Unit 3 - Redox Flashcards
what is the order of metals in a reactivity series?
(most to least reactive)
K Na Ca Mg Al C Zn Fe Sn Pb H Cu Ag Au Pt
Uses of Aluminium (properties and uses)
Properties: Light, low density and surface has already oxidised
Uses: Used to make alloys, tin foil and plane parts
Uses of Zinc (properties and uses)
Properties: soft, doesn’t oxidise
Uses: used to make alloys (brass), galvanization (acts as a self-healing layer and protects from oxidation)
Uses of Iron (properties and uses)
Properties: ductile, malleable, reactive, common, cheap, conductor, rusts easily
Uses: alloys (due to it being cheap and easy to work with)
Uses of Gold (properties and uses)
Properties: unreactive, soft, doesn’t oxidize
Uses: circuit bonds and jewelry
Uses of Copper (properties and uses)
Properties: malleable, ductile, and good conductor
Uses: wires and cooking items
Uses of Platinum (properties and uses)
Properties: soft and ductile and has a high melting point
Uses: catalysts
What is oxidation?
- Gain of oxygen atoms
- Loss of hydrogen atoms
- Loss of electrons
- Increase in oxidation state
What is reduction?
- Loss of oxygen atoms
- Gain of hydrogen atoms
- Gain of electrons
- Decrease in oxidation state
oxidation and reduction involving hydrogen or electrons (acronym)
OIL RIG:
Oxidation is loss
Reduction is gain
What are polyatomic ions?
A set of two or more atoms that are covalently bonded that have a net charge that isn’t zero.
Phosphate
(molecular formula + charge)
PO4 3-
Sulphate
(molecular formula + charge)
SO4 2-
Carbonate
(molecular formula + charge)
CO3 2-
Nitrate
(molecular formula + charge)
NO3 1-
Hydroxide
(molecular formula + charge)
OH 1-
Ammonium
(molecular formula + charge)
NH3 1+
What is an oxidising agent?
The thing being reduced
(allows something to be oxidised)
What is a reducing agent?
The thing being oxidised
(allows something to be reduced)
What kind of compounds do reactive metals make?
Stable compounds
(the more reactive a metal the more stable its compound)
What is electrolysis?
The use of electricity to decompose/split an electrolyte
What is electrolysis used for?
To split ore into individual elements and extract metals
What happens at the anode (+)?
Oxidation (loss of electrons)
What happens at the cathode (-)?
Reduction (gain of electrons)
What is the formula for moles?
moles = mass/molar mass
What is the formula for concentration?
concentration = moles/volume
What is the formula for percentage yield?
percentage yield = actual yield/ theoretical yield x 100
What does it mean if the oxidation state of an atom changes?
Oxidation/reduction is taking place
What does it mean if the oxidation state of an atom doesn’t change?
There is no oxidation or reduction taking place, but the reaction still takes place
What is the total oxidation state of a molecule?
0 in a neutral molecule
If the molecule has a charge (ion) then the total oxidation state will equal the overall charge
What is the oxidation state of an atom in elements (O2, H2, Cu2, etc.)
0
What is the oxidation state of oxygen?
-2
(except in O2 or FO2)
What is the oxidation state of group 1 metals in compouds?
+1
What is the oxidation state of group 2 metals in compounds?
+2
What is the oxidation state of hydrogen in compounds?
What are the exceptions?
+1
but:
0 if it’s as an element
-1 if in a compound with group 1-2 metals
What is the oxidation state of Flourine?
-1
(except in F2)
What is a single displacement reaction?
A chemical reaction in which one element is replaced by another in a compound
What is needed for a single displacement reaction to take place?
The element must be more reactive than the metal in the compound
Which of these displacement reactions will take place and which one will not react? Why?
- Al + CuSO4
or - Cu + AlSO4
- Will take place
- Will not take place
This is because aluminium is more reactive than copper. For the reaction to occur, the more reactive elements need to be alone (not in a compound)
What is a spectator ion? What are some examples of this?
Atoms that don’t participate in the reaction. They do not oxidise or reduce and their oxidation state doesn’t change.
What is the process of aluminium extraction?
- Bauxite Mining:
- Bauxite = aluminium ore
- found in tropical regions (like Brazil)
- extracted through open-pit mining.
- is then later purified into aluminium oxide - Electrolysis:
- electrolysis of aluminium oxide
- Al3O2 is dissolved in cryolite which reduces the operating temperature
- the liquifying of the aluminium oxide allows the ions to move freely
- due to the electricity flowing, the positive (3+) aluminium ions flow to the cathode and reduce, sinking to the bottom of the container since it has a higher density
- the negative (2-) oxygen ions flow to the anode and oxidise, reacting with the graphite/carbon and escape as CO2 gas bubbles
- this happens because opposites attract (positive aluminium attracted to negative cathode and negative oxygen attracted to positive anode)
What is the reaction taking place at the anode?
O2 (2-) —> O2 + 4e-
and
C + O2 —> CO2
What is the reaction taking place at the cathode?
Al (3+) + 3e- —> Al