Redox Flashcards
Oxidation
- gain of oxogen
- loss of hydrogen
- loss of electrons
- oxidation number increases
Reduction
- loss of oxygen
- gain of hydrogen
- gain of electrons
- oxidation number decreases
How to deduce oxidation states
the sum of the oxidation states must be 0
- fluorine is always -1
- chlorine is -1 unless it’s with oxygen or fluorine
- hydrogen is +1 unless in metal hydrides (NaH)
- the most electronegative atom gets the negative oxidation state
Oxidising agent
a substance that oxidises another (itself gets reduced)
Reducing agent
a substance that reduces another (itself gets oxidised)
Disproportionate reactions
a substance gets reduced and oxidised
Describe the activity series
metals at the top of the activity series are stronger reducing agents (more readily oxidised)
metals at the top of the activity series are weaker reducing agents (less readily oxidised)
What are the steps of a redox titration
1) calculate the n° of moles of oxidising agent
2) find the n° of moles of the oxidised substance
3) Calculate the mass of the oxidised substance
4) Calculate there % by mass
What is the biological oxygen demand
The amount of oxygen used by the aerobic microorganisms in water to decompose the organic matter in water over a fixed period of time
How to recognise an acidic solution equation
there is an oxygen imbalance
Outline how to balance an acidic solution equation
1) separate initial equation in 2 (oxidises vs reduced)
2) balance atoms except O and H
3) Balance O with water
4) Balance H atoms with H+
5) Balance the charge by adding electrons
Outline displacement reactions
more reactive gets oxidised
less reactive gets reduced
What are the units of the Winkler method
mg/dm3
How to calculate BOD
final dissolved oxygen content - initial dissolved oxygen content
What are the steps to calculate the dissolved oxygen content
1) determine the mols of XS2O3
2) deterine the mols of O2
3) determine the mass of O2
4) Determine the size of the sample in dm3
5) determine the concentration of dissolved oxygen
