ELECTROCHEMISTRY Flashcards
State the electrochemical series of metal from most reactive to least reactive
Li, K, Ca, Na, Mg, Al, Zn, Cr, Fe, Ni, Sn, Pb, H2, Cu, Hg, Ag, Pt, Au
What is electrochemistry
It is the branch of chemistry that deals with the inter conversion of electrical and chemical energy
Metals are good oxidizing agents
True/ false
False
What are the types of electrochemical cells and what do they do
Voltaic/galvanic: produces electricity in a spontaneous reaction
Electrolytic cell: produces a chemical change in a non-spontaneous reaction
What is the anode
It’s the positive electrode of a cell, oxidation takes place there and electrons leave
What is a potentiometer
It is an instrument that measures the potential difference of a cell by generating a voltage equal to that of the cell
Relationship between Gibbs free energy and the electrode potential of a cell
When E is -ve, G is +ve
When E is +ve, G is -ve
What is the relationship between Gibbs free energy and spontaneity of a reaction
When G is -ve, reaction is spontaneous
When G is +ve, reaction is non spontaneous
When G = 0, reaction is at equilibrium
What is Gibbs free energy
It is the max useful work done by a system
What is the cathode
It is the negative electrode, reduction takes place, electrons enter the cell
What is electrolysis
Electrolysis is a process of driving a reaction in a non spontaneous direction by passing current through it
What are concentration cells and what is usually the electrode potential
They are volcanic cells with the same species on the two half cells but with different concentrations
E⁰ = 0
What are the differences between voltaic and electrolytic cells
The electron flow is reversed
The anode does opposite jobs
The cathode does opposite jobs
State faraday’s laws of electrolysis
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
What are the factors that affect discharge of elements
The concentration of the ions in the electrolyte
The nature of the electrode
The position of the element in the electrochemical series
How do you calculate chemical equivalence
Molar mass/ number of moles of electrons needed
Hall process
What is the electrolytic process of extracting aluminium from bauxite ( anhydrous Al2O3) called
When do you consider concentration of ions over position in the electrochemical series in the preferential discharge of ions
You do that when the elements between them is two or less
The more reactive/electropositive metals are more likely to be discharged during electrolysis
True/False
False
What are electrodes
They are conductors through which electric current enters or leaves the electrolyte
State the ionic theory
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
What was the fault found in the ionic theory
It was discovered by x-ray diffraction that electrolytes contained these charged particles in them and are just separated when melted or dissolved
What are inert electrodes
Inert electrodes are electrodes that do not take part in the electrolytic reaction
Give examples of inert electrodes and what element attacks them
Platinum - chlorine
Carbon - oxygen
State the electric series of non-metals in order of decreasing electronegativity/increasing preference for discharge
F, SO4^ -², NO3^-, Cl^-,Br ^-, I ^-, OH^-
What are the electrodes used in the electrolysis of acidified water
Platinum foils
What electrodes are used to in the electrolysis of copper ii tetraoxosulphate vi
Copper cathode and carbon anode
The quantity of products liberated at the electrodes during an electrolysis is dependent on
The magnitude of the steady current passed
The time of flow of the steady current
The ionic charge of the liberated element
What are the uses of electrolysis
Purification of metals
Extraction of elements
Production of important compounds or gases
Electroplating
What are the electrodes and electrolyte used in the extraction of copper from its ore
Impure copper ore as anode
Pure copper plate as cathode
A copper salt as electrolyte
What is the electrolytic cell in the industrial electrolysis of brine called
Kellner-solvay cell
What are the factors that affect the electrode potential of a system
The overall energy change
The concentration of ions in the solution
The temperature
What is standard potential of a metal
It is the potential difference set up between the metal and one molar solution of its ions at 25°C
Metals higher in the series will be deposited in favour of those lower in the series
True/False
False
Electrons flow from metals higher in the series to those lower.
True/False
True
Metals higher than hydrogen in the electrochemical series are found in a free state in nature.
True/False
False
What is corrosion
It is a process whereby a metal reacts with oxygen and moisture in its environment and gradually deteriorate
What is the chemical formula for iron rust
Fe2O3.xH2O
Why does zinc doem a better protective covering of iron than tin
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
