redox
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what does reduction involve?
• the gaining of electrons • decrease in oxidation state
oxidation involves…
• the losing of electrons • increase in oxidation state
disproportionation is when…
the same substance undergoes both oxidation and reduction to form 2 diff products
when assigning oxidation no.s, the most __________ element is assigned the negative oxidation state
electronegative
what is the mnemonic for balancing equations? use mnemonic
EOHC – ew our hands clashed!
what are the 4 steps to balancing equations for substances in acidic medium?
E – balance Elements that are not O or H O – balance Oxygen by adding H2O H – balance Hydrogen by adding H+ C – balance Charge by adding e-
what doe BOD stand for?
biochemical oxygen demand
what is BOD?
the amount of O2 used up by aerobic bacteria to decompose the organic matter in a fixed volume of water over a period of usually 5 days at 293K
what does standard electrode potential mean?
the electromotive force generated by a half cell when measured against the standard hydrogen electrode at standard conditions of 298K, 1 bar of pressure, 1 moldm-3 electrolyte
standard electrode potential is also… (hint: potential)
potential difference
what is a voltaic cell?
a system in which chemical energy is converted to electrical energy through spontaneous redox reactions
what are the components of a voltaic cell?
• voltmeter • salt bridge • two half cells • connecting wires
what is the purpose of the salt bridge?
• maintain /charge neutrality • completes the electrical circuit
in a voltaic cell, electrons flow from the
anode to the cathode
in a voltaic cell, what happens at the anode?
oxidation
in a voltaic cell at the cathode, the electrolyte undergoes…
reduction
the anode in a voltaic cell is…
-ve
the cathode in a voltaic cell is _____
+ve
all half-cells electrode potential are measured against the ______________________
standard hydrogen electrode
what are the conditions the electrode potentials are measured at?
gases: 100kPa solutions: 1moldm-3 temp: 298K
the more +ve the Eº value, the more spontaneous the _________ reaction and the __________ the oxidising agent
reduction, stronger
the more -ve the Eº value, the more spontaneous the _________ reaction and the __________ the reducing agent
oxidation, stronger
what is the IUPAC convention for cell notation?
anode|R form|O form|salt bridge|O form|R form|cathode
what mnemonic can we use for cell notation?
EROSORE Electrode: Anode Red form Ox form Salt bridge Ox form Red form Electrode: Cathode