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Chemistry Chapter 9 > Chapter 9.2 and 19.1 > Flashcards

Chapter 9.2 and 19.1 Flashcards

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1
Q

Electrochemical Cells

What are the 2 main types of electrochemical cells?

A

Volataic cells and electrolytic cells

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2
Q

Voltaic Cells

What are voltaic cells?

A

Generate electricity from chemical reactions

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3
Q

Voltaic Cells Generate Electricity from Spontaneous

How is the voltaic cell set up?

A

Seperate the 2 half equations into 2 half cells allowing electrons to flow through circuit

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4
Q

Half-Cells Generate Electrode Potentials

What is a half cell made of?

A

It is made of a single metal strip inserted in solution of its ions

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5
Q

Half-Cells Generate Electrode Potentials

What is an electrode potential?

A

The charge separartion betweeen the the metal and its ions in solution

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6
Q

Half-Cells Generate Electrode Potentials

Which metal will have a more negative electrode potential?

A

The more reactive metal, as it will act as a better reducing agent meaning that the electrons removed will remain on the metal strip creating a negative charge on it.

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7
Q

Two Connected Half-Cells Make a Voltaic Cell

What will result if the 2 half cells are connected via a wire?

A

The electrons will flow

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8
Q

Two Connected Half-Cells Make a Voltaic Cell

What is the name of the electrode where oxidation occurs?

A

Anode and has a negative charge

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9
Q

Two Connected Half-Cells Make a Voltaic Cell

What is the name of the electrode where reduction occurs?

A

Cathode and has positive charge

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10
Q

Two Connected Half-Cells Make a Voltaic Cell

What should be connected at the 2 electrodes?

A

An external electronic circuit that is attcahed to a voltmeter. This will lead to the flow of electrons to go from anode to cathode

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11
Q

Two Connected Half-Cells Make a Voltaic Cell

What should be connected between the 2 half cells

A

A salt bridge

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12
Q

Two Connected Half-Cells Make a Voltaic Cell

What is a salt bridge and what is it made out of?

A

A glass tube or strip of absorptive
paper that contains an aqueous solution of ions

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13
Q

Two Connected Half-Cells Make a Voltaic Cell

How is the flow of ions through the salt bridge

A

Movement of these ions neutralizes
any build-up of charge and maintains the potential difference. Anions move in the
salt bridge from the cathode to the anode, which opposes the flow of electrons in the
external circuit. Cations move in the salt bridge from the anode to the cathode.

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14
Q

Cell Diagram Convention

What does the single vertical line mean in the cell diagram convention?

A

Represents a phase boundary such as that between a solid electrode and an aqueous solution within a half-cell

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15
Q

Cell Diagram Convention

What does a double vertical line mean

A

Presence of salt bridge

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16
Q

Cell Diagram Convention

Where are the aqueous solutions of each electrode placed?

A

Next to salt broidge

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17
Q

Cell Diagram Convention

How are the anodes and cathodes placed?

A

By convention anode is placed on the left and cathode on the right

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18
Q

Different Half-Cells Make Voltaic Cells with Different Voltages

What will the direction of electron flow and voltage produced be dependent on?

A

Difference in reducing strength of the two metals, judged by the relative position of the metals in the reactivity series

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19
Q

Standard Electrode Potentials

What is the SI unit of electric current (I)?

A

amp(A)

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20
Q

Standard Electrode Potentials

What is the SI unit of electric charge (Q)

A

coulomb (C)

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21
Q

Standard Electrode Potentials

What is electric charge?

A

The amount of
charge transported in 1 second by a current of 1 ampere

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22
Q

Standard Electrode Potentials

What is Faraday (F)?

A

96485.34 C/mol

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23
Q

Standard Electrode Potentials

How can the equation Q=I × t be written?

A

C = A × s

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24
Q

Standard Electrode Potentials

What is the charge of an electron?

A

1.602 × 10(to the power of -19)

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25
Q

Standard Electrode Potentials

What is the unit of potential difference?

A

volt (V)

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26
Q

Standard Electrode Potentials

What is the electromotive force of a cell (EMF)

A

The greatest potential difference
that it can generate. It is measured in volts.

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27
Q

Comparisons of Half-Cell Electrode Potentials need a Reference Point

What is the reference standard used to measure the reducing powers of of half-cells?

A

Standard hydrogen electrode (SHE)

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28
Q

The Standard Hydrogen Electrode

What electrode is used in the SHE?

A

Platinum is used as the conducting metal in the electrode because it is fairly inert and
will not ionize, and it also acts as a catalyst for the reaction of proton reduction

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29
Q

The Standard Hydrogen Electrode

What is the structure of the SHE?

A

Glass tube where 100 kPa of H2 gas is inserted and has holes in order to allow H2 gas to escape. This glass tube is immeresed in a beaker conatining acid solution of 1 M H+

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30
Q

The Standard Hydrogen Electrode

What is the electrode potential assigned to SHE?

A

The standard hydrogen
electrode is assigned
an electrode potential
value of 0 V.

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31
Q

Measuring Standard Electrode Potentials

What are the standard conditions which should be met in order to compare different half cells?

A

-all solutions must have a concentration of 1.0 mol dm–3
-all gases must be at a pressure of 100 kPa
-all substances used must be pure
-temperature is 298 K
-if the half-cell does not include a solid metal, platinum is used as the electrode.

32
Q

Measuring Standard Electrode Potentials

What are the name of cells under standard conditions?

A

Standard half cells

33
Q

Measuring Standard Electrode Potential

How is the standard electrode potential generated?

A

When the standard hydrogen electrode is connected to another standard half-cell
by an external circuit with a high-resistance voltmeter and a salt bridge

34
Q

Measuring Standard Electrode Potential

What does a positive value for the standard electrode potential mean?

A

This means that the half cell has a greater tendency to be reduced

35
Q

Measuring Standard Electrode Potential

What does a negative value for standard electrode potential mean?

A

It has a lower tendency to be reduced

36
Q

Standard Electrode Potentials are Given for the Reduction Reaction

What are standard electrode potential values also known as?

A

Standrad Reduction Potentials

37
Q

Standard Electrode Potentials are Given for the Reduction Reaction

What are some points that should be noted about the standard electrode potential values?

A

-the values refer to the reduction recation
-the values do not depend on total number of electrons
-the more positive the value is, the more readily is it reduced

38
Q

Standard Electrode Potentials are Given for the Reduction Reaction

How do electrons flow in a voltaic cell?

A

Through external circuit from electrode with more negative standard electrode potential to electrode with more positive electrode potential

39
Q

Using Standard Electrode Potential Data

How is the cell potential calculated?

A

E *cell = E half-cell where reduction occurs – Ehalf-cell where oxidation occurs

40
Q

Using Standard Electrode Potential Data

How can the spontaneity of reaction be determined?

A

-If E * cell is positive, the reaction is spontaneous as written.
-If E * cell is negative, the reaction is non-spontaneous, and the reverse reaction is
spontaneous.

41
Q

Using Standard Electrode Potential Data

How are E *
cell and the free energy, delta G * related?

A

delta G * = – nFE *
-n = number of moles of electrons transferred in the reaction
-F = the charge carried by 1 mole of electrons, known as the Faraday constant (it has a
value of approximately 96 500 C mol–1)
delta G * (J) = –n (mol) F (C mol–1) E * (V) as J = C × V

42
Q

Using Standard Electrode Potential Data

How can the powers of oxidizing and reducing agnets be compared?

A

A metal is able to reduce the ions of another metal that has a higher E * value. Metals with
low E * values (most negative) are therefore the strongest reducing agents. Likewise, a
non-metal is able to oxidize the ions of another non-metal that has a lower E * value.
Non-metals with high E * values are therefore the strongest oxidizing agents

43
Q

Using Standard Electrode Potential Data

What is the relationship between the E * of the half cell and the stregth of oxidizing or reducing agent?

A

The higher the value
of E * of a half-cell, the
stronger the oxidizing
agent; the lower the
value of E *, the stronger
the reducing agent

44
Q

Electrolytic Cells

What is an electrolytic cell?

A

It uses an external source
of electrical energy to
bring about a redox
reaction that would
otherwise be nonspontaneous

45
Q

Electrolytic Cells

What is electrolysis?

A

It is the process where
electricity is used to
bring about reactions of
chemical breakdown.

46
Q

Electrolytic Cells

What is the electrolyte?

A

The reactant in the process of electrolysis is present in electrolyte, which is a liquid,
usually a molten ionic compound or a solution of an ionic compound

47
Q

Electrolytic Cells

Where do the redox reactions occur in an electrolytic cell?

A

Redox reactions occur at the electrodes,
removing the charges on the ions and forming products that are electrically neutral.
The ions are therefore said to be discharged during this process

48
Q

Electrolytic Cells

What is the difference between electrodes and electrolytes?

A

Electrodes are
electronically
conducting, electrolytes
are ionically conducting

49
Q

Electrolytic Cells

What is the power source used in a electrolytic cell?

A

A battery or a DC power source

50
Q

Electrolytic Cells

What are the electrodes made of?

A

A conducting substance –
generally a metal or graphite

51
Q

Electrolytic Cells

How are the electrodes connected to each other?

A

By electric wires

52
Q

Electrolytic Cells

How is the movement of electrons in a electrolytic cell?

A

The power source pushes electrons towards the negative electrode where they enter
the electrolyte. This is the cathode. Electrons are released at the positive terminal,
the anode, and returned to the source. The current is passed through the electrolyte,
not by electrons but by the ions as they are mobile and migrate to the electrodes

53
Q

Redox Reactions Occur at Electrodes

How do the ions in the electrolyte travel to electrodes?

A

By attraction of opposite forces. So positive ions (cations) are attracted to the negative electrode, the cathode, while
negative ions (anions) are attracted to the positive electrode, the anode

54
Q

Redox Reactions Occur at Electrodes

What are the redox rections that happen at electrodes?

A

Oxidation at anode and reduction at cathode

55
Q

Redox Reactions Occur at Electrodes

What are the signs of the anode and cathode in an electrolytic cell?

A

Anodes are positively charged and cathodes are negatively charged

56
Q

Determining Products of Redox Reactions

What are the steps followed in order to deteremine product of redox reaction?

A
  1. Identify all the ions present in the electrolyte and determine which will migrate to which electrode: anions to anode, and cations to cathode.
  2. Where there is more than one possible reaction at each electrode, determine which will occur. Write the half-equation for the
    reaction at each electrode, showing electrons released at the anode in oxidation and taken up at the cathode in reduction.
  3. Balance the electrons lost and gained at the anode and the cathode, then add the two half-equations to write the equation for the net reaction.
  4. Consider what changes would be observed in the cell
    as a result of the redox processes occurring. These may
    include colour changes in the electrolyte, precipitation of solid, gas discharge, or pH changes.
57
Q

The Electrolysis of Molten Salts

What happens in the electrolysis of molten salts?

A

The only ions present are those from the
compound itself as there is no solvent. So, usually, only one ion migrates to each
electrode

58
Q

Electrolysis of Aqueous Solutions

What is water reduced to?

A

H2 (Page 447)

59
Q

Electrolysis of Aqueous Solutions

What is water oxidized to?

A

O2 (Page 447)

60
Q

Electrolysis of Water

What is added to water to increase its conductivity?

A

Ionic compounds such as NaOH

61
Q

Electrolysis of Water

What are the ions present in NaOH and where do they migrate to?

A

Na+(aq) to cathode and OH–(aq) to anode

62
Q

Electrolysis of Water

Whata are the possible reactions at the cathode? and what is preferentially reduced?

A

Page 448

63
Q

Electrolysis of Water

Whata are the possible reactions at the cathode? and what is preferentially reduced?

A

Page 448

64
Q

Electrolysis of Water

What are the possible reactions that occur at anode? and what is preferentially oxidized?

A

Page 448

65
Q

Electrolysis of Water

What is the overall balanced equation?

A

Page 448?

66
Q

Electrolysis of Water

What are possible changes observed at electrode?

A

-colourless gas evolved at both anode (O2) and cathode (H2)
-ratio by volumes of the gases is 2 H2 : 1 O2
-the pH at the anode will decrease as H+ is released, while the pH at the cathode
will increase as OH– is released.

67
Q

Electrolysis of NaCl

What is the entire process of the electrolysis of NaCl?

A

Page 449

68
Q

Electrolysis of CuSO4

What is the entire process of the electrolysis of CuSO4

A

Pge 450

69
Q

Selective Discharge

What does selective discharge depend on?

A

Relative E * values, the ion
concentration, and the
nature of the electrode.

70
Q

Factors Affecting the Amount of Product in Electrolysis

What did the amount of product depend on according to Micheal Faraday?

A

Quantity of electric charge passed through the cell, the duration as well as charge

71
Q

Factors Affecting the Amount of Product in Electrolysis

How can the amount of produxt be determined?

A

Find charge C, then use Faraday equation to find C/mol, then use molar ratio to find number of moles, then use molar mass to determine mass of product

72
Q

Electroplating

What is electroplating?

A

The process of using electrolysis to deposit a layer of a metal on top of another metal or other conductive object

73
Q

Electroplating

What are the features of electroplating?

A

-an electrolyte containing the metal ions which are to be deposited
-the cathode made of the object to be plated
-sometimes the anode is made of the same metal which is to be coated because it may
be oxidized to replenish the supply of ions in the electrolyte.

74
Q

Electroplating

What happens in the process of electroplating?

A

Reduction of the metal ions at the
cathode leads to their deposition
on its surface.

75
Q

Electroplating

What are possible uses for electroplating?

A

-Decorative purposes
-Corrosion control
-Improvement of function

Chemistry Chapter 9 (2 decks)

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