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CHM 101 > ELECTROCHEMISTRY > Flashcards

ELECTROCHEMISTRY Flashcards

1
Q

State the electrochemical series of metal from most reactive to least reactive

A

Li, K, Ca, Na, Mg, Al, Zn, Cr, Fe, Ni, Sn, Pb, H2, Cu, Hg, Ag, Pt, Au

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2
Q

What is electrochemistry

A

It is the branch of chemistry that deals with the inter conversion of electrical and chemical energy

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3
Q

Metals are good oxidizing agents
True/ false

A

False

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4
Q

What are the types of electrochemical cells and what do they do

A

Voltaic/galvanic: produces electricity in a spontaneous reaction
Electrolytic cell: produces a chemical change in a non-spontaneous reaction

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5
Q

What is the anode

A

It’s the positive electrode of a cell, oxidation takes place there and electrons leave

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6
Q

What is a potentiometer

A

It is an instrument that measures the potential difference of a cell by generating a voltage equal to that of the cell

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7
Q

Relationship between Gibbs free energy and the electrode potential of a cell

A

When E is -ve, G is +ve
When E is +ve, G is -ve

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8
Q

What is the relationship between Gibbs free energy and spontaneity of a reaction

A

When G is -ve, reaction is spontaneous
When G is +ve, reaction is non spontaneous
When G = 0, reaction is at equilibrium

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9
Q

What is Gibbs free energy

A

It is the max useful work done by a system

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10
Q

What is the cathode

A

It is the negative electrode, reduction takes place, electrons enter the cell

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11
Q

What is electrolysis

A

Electrolysis is a process of driving a reaction in a non spontaneous direction by passing current through it

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12
Q

What are concentration cells and what is usually the electrode potential

A

They are volcanic cells with the same species on the two half cells but with different concentrations
E⁰ = 0

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13
Q

What are the differences between voltaic and electrolytic cells

A

The electron flow is reversed
The anode does opposite jobs
The cathode does opposite jobs

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14
Q

State faraday’s laws of electrolysis

A

1st law states that the mass of an element liberated during electrolysis is proportional to the quantity of electricity passing through the cell.

2nd law states that when the same quantity of electricity is passed through various electrolytes, the masses of the ions deposited at the electrode is directly proportional to their chemical equivalence

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15
Q

What are the factors that affect discharge of elements

A

The concentration of the ions in the electrolyte
The nature of the electrode
The position of the element in the electrochemical series

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16
Q

How do you calculate chemical equivalence

A

Molar mass/ number of moles of electrons needed

17
Q

Hall process

A

What is the electrolytic process of extracting aluminium from bauxite ( anhydrous Al2O3) called

18
Q

When do you consider concentration of ions over position in the electrochemical series in the preferential discharge of ions

A

You do that when the elements between them is two or less

19
Q

The more reactive/electropositive metals are more likely to be discharged during electrolysis
True/False

A

False

20
Q

What are electrodes

A

They are conductors through which electric current enters or leaves the electrolyte

21
Q

State the ionic theory

A

The ionic theory (by arrhenius) states that when an electrolyte is melted/dissolved in water, some or all of its molecules dissociate into freely moving charged particles(ions)

This process is called ionization

22
Q

What was the fault found in the ionic theory

A

It was discovered by x-ray diffraction that electrolytes contained these charged particles in them and are just separated when melted or dissolved

23
Q

What are inert electrodes

A

Inert electrodes are electrodes that do not take part in the electrolytic reaction

24
Q

Give examples of inert electrodes and what element attacks them

A

Platinum - chlorine
Carbon - oxygen

25
Q

State the electric series of non-metals in order of decreasing electronegativity/increasing preference for discharge

A

F, SO4^ -², NO3^-, Cl^-,Br ^-, I ^-, OH^-

26
Q

What are the electrodes used in the electrolysis of acidified water

A

Platinum foils

27
Q

What electrodes are used to in the electrolysis of copper ii tetraoxosulphate vi

A

Copper cathode and carbon anode

28
Q

The quantity of products liberated at the electrodes during an electrolysis is dependent on

A

The magnitude of the steady current passed
The time of flow of the steady current
The ionic charge of the liberated element

29
Q

What are the uses of electrolysis

A

Purification of metals
Extraction of elements
Production of important compounds or gases
Electroplating

30
Q

What are the electrodes and electrolyte used in the extraction of copper from its ore

A

Impure copper ore as anode
Pure copper plate as cathode
A copper salt as electrolyte

31
Q

What is the electrolytic cell in the industrial electrolysis of brine called

A

Kellner-solvay cell

32
Q

What are the factors that affect the electrode potential of a system

A

The overall energy change
The concentration of ions in the solution
The temperature

33
Q

What is standard potential of a metal

A

It is the potential difference set up between the metal and one molar solution of its ions at 25°C

34
Q

Metals higher in the series will be deposited in favour of those lower in the series
True/False

A

False

35
Q

Electrons flow from metals higher in the series to those lower.
True/False

A

True

36
Q

Metals higher than hydrogen in the electrochemical series are found in a free state in nature.
True/False

A

False

37
Q

What is corrosion

A

It is a process whereby a metal reacts with oxygen and moisture in its environment and gradually deteriorate

38
Q

What is the chemical formula for iron rust

A

Fe2O3.xH2O

39
Q

Why does zinc doem a better protective covering of iron than tin

A

When part of the zinc covering is broken and trioxocarbonate acids fill it up the zinc acts as anode as it is higher than iron and is dissolved instead of the iron but with tin the iron is the anode and is dissolved

CHM 101 (8 decks)

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