The introductory session for PACES chemistry 2009

1. PACES Chemistry
Purposeful Academic Classes Excelling Students
Purposeful Academic Classes Excelling Students
Wednesday 15th April 2009
Shenton College

2. Why are we here?

3. How can we benefit from
these sessions?

4. What resources are available
to help us maximise our
performance?

6. syllabus statement
✴
✴examiner’s report
✴past papers and solutions
✴revision books (eg Creelman,
Academic Associates etc)
teacher generated revision
✴
materials (ie from your school and
my podcasts and our forum page).

7. syllabus statement
✴
✴examiner’s report
✴past papers and solutions
✴revision books (eg Creelman,
Academic Associates etc)
teacher generated revision
✴
materials (ie from your school and
my podcasts and our forum page).

8. syllabus statement
✴
✴examiner’s report
✴past papers and solutions
✴revision books (eg Creelman,
Academic Associates etc)
teacher generated revision
✴
materials (ie from your school and
my podcasts and our forum page).

10. •Name
•School
•favourite ….?
•intended course and institution
•etc

11. My aims for today’s session:
look at effective use of the
✴
syllabus statement, and examiner’s
reports
investigate effective strategies
✴
for multiple choice, calculation and
extended answer style exam
questions.

12. Your suggestions for today:
extended answer questions
✴
✴bonding
✴electron configuration
✴calculation strategies
✴redox
✴electrochemistry
✴extended answer questions

13. 2008 examiner’s report
page 1 summary
page 2 structure
page 3 structure and general comments
page 4 specific comments (multi-choice)
page 5 specific comments (part 2)
page 6 specific comments (part 3)
page 7 specific comments (part 4)
pages 9 - 30 marking guidelines

27. 1.

28. 1.

29. 1.

30. 1.

31. 2.

32. 2.

33. 2.

34. 2.
All nitrates, and
potassium and sodium
salts are soluble and
colourless solutions
result. Any soluble
nickel salt produces a
green solution.

35. 2.
Calcium carbonate is
insoluble.

36. 2.
Cadmium carbonate is
insoluble.

37. 2.
Cadmium carbonate is
insoluble.

38. 3.

39. 3.
ie which would favour the forward reaction.

40. 3.
(a) adding a catalyst speeds up both forward
and reverse rates but doesn’t favour either
reaction.

41. 3.
(b) adding Ar(g) increases overall pressure, but
does not alter any of the individual gas
pressures (ie concentrations) and therefore has
no effect on equilibrium.

42. 3.
(c) increasing the pressure would increase the
concentrations of all gases, but would have a
greater impact on the product side and would
therefore favour the reverse reaction.

43. 3.
(d) increasing the temperature will alter the
equilibrium and favour the forward reaction.

44. 3.
(d) increasing the temperature will alter the
equilibrium and favour the forward reaction.

45. 4.

46. 4.
Text
Rate is decreased by decreasing pressure,
temperature, surface area, and use of an inhibitor.
Only alternative (a) satisfies these criteria.

48. 5.
6.

49. 5.

50. 5.

51. 5.

52. 5.

53. 5.

54. 6.

55. 6.

56. 6.

66. 2008 TEE multiple choice
examples

83. part 2 questions 2008 TEE

100. TEE part 3

101. a stan ard pro ure fo
d ced r
attem g chem
ptin istry
calculatio s
n
calculatio s in chem
n istry often
appear to be un ue an co plex
iq dm
… .

102. They m appear to be so ethin
ay m g
that yo ’ n t en un
uve o co tered
befo , but every calculatio type
re n
that yo w see in high scho l
u ill o
chem istry can be approached in
the sam w .
e ay

103. Step 1
I suggest that the first step in
an chem
y istry calculatio , after
n
balan g eq
cin uatio s, is to
n
determ e the n ber o m les o
in um fo f
an substan that yo can
y ce u .

104. Eg. Phosphoric acid can be made by the
following reaction:
Ca3(PO4)2(s) + H2SO4(aq) -> CaSO4(s) + H3PO4(l)
Balance the equation
b) How many grams of phosphoric acid can be
made by reaction of 155 g of Ca 3(PO4)2(s)
with more than enough (excess) sulfuric
acid?

105. Eg. Phosphoric acid can be made by the
following reaction:
Ca3(PO4)2(s) + 3H2SO4(aq) ->3CaSO4(s) + 2H3PO4(l)
Balance the equation
b) How many grams of phosphoric acid can be
made by reaction of 155 g of Ca 3(PO4)2(s)
with more than enough (excess) sulfuric
acid?

106. if you have the mass of a solid
you would use:
number of moles = actual mass ÷ molar mass
ie n = m/M

107. if you have the volume of a
solution you would use:
number of moles = concentration x volume
ie n = cv

108. if you have the volume of a gas
you would use:
n = PV/RT
or n = VSTP/22.41

109. Step 2
The seco d step yo sho em y
n u uld plo
is to use the ratio fromthe
chem ical eq uatio fo the reactio
nr n
to determ e the n ber o m les
in um fo
o the substan that yo n
f ce u eed to
fin o abo .
d ut ut

110. Step 3
The third step is to use the value
o the n ber o m les that yo
f um fo u
have just determ ed to w rk o
in o ut
the substan ’ m , vo e,
ces ass lum
co cen
n tratio etc.
n

111. Step 4
The fo urth step is to use the
substan ’ m , vo e,
ces ass lum
co cen
n tratio etc. to an er the
n sw
q uestio . ie % co po
n m sitio ,
n
em pirical fo ula etc
rm

112. mass
mass
vol (gas) vol (gas)
moles of moles of
moles of
known unknown
unknown conc &
conc &
vol
vol
from equation ratio
current
current
use formulae to determine n
usetime
& formulae
& time

113. Empirical and molecular formulae
DETERMINE TH NUMBER OF MOLES
E
Step 1
i. Start w an AMOUNT of each elem t.
ith en
(ie % or g)
ii. Convert the am t to gram of the elem t
oun s en
a.) if % convert to g in 100g
b.) if g of compound, convert to g of an element.
(eg C = 12.01g/44.01g in carbon dioxide
and H = 2.016/18.016g in water)
iii. Convert gram to m
s oles (molar masses)

114. Empirical and molecular formulae
COMPARE TH NUMBER OF MOLES
E
Step 2
i Look at the n ber of m
um oles of each elem t an find a
en d
ratio that relates them .
(Hint: divide each number of moles by the smallest number to
simplify the ratio.)
ii. Red uce to w hole integers
a.) round only 0.1 and 0.9
b.) multiply all others
(eg. 1.3 x 3 = 3.9 & 2.5 x 2 = 5)

115. Empirical and molecular formulae
ANSWER TH QUESTION
E
Step 3
i. Determine the empirical formula
If the compound is ionic then you have finished, but if it is a
molecular compound, then …..
Is a molar m given
ass ?
ii. If molar mass = empirical formula mass, then the
empirical formula is the molecular formula
iii. If the empirical formula mass is some multiple (x) of the
molar mass, then distribute the multiple (x) to the empirical
formula, to determine the molecular formula.

116. Empirical and molecular formulae
ANSWER TH QUESTION
E
Step 3
iv. Is any information on the no. of atoms given?
IF NO INFORMATION GIVEN ASSUME EF=MF

117. Empirical and molecular formulae
Hints:
-- always proceed down the process NEVER go backwards
-- do not round until the very end
-- all percentages must add to 100
-- the grams of all species present must total
to the mass of the compound present
-- make sure Ar not MW used in calculations
(eg. Ar(O) = 16, not 32)
-- make sure multiples of EF to MF distributed
properly (ex. 5CH2O = C5H10O5)

118. Empirical and molecular formulae
Problems:
A sample contains 71.65% Cl, 24.27%
C and 4.07% H. The molecular weight
is known to be 98.96 g/mol.
What are the empirical and molecular
formulas?

119. Empirical and molecular formulae
Problems:
A 0.1000 g sample of a compound
composed of C, H and O undergoes
combustion analysis. If 0.0928 g of
water and 0.288 g of carbon dioxide
are collected, what is the molecular
formula for the compound?

120. Extended answer style questions
ie part 4 of your exam.

121. 2007 TEE multiple choice
examples

126. 2007 TEE part 2
examples

146. 2007 examiner’s report
page 1 summary
page 2 structure
page 3 structure and general comments
page 4 specific comments (multi-choice)
page 5 specific comments (part 2)
page 6 specific comments (part 3)
page 7 specific comments (part 4)
pages 9 - 30 marking guidelines

159. 2007 TEE multiple choice
examples

164. 2007 TEE part 2
examples

181. 2007 TEE part 3