CAPE Chemistry 2008 U1 P2 Trinidad

Trinidad and Tobago

rESrcoDE 22112020

FORM TP 2008167

MAY/JUNE

CARIBBEAN EXAMINATIONS COUNCIL

ADVANCED PROFICIENCY EXAMINATION CHEMISTRY

{]NIT1-PAPER02 2 hours 30 minutes

READ THE FOLLOWING INSTRUCTIONS CAREFT]LLY.

1.

This paper consists of SIX compulsory questions in TWO sections.

2.

SectionA consists of THREE structured questions, ONE from each Module. Section B consists of TTIREE extended response questions, ONE from each Module.

3.

For SectionA, write your answers in the spaces provided in this booklet. For Section B, write your answers in the separate answer booklet provided.

4.

ALL working MUST

5.

The use of non-programmable calculators is permitted.

6.

A data booklet is provided.

be shown.

Copyright @ 2OO7 Caribbean Examinations Council All rights reserved.

22n2020tcAPElF 2008

@

2OO8

I

-2-

a-

SECTION A

i

--

AnswerALL questions in this section. Write your answers in the spaces provided in this booklet. MODIJLE

I

f-

1

I I

I

FTJNDAMENTALS IN CHEMISTRY 1.

(a)

(i)

Define the term 'standard enthalpy of formation', A Hre

t

r I

.

I

I

r'I I

II

[ 2 marks]

(iD

, I t

The enthalpy of formation of both carbon monoxide and aluminium oxide cannot be determined directly by experimental means. Suggest ONE reason in EACH case for the above observation.

CO:

Alror: [ 2 marks] (b)

Figure I shows the energy level diagram for determining the enthalpy of solution of KBr.

L

t AHs

Figure 1. Energy level diagram for determining the enthalpy of solution of KBr

GO ON TO THE NEXT PAGE 22l,r2Q20tCAPE/F 2008

-J-^

(D

writetheenthalpy change represenred by

AH,

AH' Ar!

and

AHrinFigure l.

:

A4' AH,

:

[ 3 marks]

(iD

Calculate the enthalpy of solution for KBr, given the following information.

AH,=+672kJmol

I

AHr=-656kJmol

I

[ 3 marks]

(c)

Table

I provides

data comparing the theoretical and experimental (Born-Haber) lattice X and Y.

energies of the halides of elements,

TABLE 1: THEORETICAL AND DPERIMENTAL LATTICE ENERGIES Compound

Theoretical lattice energy/[f mol-r

XCI XBr

-766 -731

XI

- 686

YCI YBr

-768 -759 -736

YI

Experimental lattice energy / lql mol-l

-776 -742 -699

- 890 -877 -867

What kind of bonding is present in

(D

halides of X?

(iD

halides of Y?

[ 2 marks]

GO ON TO TIIE NEXT PAGE 221r2020tCAPElF 2008

-4(d)

A studenr was required to design the method to be followed in determining the enthalpy of neutralisation of hydrochloric acid and sodium hydroxide.

,

Below is a reproduction of the shrdent's method.

tI

t

Measure 25 cm3 of hydrochloric acid (1M) into a plastic cup using a measuring

cylinder. Measure the temPerature of the acid. Transfer 35 cm3 of sodium hydroxide

r I

I

(lM) into

the plastic cup containing the hydrochloric acid. Stir gently with the thermometer and note the resulting temperature of the mixnue.

fI

t

r' I

Identify THREE errors in the above method.

{

(D

(ii)

(iiD

[ 3 marks]

Total 15 marks

t I

t

I I

L

f I

L-

r-

GO ON TO THE NEXT PAGE 22rr2020lcAPE/F 2008

i_

-)-

NOTHING HAS BEEN OMITTED

GO ON TO THE NEXT PAGE 22tt2020tcAPElF 2008

i

-6MODI]LE

:

2

KINETICS AND EQT]ILIBRIA

In order to determine the effect of concentration on reaction rates the reaction between butyl

t

chloride (C4HeCl) and water is investigated. C4HeCl (aq) +

fLO
+

i

C4HeOH (aq) + HCI (aq)

A

0.100 mol dm-3 aqueous solution of butyl chloride is reacted with water and the concentration measured at various time intervals to produce the results in Table 2.

i' I

I

TABLE 2: RESIIIJTS OF REACTION OF BUTYL CHLORIDE WITH WATER

fime, t

(a)

(s)

dmj

0.0

0.100

s0.0

0.090

1.91 x 10r

100.0

0.081

1.70 x

150.0

0.074

1.59 x lOa

200.0

o.067

300.0

0.055

500.0

0.037

600.0

0.030

800.0

0.020

L.4I x l0a 1.22 x lOa 0.801 x 104 0.620 x I}a 0.561 x 104

On the grid provided on page

7,

-axis.

s-1)

10.4

plot a graph of the concentration of butyl chloride,

on the y -axis against time in seconds, on the x

(b)

Reaction rate (mol

ICTBCU (mot dm3)

[ColtCl]

[ 4 marks]

Using your graph, estimate the concentration of butyl chloride at t = 400

t

s.

Ilmark]

t

L L

I

GO ON TO TTIE NEXT PAGE 22rr2020tcAPElF 2008

-7

-

GO ON TO THE NEXT PAGE 22tr2020tcAPElF 2008

-8 i-'

(c)

In addition to concentration, catalysts and temperature also affect reaction rates.

:

Using suitable well-labelled diagnms, explain how EACH of the following affects reaction rates:

i

r" I

(D

I

Catalysts

I

I

T I I

t

t

[ 4 marks]

L L

t

L

GO ON TO T}IE NEXT PAGE 22rr2020tcAPElF 2008

-9(ii)

Temperature

[ 4 marks]

(d)

NameTWO industrial processes in which catalysts are used.

[ 2 marks]

Total 15 marks

\ l l

GO ON TO TTM NEXT PAGE 22tt2020tcAPElF 2008

l0MODI,ILE 3 CHEMISTRY OF TIIE ELEMENTS

(a)

(D

Insert arrows in EACH of the boxes in Figure 2 to show the electronic configuration of the sPecies.

FeZ*

(Ar)

Mn2*

(Ar)

Cr Cu

(Ar) (Ar)

znz*

(Ar)

I

E E E E E 4s

3d

L]

Figure 2. Electronic configuration of different species ( 5 marks)

(iD

Explain EACH of the following statements in terms of electronic configurations.

a)

Fe2* ions are readily oxidized to Fe3* ions.

b)

Mn2* ions are NOT readilv oxidized to Mn3* ions. t

L

c)

t

Zn is NOT considered to be a transition element.

t [ 3 marks]

L i

GO ON TO TTIE NEXT PAGE 22rr2020tcAPElF 2008

i

- 11 (b)

Figure 3 refers to the following reaction scheme.

[Co(NH3)6]2+

(c)

CoCl2(s)

+

[Co(H2O)5]2

(B)

(A)

[CoClal2-

(D)

Figure 3. Reaction scheme

(i)

Complete the table below by writing the colour of the species labelledA, B, C and D. Species

A

B

C

D

Colour [ 4 marks] (iD

State the reagent used for the conversion in Reaction

I (D -+ B).

[1mark]

(c)

hon forms a complex ion with cyanide ions (CN-). The formula of the complex is [Fe(CN)u]

a-.

Explain how an aqueous solution of iron(Il) sulphate functions as an antidote for cyanide poisoning.

[ 2 marksJ Total 15 marks

I j

I

'

GO ON TO TIIE NEXT PAGE 22lt2020lcAPElF 2008

t2SECTION B

AnswerALL questions in this section. Write your answers in the answer booklet provided. MODULE

1

FI]NDAMENTALS IN CHEMISTRY 4.

(a)

t'

ListTHREE assumptions made about gas molecules in the kinetic theory.

t

[ 3 marks] (b)

The ideal gas equation is

PV =

(i) (ii) (c)

(d)

t

nRT.

Carefully explain the deviations produced by real gases.

Sketch a graph of volume (V) against the inverse of pressure (1/P) for of moles of an ideal guN at constant temperature.

(i)

l

TWO conditions under which the ideal gas equation adequately describes the behaviour of gases. [ 2 marks] State the

[ 3 marks] a constant number

Ilmark]

An organic compound, X contains carbon, hydrogen and oxygen only. When vapourised at 101 kPa and 373

K

1.00 g of

Y occupies

a volume of 667 cm3.

Calculate the mass in grams of I mole of Y. (Gas constant, R = 8.314 J K-l mol-l).

[ 4 marks]

(iD

On combustion in excess oxygen, 1 mole of Y produces carbon dioxide and water in the mole ratio 2:3. Deduce the formula of Y. [ 2 marks]

Total 15 marks

t

L

t l

GO ON TO THE NEXT PAGE 22tt2020tcAPElF 2008

-13 MODI]LE

2

KINETICS AND EQT]ILIBRIA 5.

Buffer solutions are prepared by mixing

a

weak acid or

a

weak base with a salt of that acid or base. (HCaH5O3) and 0.12 mol dm-3

A buffer solution is prepared using 0.14 mol dm-3 lactic acid sodium lactate (NaCrHrOr). K" = 1.4 x lOa for lactic acid. HCrHrOr(aq) + IIO(I)

(a)

=iHrO+(aq)

+ CrHrOr-(ag)

With reference to the Bronsted-Lowry theory explain EACH of the following:

(i) (iD

Weak acid Strong acid

[ 2 marks]

(b)

Describe the significance of pH

(c)

Calculate the pH of the HCaHsO3 / CaH5O3- buffer solution.

(d)

\ilith

(e)

When preparing a buffer solution of a specific pH, state ONE consideration into account in selecting a suitable weak acid.

(- log tH*l)

and

K" (acid dissociation constant) values. [ 2 marks] [ 4 marks]

the aid of balanced equations, explain how the HcaH5o3/ caHso3- buffer works in maintaining its pH. t 6 marksl

to

be taken

Ilmark]

Total 15 marks

GO ON TO THE NEXT PAGE 22rr2020tcAPElF 2008

-14MODIILE 3 i

CHEMISTRY OF THE ELEMENTS

T' I

I

(a)

Table 3 gives the atomic radii and melting points of the elements in Period 3.

I

r-

TABLE 3: SOME PROPERTIES OF ELEMENTS IN PERIOD 3

I

I

Atomic radius /nm Melting point / (i)

oC

CI

Mg

AI

Si

o.157

0.136

0.125

o.tr7

0.110

0.104

0.099

98

651

660

1410

M

tl4

-101

P

t'

t

State and account for the hend in the values of the atomic radii across the period

[ 4 marks]

from Na to Cl.

(ii)

s

Na

The trend in the melting points of the elements in Table 3 is related to structure and bonding. Describe the trend in the structure of the elements, and the trend in the bonding [ 5 marks] of the elements in Table 3.

(b)

(D

Compare the reaction of the Group

II

elements, Be and Ca, with water.

[ 2 marks]

(ii)

(c)

Describe what happens when barium is treated with water and write the equation [ 3 marks] for the reaction.

State ONE use of calcium carbonate.

Ilmark]

l

Total 15 marks t_

L

END OF TEST L

L

22tr2020tcAPElF 2008