Redox - Topic 3 Flashcards
what is an oxoanion
an ion with a general formula of XOy- .e.g SO3^2-
X represents any element whilst O represents oxygen
oxidation numbers rules
1) oxidation number of uncombined elements is zero
2) in ions made of just one atom the oxidation number of the element is the charge of the ion
3) the sum of oxidation numbers is zero
4) the sum of oxidation numbers for one ion is the charge of the ion
5) same elements have fixed oxidation numbers in all their compounds
exceptions of oxidation numbers
- Carbon is +4 in CO2 (but is usually -4)
- H is -1 in metal hydrides
- O is +2 in OF2 (when combined with fluorine) and in peroxides its -1
- Cl, Br, I is +1 when bonded to O or F (as F is more electronegative)
F is always -1 as it is the most electronegative
rules for naming inorganic compounds
- the ending ‘ide’ shows that the compound contains two elements, the most electronegative element comes second
- roman numerals indicate the oxidation numbers of the element
- oxoacids end in ic our ous e.g HNO3 or H2S03 (sulphurous acid), the ic ending is apart of the compound with the highest oxidation number
- ending for salts from oxoacids are ate an ite such as sulfate SO4 2- or sulfite S03 2-
what are oxidising agents
substances that oxidise other species by removing their electrons causing them to gain electrons and hence are reduced themselves
what are reducing agents
chemical reagents that Donate electrons causing the reduction of other species and get hence get oxidised themselves
what are disproportionation reactions
where an element in a single species is being simultaneously oxidised and reduced
what happens during halogen displacement
the most oxidising halogen will displace the less oxidising halogen to form a solution of its salt
e.g
Cl2 (aq) + Br2- (aq) —-> 2Cl- (aq) + Br2
Cl2 (aq) + I2- (aq) —-> 2Cl- (aq) + I2
trend of oxidising power down group 7
the oxidising power decreases as you go down the group
