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FORM TP 2016166
TEST CODE
CARIBBEAN EXAMINATIONS
O2II2O2O
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MAY/JUNE 20I6
COUNCIL
CARIBBEAN ADVANCED PROFICIENCY EXAMINATION@
CHEMISTRY UNIT I -Paper02 2 hours 30 minutes
READ THE FOLLOWING INSTRUCTIONS CAREFULLY. I
This paper consists of SIX questions in TWO sections. Answer ALL questions.
2.
Write your answers in the spaces provided in this booklet.
J.
Do NOT write in the margins.
4.
Where appropriate,
5.
A data booklet is provided.
6.
You may use a silent, non-programmable calculator to answer questions.
7.
If you
need to rewrite any answer and there is not enough space to do so on the original page, you must use the extra lined page(s) provided at the back ofthis booklet. Remember to draw a line through your original answer.
8
If you
ALL WORKING MUST BE SHOWN in this booklet.
write the question number clearly in the box provided at the top of the extra page(s) and, where relevant, include the question part beside the answer, use the extra page(s) you MUST
DO NOT TURI\ THIS PAGE UNTIL YOU ARE TOLD TO DO
SO.
Copyright O 2015 Caribbean Examinations Council All rights reserved.
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4
SECTION A
AnswerALL questions. MODULE
1
FUNDAMENTALS IN CHEMISTRY
1.
(a)
John Dalton proposed the atomic theory in 1803.
(i)
State THREE postulates of Dalton's atomic theory.
[2 marks]
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5
(ii)
Later developments in science led to the modification of the atomic theory. Explain the modification of ONE of the postulates.
[2 marks] (b)
The dichromate(Vl) ion reacts in an acidic medium according to the following half-equation:
CrrO,2
(i)
(aq)
+ l4 H* (aq) + 6e- -------------->
2
Ct'.(aq) + 7 H,O(l)
Identify the ion responsible for the green colour.
I (ii)
mark]
Given that the sulfate(lV) ion, SO.2-, is converted to the sulfate(Vl) ion, SOo2 , in the presence of wateg deduce the balanced equation for the redox reaction between CrrOr2 (aq) and SOr'-.
[4 marksl
(iii)
Identify the oxidizing agent in (b) (ii).
[1 mark] GO ON TO THE NEXT PAGE
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-6(c)
The results of two tests are to be recorded in Table missing observations or inferences.
l.
Complete the table by inserting the
TABLE 1: RESULTS OFTESTS
(i)
(ii)
Inference
Observation
Test
Chlorine water is added to potassium bromide solution followed by aqueous silver nitrate.
Bromine water is added to potassium chloride solution followed by aqueous silver nitrate.
.
a
.
White precipitate formed
a
a
o
.
Br- oxidized to Br,
White precipitate formed on addition of AgNOr(aO)
a
[5 marks]
Total 15 marks
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MODULE
2
KINETICS AND EQUILIBRIA
2.
(a)
Define EACH of the following terms:
(i)
Weak acid
I (ii)
mark]
Ku
[2 marks]
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-8(b)
In aqueous solution, carbonic acid forms a weak acidic solution containing the hydrogen carbonate ion.
(i)
Write an equation to represent the dissociation of carbonic acid in aqueous solution
[2 marks]
(ii)
Write the K, expression for the reaction in (b) (i)
I (iii)
mark]
Calculate the pH of a 0.100 mol dm-3 aqueous solution of carbonic acid. (K":4.5 x l0-7 mol dm-3 at25 "C.)
[4 marks]
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-9(c)
A student was given a particular brand of club soda (carbonated beverage) to determine the carbonic acid content. Outline the experimental steps required for the investigation if the student is given 200 cm3 of 0.100 moldm-3 sodium hydroxide solution.
[5 marks]
Total 15 marks
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-10MODULE
3
CHEMISTRY OF THE ELEMENTS
3.
Figure
I
shows the melting points of the elements in Period
3
2000
I
1500
E
c
EL
1000
o0
E
o
500
0
NaMgAlSiPSCl
Ar
Figure 1. Melting points of elements in Period 3 (a)
Explain, in terms of structure and bonding, why
(i)
aluminium has a higher melting point than sodium
[2 marksl
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silicon has the highest melting point in the period
[2 marksl
(iii)
sulfur melts at a higher temperature than phosphorous.
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-12(b)
The reactions ofthe oxides of magnesium and phosphorous with waterare to be summarized
in Table 2.
TABLE 2: REACTION OF OXIDES WITH WATER Oxide
Reaction with Water
pH of Resulting Liquid
Mgo
Poo,o
(i)
Complete Table 2 by describing the reaction of EACH oxide with water and suggesting a pH value for the resulting liquid. [2 marks]
(ii)
Write the equation which represents the reaction of water with PoO,o.
[2 marksl
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Write equations to show what happens when EACH of the following chlorides reacts with water.
(i)
sicl4
::Ii+
NH i-Ei
.-E{ ---.r\:
]E -:.El .-'.E'
:I{ ---.*r-.
,rf,l
[2 marksl
(ii)
Alct3
[2 marksl
Total 15 marks
r]$ ,.._.+
..$. rl*l
:i(: '-'--'.--'--s-
,-:E :-.I*T
:ti. --Jx,l
:.!d 1fr: i-€i: ..Qi.
..e
..s
:G.
GO ON TO THE NEXT PAGE
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-14SECTION B
AnswerALL questions. MODULE
1
FUNDAMENTALS IN CHEMISTRY
4.
(a)
(i)
Describe how the bonds are formed in EACH of the solids, potassium chloride and iodine.
[4 marksl
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(ii)
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Complete Table 3 by comparing the physical properties of potassium chloride (KCl) and iodine (I,).
::.
TABLE 3: SOME PHYSICAL PROPERTIES OF KCI AND
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---l!*
:,'Iii
Properties Melting/Boiling point
KCI
l2
High
Low
Electrolyic conductivity
a
i:.€
:,:*
its i.fi Solubility in water
a
a
[2 marks]
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-16(b)
Account for EACH of the following statements:
(i)
.*-. .rii. .*i
The boiling point of HrO is higher than that of HrS
it*. :-ea-'. .'Jr1--
,:ts: it.iil
ikr :\-..I+-
-hi:tiiij
,:*:: rB---
!fui:
j€ii
iE .si
.a;
[3 marks]
(ii)
The molecules of aluminium fluoride in the presence of ammonia forms a white solid of formula NH3AlF3. (lnclude an appropriate equation in your account.) it+rl i'G-i
,R'l
iol is:
:.t ..Ei::,Sf
..H. :-}t+i:le-
[3 marks] GO ON TO THE NEXT PAGE
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(c)
-
-|
Explain the difference between the shapes of NH, and NHn*
[3 marks]
Total 15 marks
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MODULE
2
KINETICS AND EQUILIBRIA
The following equation represents the reaction between hydrogen and iodine.
5.
H,(g) + I,(g)
+
2
HI(g), AH: -10
kJ mol-l
The reaction is said to be in a state of equilibrium at a particular temperature and pressure.
(a)
(i)
State FOUR characteristics of a reaction
in'dynamic equilibrium'.
[4 marks]
(ii)
Write the expression for the equilibrium constant in terms of partial pressures, Ko, for the reaction shown by the equation above.
[2 marksl
(iii)
State TWO factors which would NOT affect the equilibrium of the reaction shown by the equation above.
[2 marks] GO ON TO THE NEXT PAGE
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Describe the effect of decreasing the temperature on
(i)
the equilibrium of the reaction
[2 marksl
(ii)
the value of K'p'
[2 marks] (c)
When 0.5 mol of hydrogen and 0.5 mol of iodine are allowed to reach equilibrium in a I .00 dm3 flask at 500 "C and l.0l x 105 N m-2, the amount of hydrogen iodide at equilibrium is 0.78 mol. Calculate K^ at 500 "C if the total pressure is I pa.
[3 marksl
Total 15 marks GO ON TO THE NEXT PAGE
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MODULE
3
CHEMISTRY OF THE ELEMENTS
(a)
6.
List FOUR properties of transition metals
[4 marks]
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(b)
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Titanium(Ill) chloride forms a violet solution when dissolved in water.
(i)
Write the electronic configuration using the s, p and d orbitals of the titanium ion
[1 mark]
(ii)
Explain the colour of the aqueous solution
[4 marks]
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-22(c)
(i)
Describe what would be observed when concentrated hydrochloric acid is slowly added to an aqueous solution of Co2*.
::]s
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.:.ft ni+
rla JIE:
.F
iIIj
iE ..I+
[1 markl
(ii)
jH .!ii
jfigl IFi.-
Write an ionic equation to represent the observation in (c) (i).
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,.4
[2 marksl
(iii)
Using the concept of stability constant, explain the changes observed in (c) (ii).
iE ifil --Gr
-\ ,!( .'* .t iH .-€! -:t
ts -.e
:..... ::+
,f(
::R ..{d .']'|r1
.-E :-trt
[3 marksl
Total 15 marks
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END OF TEST
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IF YOU FINISH BEFORE TIME IS CALLED, CHECK YOUR WORK ON THIS TEST.
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