETICALLY STABLE which means that the reaction would have a high activation energy -> rate of reaction would be too slow
  2. non standard conditions
19
Q

What is a electrochemical series?

A
  • A list of electrode potentials
  • Allowing for you to find them in the data booklet
  • Calculate EMF (Reduced - Oxidised)
20
Q

How can you work out the feasibility of a disproportionation reaction using standard electrode potential?

A
  1. Identify which half equation has been oxidised (more negative)
  2. Reverse equation and combine half equations to obtain a feasible reaction
  3. Calculate E cell to calculate feasibility
21
Q

What are the half equations in the Lithium ion cell?

A
22
Q

What is the setup for a hydrogen fuel cell?

A
23
Q

What are the steps in hydrogen fuel cells?

A
  1. Hydrogen is fed into the left side
    1. Reacts with OH- (2H + 4OH → 4H2O +4e-)
  2. Electrons produced travel through platinum electrode
    1. Intert but conductive
  3. Flow of electrons power somthinG
  4. Oxygen fed into cell
    1. Reacts with water + e- made from step 1
    2. O2 + 2H2O +4e- → 4OH
  5. Cathode (-) e- flow to electrode
  6. Electrolytes (KOH) carries OH- ions made to anode
  7. E- flow from anode (+)
  8. Water is eliminated and released into surroundings
  9. OH- ions from step 4 carried to anode via eletctrode
24
Q

What are alcohol fuel cells

A

###

  • Uses for methanol and ethanol
  • Reforms them to use hydrogen
  • Alcohol is oxidised at the anode with water present
    • CH2OH + H20 → CO2 + 6e- + 6H+
  • H+ ions then pass through electrode
    • 6H+ + 6e- + 1.52 → 3H2O

[OBSELETE] Edexcel - A Level Chem (27 decks)

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