redox Flashcards
what are the oxidation number rules for pure elements?
oxidation number = 0
as any bonding is to atoms of the same element so there is no difference in electronegativity
what are the oxidation number rules for simple ions e.g. Na+, Mg2+, Cl- ?
the oxidation number matches the charge of the ion (Na+ = +1, Mg2+ = +2, Cl- = -1)
what is the oxidation number rule for fluorine?
oxidation number = -1
what are the oxidation number rules for oxygen?
oxidation number = -2
oxidation number in peroxides = -1
oxidation number when bonded to Fluorine = +2 (as fluorine is more electronegative)
what are the oxidation number rules for hydrogen?
oxidation number = +1
oxidation number in metal hydrides = -1
what are the oxidation number rules for atoms in compounds and ions?
sum of oxidation numbers = overall charge
how do you work out oxidation number in a compound/ion?
sum of oxidation numbers = overall charge so use the oxidation number rules to find the known oxidation number, then use this to work out the unknown.
how are Roman numerals used in systematic naming?
iron(III) represents Fe3+ with oxidation number +3
iron(II) represents Fe2+ with oxidation number +2
how do you work out a formula using oxidation number e.g nitrate(III)?
NO2-, nitrate (III)
if oxygen is -2 and there are two of them, then the total charge for oxygen is -4. as NO2- has a 1- charge, nitrogen must be +3, so it is called nitrate(III)
define oxidation in. terms of electron transfer
oxidation is loss of electrons (OIL)
define reduction in terms of electron transfer
reduction is gain of electrons (RIG)
define oxidation in terms of changes in oxidation number
oxidation will cause the oxidation number to increase
define reduction in terms of changes in oxidation number
reduction will cause the oxidation number to decrease
metal + acid = ?
salt + hydrogen
name a specific reaction between a metal and dilute hydrochloric acid
zinc + dilute HCl
Zn increases by 2
each H decreases by 1 so the total decrease is -2
