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Chemistry 30 AP > Chapter 14: Electrochemical Cells: > Flashcards

Chapter 14: Electrochemical Cells: Flashcards

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1
Q

What is an electric cell?

A

A device that continuously converts chemical energy to electrical energy.

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2
Q

What is a battery?

A

A group of 2 or more electric cells connected to each other in series.

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3
Q

What is an electric cell composed of?

A

An electric cell is typically composed of 2 electrodes (solid metal conductors) and 1 electrolyte (aqueous electrical conductor).

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4
Q

What are the names of the positive and negative electrodes?

A

Cathode (+) and Anode (-).

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5
Q

What is electricity?

A

The flow of electrons.

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6
Q

What is electric potential difference, or voltage?

A

The energy difference per unit charge measured in volts (V).

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7
Q

What is the voltage of a cell depend on?

A

The chemical composition of the reactants inside the cell.

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8
Q

What is electric current?

A

Measured by an ammeter in amperes (A), it is a measure of the rate of flow of charge.

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9
Q

How is voltage affected by an increase in cell size?

A

It is not affected since it is the ratio of energy to charge.

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10
Q

What is the effect of an increase in cell size on electric current?

A

The greater the cell size, the greater the current that can be produced by the cell.

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11
Q

How is charge measured?

A

The charge transferred by a cell/battery is measured in coulombs (C) and expresses the total charge transferred by the movement of charged particles.

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12
Q

How do electrons flow in an electric cell?

A

Electrons in an electric cell from through the external circuit from anode to the cathode.

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13
Q

What are primary cells?

A

Cells that cannot be recharged.

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14
Q

What are secondary cells?

A

Cells that can be recharged by using electricity to reverse the chemical reaction that occurs when electricity is produced by the cell.

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15
Q

What are fuel cells?

A

Cells that produce electricity by the reaction of a fuel continuously supplied to keep the cell operating. Fuel cells (such as hydrogen/oxygen fuel cell) generate energy more efficiently and without producing greenhouse gases, unlike the burning of fossil fuels.

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16
Q

What is a voltaic cell?

A

An arrangement of 2 half-cells separated by a porous boundary.

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17
Q

What is a porous boundary?

A

A physical barrier that separates 2 electrolytes while permitting ions to move between the 2 solutions. This salt bridge maintains electrical neutrality of the 2 solutions by doing this.

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18
Q

What is a half-cell?

A

An electrode-electrolyte combination forming one half of an electric cell.

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19
Q

What to look into?

A

pg.623, and search online/in labs experimental evidence of electric cells in action.

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20
Q

What happens at the cathode of a voltaic cell?

A

The cathode is where reduction occurs.

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21
Q

What happens at the anode of a voltaic cell?

A

The anode is where oxidation occurs.

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22
Q

What is the SOA doing in a voltaic cell?

A

In a voltaic cell, the strongest oxidizing agent undergoes reduction at the cathode (since electrons flow from anode to cathode).

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23
Q

What is the SRA doing in a voltaic cell?

A

In a voltaic cell, the strongest reducing agent undergoes oxidation at the anode.

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24
Q

What is an inert electrode?

A

An unreactive solid conductor in a cell that provides a location to connect a wire and a surface on which a half-reaction can occur.

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25
Q

Why can ionic compounds not be used as electrodes?

A

Because they do not conduct electricity.

26
Q

How do anions move as a voltaic cell operates?

A

Anions move towards the anode.

27
Q

How do cations move as a voltaic cell operates?

A

Cations move towards the cathode.

28
Q

How do the solutions change, charge-wise, as a voltaic cell operates?

A

The solutions remain electrically neutral, thanks to the porous boundary.

29
Q

What is cell notation outline?

A

anode | electrolyte || electrolyte | cathode

30
Q

What is standard cell potential (E^deg cell)?

A

The maximum electric potential difference (voltage) of a cell operating under standard conditions; E^deg cell represents the energy difference between the cathode and the anode. Degree sign implies 1.0mol/L and SATO conditions apply.

31
Q

What is standard reduction potential (E^deg r)?

A

This value represents the ability of a standard half-cell to attract electrons/undergo reduction. In a competition for electrons, the half-cell with the more positive reduction potential gains electrons from the half-cell with the lower reduction potential.

32
Q

How is standard cell potential calculated?

A

Standard cell potential is the difference between the reduction potentials of the 2 standard half-cells (E^deg cell= E^deg cathode - E^deg anode).

33
Q

What is a reference half-cell?

A

A half-cell that is chosen as a reference and arbitrarily assigned an electrode potential of zero volts; it is a standard hydrogen electrode unless told otherwise.

34
Q

What does a positive cell potential indicate?

A

An E^deg cell>0 indicates that the net reaction is spontaneous- a requirement for all voltaic cells.

35
Q

What to remember when finding net cell potential?

A

Make sure cathode/anode reactions are opposite and adjust number of electrons if necessary (this doesn’t affect voltage- a ratio).

36
Q

What is corrosion?

A

An electrochemical process in which a metal reacts with substances in the environment, which returns the metal to an ore-like state. Because we live in an oxidizing (oxygen) environment, oxidation (corrosion) of some metals occurs spontaneously.

37
Q

What happens to a metal during corrosion?

A

As a metal is oxidized, it loses electrons to form positive ions.

38
Q

What are ‘noble’ metals?

A

Metals such as gold and silver are called ‘noble’ because they are weak reducing agents- they aren’t easily corroded/oxidized.

39
Q

What must be present for iron to rust/corrode?

A

The presence of oxygen AND water is required, and the iron is converted into iron hydroxides and oxides.

40
Q

What can accelerate the rusting of iron?

A

The presence of acidic solutions, electrolytes, mechanical stresses, and contact with less active metals.

41
Q

What is a simple protective coating?

A

Paint, if a surface is completely covered, is a simple method for corrosion prevention. Metallic coating is another choice.

42
Q

What is galvanization?

A

Zinc plating of steel/iron provides a protective layer and preferential corrosion of zinc (it is more easily oxidized).

43
Q

What is cathodic protection?

A

A method of preventing corrosion where the iron is forced to become the cathode by supplying the iron with electrons, using either an impressed current or a sacrificial anode.

44
Q

What is an impressed current?

A

An electric current forced to flow toward an iron object by an external electric power supply (aka external potential difference).

45
Q

What is a sacrificial anode?

A

When a metal more easily oxidized than iron is connected to an iron object so that this more active metal is slowly consumed at the anode, forcing iron to become the cathode of the cell. Zing plating/galvanizing is a common example of this.

46
Q

According to the redox spontaneity rule, what happens if the strongest oxidizing agent present is below the strongest reducing agent present?

A

If the SOA is below the SRA, no spontaneous reaction can occur (E^deg cell<0).

47
Q

What is an electrolytic cell?

A

A cell in which a non-spontaneous redox reaction is forced to occur; A combination of 2 electrodes, an electrolyte, and an external power source.

48
Q

What is electrolysis?

A

The process of supplying electrical energy to force a non-spontaneous redox reaction to occur.

49
Q

Which electrode is the cathode in a voltaic and electrolytic cell, respectively?

A

The cathode is the positive electrode in a voltaic cell, and the negative electrode in an electrolytic cell.

50
Q

What is the chloride anomaly?

A

Due to half-cell over-voltage, chlorine gas is produced instead of oxygen gas in situations where water and chlorine are the only reducing agents present.

51
Q

What is the chlor-alkali process?

A

The most important nonmetal produced by electrolysis is chlorine, and most it’s production is done through the chlor-alkali process. The chlor-alkali process is the electrolysis of aqueous sodium chloride to produce, chlorine (anode product) , hydrogen, and sodium hydroxide (cathode products).

52
Q

What is electrorefining?

A

When an electrolytic cell is used to obtain purified metals at cathode from impure metals at the anode.

53
Q

Why is it important to purify metals?

A

Impurities lead to a lower conductivity.

54
Q

What is electrowinning?

A

A method of purifying metals by reducing metal cations from a molten or aqueous electrolyte at the cathode of an electrolytic cell.

55
Q

What is electroplating?

A

A process in which a metal is deposited on the surface of an object placed at the cathode of an ELECTROLYTIC cell.

56
Q

How to figure out units if you forgot formula on test?

A

Look at formula sheet, it gives you terms and their units so find a way to cancel them out and get the units you want.

57
Q

What is charge, Q, in coulombs, determined by?

A

Electric current and time, It (units cancel out).

58
Q

What is faraday’s constant?

A

The quantity of chare transferred for every mole of electrons that flows in a cell is 9.65x10^4 C/mol.

59
Q

What is faraday’s law?

A

It states that the mass of an element produced or consumed at an electrode is directly proportional to the time the cell operates, as long as the current is constant.

60
Q

What is the formula for faraday’s law?

A

n(e-)=Q/F or n(e-)=It/F, where n is the moles of electrons, t is TIME IN SECONDS, and F is faraday’s constant.

61
Q

What not to forget when finding the amount of metal deposited or consumed in a given time?

A

After finding half-cell equation, MAKE SURE to convert moles of electrons to moles of metal using molar coefficients from equation.

Chemistry 30 AP (9 decks)

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