Cambridge International AS Level Chemistry
Answers to end-of-chapter questions
Answers to EOCQs
Chapter 12
1
a Br2[1]
b chlorine before bromine;
[1]
bromine before iodine
[1]
c Iodine has the strongest intermolecular
forces / van der Waals' forces;
[1]
because it has most electrons / biggest
molecules.[1]
Total = 5
2 a i no reaction
[1]
ii no reaction
[1]
iii reaction[1]
iv reaction[1]
b iii Cl2(aq) + 2KBr(aq) → Br2(aq) + 2KCl(aq) [2]
[1 mark for correct formulae; 1 mark for
balancing]
iv Br2(aq) + 2NaI(aq) → I2(aq) + 2NaBr(aq) [2]
[1 mark for correct formulae; 1 mark for
balancing]
c displacement or redox
[1]
d strength as oxidising agent / reactivity is in
order Cl > Br > I[1]
e e.g. for iii: chlorine is reduced;
[1]
bromide ions are oxidised
[1]
–
–
f e.g. for iii: Cl2(aq) + 2Br (aq) → Br2(aq) + 2Cl (aq)
[1]
g Chlorine has a higher tendency to gain
electrons;[1]
as Cl atoms have smaller radius.
[1]
Total = 15
b precipitation:[1]
i white[1]
ii pale cream
[1]
iii yellow[1]
c only AgCl would dissolve
[1]
d AgCl and AgBr would dissolve
[1]
Total = 12
4 a i Cl2 + H2O → HCl + HOCl
[2]
ii oxidation numbers of Cl: 0 in Cl2; –1 in HCl;
+1 in HOCl
[3]
iii water treatment
[1]
b i Cl2 + 2NaOH → H2O + NaCl + NaOCl
[2]
ii oxidation numbers of Cl: 0 in Cl2;
–1 in NaCl; +1 in NaOCl
[3]
iii bleach[1]
c disproportionation[1]
Total = 13
3
a i AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
[2]
[1 mark for correct state symbols; 1 mark
for correct equation]
ii AgNO3(aq) + NaBr(aq) → AgBr(s) + NaNO3(aq)
[2]
[1 mark for correct state symbols; 1 mark
for correct equation]
iii AgNO3(aq) + NaI(aq) → AgI(s) + NaNO3(aq)[2]
[1 mark for correct state symbols; 1 mark
for correct equation]
Cambridge International AS and A Level Chemistry © Cambridge University Press 2014