TEST CODE 02112020

FORM TP 2010149 MAY/JUNE 2010

CAR I B B EAN E XAM I NAT I O N S C O U N C I L

ADVANCED PROFICIENCY EXAMINATION

CHEMISTRY

UNIT 1 – Paper 02

2 hours 30 minutes

READ THE FOLLOWING INSTRUCTIONS CAREFULLY.

1. This paper consists of SIX compulsory questions in TWO sections.

2. Section A consists of THREE structured questions, one from each Module.

Section B consists of THREE extended response questions, one from each
Module.

3. For Section A, write your answers in the spaces provided in this booklet. For
Section B, write your answers in the answer booklet provided.

4. All working must be shown.

5. The use of silent, non-programmable calculators is permitted.

6. A data booklet is provided.

Copyright © 2008 Caribbean Examinations Council®.

All rights reserved.
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SECTION A

Answer ALL questions in this section.

Write your answers in the spaces provided in this booklet.

MODULE 1

FUNDAMENTALS IN CHEMISTRY

1. (a) State the types of bonds (intra-molecular and inter-molecular) that exist in liquid
ammonia.

_____________________________________________________________________

_____________________________________________________________________
[ 2 marks]

(b) Ammonia can be produced by heating calcium oxide with ammonium chloride. The
two other products are calcium chloride and water.

(i) Write a balanced chemical equation for the reaction between calcium oxide and
ammonium chloride.

_______________________________________________________________

_______________________________________________________________
[ 2 marks]

(ii) Calculate the mass of ammonium chloride needed to produce 1 dm 3 of

ammonia at RTP (room temperature and pressure).
(Molar volume = 24 dm3 at RTP)

[ 2 marks]

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(c) (i) Ammonia gas deviates from ideal behaviour. Under which of the following
sets of conditions, I, II or III, would the deviation be LEAST?

Temperature ( °C)
Conditions Pressure (kPa)

I 40 101
II 150 50
III 20 500

_______________________________________________________________
[ 1 mark ]

(ii) State TWO assumptions of the kinetic theory as it pertains to ideal gases.

______________________________________________________________

______________________________________________________________

______________________________________________________________

–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
[ 2 marks]

(iii) Which assumption of the kinetic theory as it pertains to ideal gases would MOST
likely account for your answer to (c) (i) above?

_______________________________________________________________

_______________________________________________________________
[ 1 mark ]

(d) Some ammonia gas is dissolved in water. The exact concentration of the solution is
unknown and has to be determined. Describe an experiment that would determine the
concentration of the aqueous ammonia.

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________
[ 5 marks]

Total 15 marks

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M ODULE 2

K IN ET IC S AN D E Q U IL IB R IA

2. (a) Define EACH of the following terms:

(i) Standard electrode potential of a half-cell

[ 2 marks]

(ii) Standard cell potential of an electrochemical cell

[ 2 marks]

(b) Figure 1 is a diagram of an electrochemical cell consisting of a standard copper

electrode and a standard aluminium electrode, represented by the notation,
Al(s) | Al3+(aq) || Cu2+(aq) | Cu(s).

17

Solution A Solution B

Figure 1. An electrochem ical cell with standard copper and alum inium electrodes

(i) On the diagram in Figure 1, label

a) the ions in Solution A and Solution B

b) the salt bridge

c) the cathode and anode

d) the direction of electron flow. [[ 5 marks]

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(ii) State what would be observed at the cathode after the electrochemical cell in
Figure 1 has been running for a few hours.

_______________________________________________________________
[ 1 mark ]

(iii) State the experimental conditions used in the preparation of the cell in Figure 1.

Temperature ____________________________________________________

Concentration of Solutions A and B _______________________________

_______________________________________________________________
[ 2 marks]

(iv) Use the information in your Data Booklet to calculate the standard cell potential,
Ecell, for the electrochemical cell in Figure 1.

[ 3 marks]

Total 15 marks

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MODULE 3

CHEMISTRY OF THE ELEMENTS

3. Ammonium vanadate(V), NH4VO3, is an orange solid. Tests are performed on NH4VO3 to show
the variable oxidation states of vanadium.

(a) Record in Table 1 the observation expected for EACH of the tests below.

TABLE 1: TESTS ON AMMONIUM VANADATE(V)

Test Observation Inference

(i) A few cm3 of bench NaOH Colour: __________________ VO2+ formed

is added to a small amount
of solid NH4VO3, followed
by a few cm3 of dilute
H2SO4 .

(ii) A little granulated zinc is Colour changes to

added to the solution in (i) ______________________ , VO2+ and VO2+
above. then to
______________________ , VO2+
then to

________________________________,
V3+
and finally
_______________________ V2+


[ 5 marks]

(b) Calculate the oxidation number of vanadium in EACH of the following species:

(i) VOSO4

_______________________________________________________________

(ii) VO2+

_______________________________________________________________

(iii) VO2+

_______________________________________________________________
[ 3 marks]

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(c) When concentrated HCl is added to a pink solution of cobalt(II) chloride, the solution
turns blue.

Give an explanation for the observation stated above in terms of the stability constant
of the complex ion formed, and write a balanced equation for the reaction.

Explanation

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

Equation

_____________________________________________________________________
[ 4 marks]

(d) Complete Table 2 to show the acid/base character of the oxides of Group IV elements
in the +2 oxidation state.

TABLE 2: OXIDES OF GROUP IV ELEMENTS

Group IV Oxides Acid/Base Character

CO (i)

CO2 (ii)

SnO Amphoteric

PbO (iii)

[ 3 marks]

Total 15 marks

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SECTION B

Answer ALL questions.

Write your answers in the separate answer booklet provided.

MODULE 1

FUNDAMENTALS IN CHEMISTRY

4. (a) Copy and complete Table 3, which provides information on the properties of the simple
subatomic particles.

TABLE 3: PROPERTIES OF SIMPLE SUBATOMIC PARTICLES

Particle Relative Mass Relative Charge Location

1
Electron –1 (i) _____________
1840

Proton (ii) ____________ +1 Nucleus

(iii) ____________ 1 (iv) ____________ Nucleus

[ 4 marks]

(b) (i) Radioactive emissions are affected by an electric field. Name the type of radio-
active particle that behaves in the same way as the electron. [ 1 mark ]

(ii) 216
Po decays by emitting β particles. State the product formed from the decay
84

of 216
Po by the emission of three β particles and calculate the n/p ratio of BOTH
84

the reactant and product atoms. [ 6 marks]

(iii) Comment on the effect that the decay has on the stability of the nucleus of
216
Po.
84
[ 1 mark ]

(c) (i) Draw the structures of the atomic orbitals of principal quantum number 2.
Include x, y and z axes in the drawing. [ 2 marks]

(ii) Using s, p, d notation, write the electronic configuration of 24Cr.

[ 1 mark ]

Total 15 marks

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MODULE 2

KINETICS AND EQUILIBRIA

5. A student prepares an ethanoic acid solution of pH 5. He uses this solution to make a buffer.

(a) Define EACH of the following terms:

(i) pH [ 2 marks]

(ii) Buffer solution [ 2 marks]

(b) The acid dissociation constant (Ka) of ethanoic acid at 25 °C has a numerical value
of 1.7 x 10-5. The equilibrium equation for the dissociation of ethanoic acid is

CH3COOH(aq) H+ (aq) + CH3COO–(aq).

(i) Write an expression for the acid dissociation constant (Ka) of ethanoic acid.
[ 1 mark ]

(ii) Calculate the equilibrium concentration of ethanoic acid in a solution that has
a pH of 5. [ 4 marks]

(c) State the effect, on the equilibrium position of a buffer solution, of adding small amounts
of

(i) H+ (aq) [ 1 mark ]

(ii) OH – (aq). [ 1 mark ]

(d) A buffer solution is made by adding 20.5 g of sodium ethanoate (CH3COONa) to

-5
500 cm3 of 1.5 mol dm–3 ethanoic acid. (Ka = 1.7 x 10 at 25 °C for ethanoic acid).

Calculate the pH of this buffer solution. [ 4 marks]

(Relative atomic mass: H = 1, C = 12, O = 16, Na = 23)

Total 15 marks

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MODULE 3

CHEMISTRY OF THE ELEMENTS

6. The elements in Period 3 of the periodic table are given below.

Na Mg Al Si P S Cl Ar

(a) Account for EACH of the following variations in properties across the period Na to
Ar.

(i) Electronegativity increases across the period. [ 2 marks]

(ii) Melting point of the elements increases from Na to Si. [ 2 marks]

(b) Describe the trend in the acid/base character of the oxides of the elements in Period 3.
[ 3 marks]

(c) When aluminium chloride dissolves in water, its solution is acidic. Account for the
acidic nature of the aluminium chloride solution. [ 2 marks]

(d) Transition metals have higher melting points than metals such as calcium in the s-block
of the periodic table. Suggest TWO reasons for this. [ 2 marks]

(e) P4O10 and PCl5 are the oxide and chloride of phosphorous in its highest oxidation state.

Write an equation to show how EACH of the following reacts with water.

(i) P4O10 [ 2 marks]

(ii) PCl5 [ 2 marks]

Total 15 marks

END OF TEST

02112020/CAPE 2010