Redox - Topic 3

Question 1

what is an oxoanion

Answer 1

an ion with a general formula of XOy- .e.g SO3^2-
X represents any element whilst O represents oxygen

Question 2

oxidation numbers rules

Answer 2

1) oxidation number of uncombined elements is zero
2) the sum of oxidation numbers is zero
3) the sum of oxidation numbers for one ion is the charge of the ion
4) aluminium is always +3
5) F is always -1 as it is the most electronegative

Question 3

exceptions of oxidation numbers

Answer 3

• Carbon is +4 in CO2 (but is usually -4)
• H is -1 in metal hydrides e.g NaH
• O is +2 in OF2 (when combined with fluorine) and in peroxides its -1 e.g H2O2
• Cl, Br, I is +1 when bonded to O or F (as F is more electronegative)

Question 4

rules for naming inorganic compounds

Answer 4

• 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-

Question 5

what are oxidising agents

Answer 5

substances that oxidise other species by removing their electrons causing them to gain electrons and hence are reduced themselves

Question 6

what are reducing agents

Answer 6

chemical reagents that Donate electrons causing the reduction of other species and get hence get oxidised themselves

Question 7

what are disproportionation reactions

Answer 7

where an element in a single species is being simultaneously oxidised and reduced

Question 8

what happens during halogen displacement

Answer 8

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

Question 9

trend of oxidising power down group 7

Answer 9

the oxidising power decreases as you go down the group

Question 10

Rules for balancing half equations

Answer 10

1) write down the species before and after the reaction
2) balance oxygen with H2O
3) Balance hydrogen with H+
4) Balamce charges with electrons