CH1 Flashcards
Definition of Redox reaction
A chemical reaction where oxidation and reduction occur at the same time
Reduction in term of Oxygen
Loses oxygen
Reduction in term of Hydrogen
gain hydrogen
Reduction in term of Oxidation number
Oxidation number decrease
Reduction in term of electron transfer
Gain electrons
Oxidation in term of Oxygen
Gains oxygen
Oxidation in term of Hydrogen
Loses hydrogen
Oxidation in term of Oxidation number
Oxidation number increases
Oxidation in term of electron transfer
loses electron
Oxidation number of Oxygen in peroxides
-1
Oxidation number of hydrogen in hydrides
-1
Electrochemical series
K Ca Na Mg Al Zn Fe Sn Pb H Cu Ag Au
5 Oxidising Agent
Acidified Potassium Manganate (VII)
Acidified Potassium Dichromate (VI)
Acidified Hydrogen Peroxide
Chlorine Water
Bromine Water
1 Famous Reducing agent
Reactive metals
Color of aqueous Chlorine
Pale Yellow
Color of aqueous Bromine
Brown
Color of aqueous Iodine
Brown
Color of in Chlorine 1,1,1-trichloroethane layer
Colourless
Color of in bromine 1,1,1-trichloroethane layer
brown
Color of in iodine 1,1,1-trichloroethane layer
Purple
Describe a chemical test to identify halogens
add 2cm3 of 1,1,1-trichloroethane to the test tube and shake gently.
Definition of electrode potential
Potential difference produced when an equilibrium is established between metal M and the aqueous solution containing metal Mn+ ions in a half cell.
Ion concentration at standard condition
1.0 mol dm-3
Gas pressure at standard condition
1 atm / 101kPa
temperature at standard condition
25c
Non metal inert electrode at standard condition
Platinum
Comparison between a larger and smaller standard electrode potential value
Element with larger E value is a stronger oxidising agent than with smaller E value
Ion of Element with larger E value has a greater tendency to receive electron to form atom
Ion of Element with larger E value undergoes reduction
Definition of electrolytes
Substances that can conduct electricity in either molten state or aqueous solution and undergoes chemical changes
Definition of Non-electrolytes
Substances that cannot conduct electricity in any state
An example of Non-electrolytes
Covalent compounds
2 examples of electrolytes
Ionic compounds in molten state
Acid & Alkali in presence of water
Particle that conduct electricity in an electrolyte
Ions
Subatomic particles that conduct electricity in a conductor
Electrons
Definition of electrolysis
A process whereby compounds in the molten state or aqueous solution decompose into their constituent elements by passing electricity trough them.
Change of energy on electrolytic cells
Electrical energy -> chemical energy
Change of energy in voltaic cells
Chemical energy -> electrical energy
Flow of cation in an electrolytic cells when electric current is passed trough
To cathode
Flow of antion in an electrolytic cells when electric current is passed trough
To Anode
Effect of more negative or less positive E0 value on electrolysis at anode
Anions easier to release electrons and be oxidised
Effect of less negative or more positive E0 value on electrolysis at cathode
Cations easier to receive electrons and be reduced
Effect of higher halide ions concentration on electrolysis at anode
Halide ions easier to release electrons and be oxidised
Effect of active electrodes on electrolysis at anode
No anions are discharged
Metal atoms at the anode releases electrons to form metal ions
Explain electroplating of metals through electrolysis
Electroplated object-cathode
Electroplating metal-anode
Electroplating metal ions-Electrolytes aqueous solution
Extraction method for metals more reactive than carbon
Electrolysis
Extraction method for metals less reactive than carbon
Reduction by carbon
Extraction method for non reactive metals
No method. Exists as metal elements
Explain extraction of Aluminium
Extracted through electrolysis
Aluminium ore or Bauxite is purified into Aluminium oxide
Aluminium Oxide is melted down with cryolite to lower its melting point
Oxide ion oxidised at Anode
Aluminium Ion reduced at Cathode
Redox at Anode
Oxidation
Redox at cathode
Reduction
Explain extraction of Iron
Extracted through reduction by carbon
Iron ore (hematite), limestone and coke is heated up in a blast furnace
C + O2 -> CO2
C + CO2 -> 2CO
Coke, C and Carbon Monoxide reduce Iron (iii) Oxide to Molten iron ( and produces carbon dioxide)
Explain extraction using more reactive metal
When heated together, more reactive metal reduces less reactive metal from its metal oxide
Metals are produced in molten state due to large amounts of heat released
Definition of metal corrosion
Redox reaction when metal is oxidised spontaneuosly when metal atoms release electrons to form metal ions
Relation between electropositivity of metal and tendency to corrode
More electropositive, more easier to corrode//rust
