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PREPARATORY EXAMINATION VOORBEREIDENDE EKSAMEN

GRADE/GRAAD 12

SEPTEMBER 2014

PHYSICAL SCIENCES/FISIESE WETENSKAPPE

PAPER/VRAESTEL 2 (CHEMISTRY/CHEMIE)

MARKS/PUNTE: 150

TIME/TYD: 3 HOURS/UUR

This memorandum consists of 13 pages. Hierdie memorandum bestaan uit 13 bladsye.

Memo: PhySci P2/Fis Wet V2 Gr 12 2 FSDoE/VSDvO September 2014


QUESTION 1/VRAAG 1 1.1 B (2)

1.2 C (2)

1.3 C (2)

1.4 B (2)

1.5 D (2)

1.6 C (2)

1.7 A (2)

1.8 A (2)

1.9 C (2)

1.10 B (2) QUESTION 2/VRAAG 2 2.1 2.1.1 E (1)

2.1.2 C (1)

2.1.3 B (1)

2.1.4 G (1)

2.1.5 B & H (1) 2.2

2.2.1 3-methylpentanal 3-metielpentanaal (2) 2.2.2 4-ethylhex-2-yne 4-etielheks-2-yn OR/OF 4-ethyl-2-hexyne 4-etiel-2-heksyn (2) 2.2.3 2,4-dimethylhexane / 2,4-dimetielheksaan (2)

IF/INDIEN: Correct IUPAC name, but one or more of the following errors: omitting hyphens and/or commas; including extra spaces and/or hyphens Korrekte IUPAC-naam, maar een of meer van die volgende foute: weglating van koppeltekens en/of kommas; insluiting van ekstra spasies en/of

koppeltekens Max./Maks. 2

1



Marking criteria/Nasienriglyne:

Functional group Funksionele groep Whole molecule correct Hele molekuul korrek

IF/INDIEN:

Condensed or semi-structural formula: 2

1

Gekondenseerde of semistruktuurformule: 2

1

Molecular formula/Molekulêre formule: 2

0

C C C C

Br

H

H

H

Br H

C

H

H

H

H

H

H

C C O C C C

O H

H

H H

H

H

H

H

H

H

Marking criteria/Nasienriglyne: Functional group Funksionele groep Whole molecule correct Hele molekuul korrek

IF/INDIEN:

Condensed or semi-structural formula/ 2

1


1


0

2.3 2.31 (2) 2.3.2 (2) 2.4 2.4.1 Esterification / Verestering / Esterifikasie (1) 2.4.2 (2)

[18]


IF/INDIEN:


1


1


0

C C C C C

O H

H

H

C

H

H

H

H

H

H

H

H

H



Note/Let wel: No marks for: number of C atoms / chain length Geen punte vir: aantal C-atome / kettinglengte

QUESTION 3/VRAAG 3 3.1 3.1.1 Alkanes / Alkane (1) 3.1.2 Chain (isomerism) / Ketting(isomerisme) (1) 3.2 3.2.1 Branching / Vertakking (1) 3.2.2 Structure/Stuktuur:

From A to C/Van A na C: Branching decreases / molecules become less compact / surface area increases (over which intermolecular forces act). Vertakking verminder / molekule word minder kompak / oppervlak (waaroor intermolekulêre kragte werk) word groter. Intermolecular forces/Intermolekulêre kragte:

Stronger or more intermolecular forces / Van der Waals forces / dispersion forces / London forces.

Sterker of meer intermolekulêre kragte / Van der Waalskragte / dispersiekragte / Londonkragte. Energy/Energie:

More energy needed to overcome intermolecular forces / Van der Waals forces / dispersion forces / London forces. Meer energie benodig om intermolekulêre kragte / Van der Waalskragte /

dispersiekragte / Londonkragte te oorkom. 3.2.3 B Lowest boiling point / Laagste kookpunt (2) 3.3 3.3.1 London forces / Dispersion forces Londonkragte / Dispersiekragte (1) 3.3.2 London forces / Dispersion forces Dipole-dipole forces

Londonkragte / Dispersiekragte Dipool-dipoolkragte (2) 3.4 The hydrogen bonds between molecules of E

are stronger than the dipole-dipole forces between molecules of D. Die waterstofbindings tussen molekule van E is sterker as die dipool-dipoolkragte tussen molekule van D. (2)

[13]




ACCEPT/AANVAAR:-OH as condensed/ as gekondenseerd IF/INDIEN:


1


1


0

C C H

H

H

O

H

C

H

H

H

H

Marking guidelines/Nasienriglyne:

One mark for each correct structure./Een punt vir elke korrekte struktuur.

Accept molecular formula for H2./Aanvaar molekulêre formule vir H2.

Marking rule 6.3.10./Nasienreël 6.3.10.

Any additional reactants or products:/Enige addisionele reaktanse of produkte:

Max./Maks. 3

2

If arrow in equation omitted:/Indien pyltjie in vergelyking uitgelaat is: Max./Maks. 3

2

QUESTION 4/VRAAG 4 4.1 4.1.1 Addition / hydration Addisie / hidrasie / hidratering (1) 4.1.2 Substitution / halogenation / chloronation Substitusie / halogenasie / halogenering / chloronering (1) 4.1.3 Elimination / dehydration Eliminasie / dehidrasie / dehidratering (1) 4.2 4.2.1 H2SO4 / H3PO4 (1) 4.2.2

(2) 4.3 4.3.1 Hydration / Hidrasie / Hidratering (1) 4.3.2

(3)

C C C

H

H

H

H

H

H

+ H H C C C

H

H

H

H

H H

H

H



Time (s)

Ma

ss (

g)

(b)

Course of reaction / Reaksieverloop

Po

ten

tia

l en

erg

y /

Po

ten

sië

le e

ne

rgie

(J)

(a)

(d)

(c)

No labels on axis/Geen benoemings op asse: Max./Maks. 4

3

IF shape for endothermic reaction/INDIEN vorm vir endotermiese reaksie: 4

0


Correct shape/Korrekte vorm

(a) & (b) as shown/soos aangetoon

(c) as shown/soos aangetoon

(d) as shown/ soos aangetoon

4.4 4.4.1 2-chloropropane / 2-chloropropaan (2)

4.4.2 Sodium hydroxide / Potassium hydroxide Natriumhidroksied / Kaliumhidroksied (1)

4.4.3 Dilute base / Verdunde basis Mild heat / Matige hitte (2)

[15]

QUESTION 5/VRAAG 5

5.1 The concentration of hydrochloric acid decreases. Die konsentrasie van soutsuur verminder. (1)

5.2

(2) 5.3 Increases / Verhoog

At a higher temperature, more molecules have enough/sufficient kinetic energy / more molecules have kinetic energy greater than the activation energy. By 'n hoër temperatuur het meer molekule genoeg kinetiese energie / meer molekule het kinetiese energie hoër as die aktiveringsenergie.

More effective collisions per unit time/second. Meer effektiewe botsings per eenheidstyd/sekonde. (3)

5.4

(4)

Marking criteria/Nasienriglyne

Correct shape with decreasing gradient as shown./Korrekte vorm met afnemende gradiënt soos aangetoon.

Graph ends parallel to x axis and does not touch the x axis./Grafiek eindig parallel aan x-as en raak nie die x-as nie.




Substitution of volume and concentration of acid. Substitusie van volume en konsentrasie van suur.

Using ratio/Gebruik verhouding: (Mg) = ½n(HCℓ)

Substitution of 24 in M

mn /Substitusie van 24 in

M

mn

Initial mass/mole Mg – mass/mole Mg reacted Aanvanklike massa/mol Mg – massa/mol Mg gereageer

Final answer/Finale antwoord: 9,6 g

c = V

n

2 = 310100

n

n = 0,2 mol n(Mg reacted/gereageer) = ½n(HCℓ) = 0,1 mol

m(Mg reacted/gereageer):

n(Mg) = M

m

0,1 = 24

m

m = 2,4 g m(Mg) in excess/in oormaat: m = 12 – 2,4 = 9,6 g

n(Mg initially/aanvanklik):

n = M

m

= 24

12

= 0,5 mol n(Mg in excess/in oormaat): n = 0,5 – 0,1 = 0,4 mol m(Mg in excess/in oormaat):

n = M

m

0,4 = 24

m

m = 9,6 g

OPTION 2/OPSIE 2 OPTION 1/OPSIE 1

5.5 (5)

[15]



Wrong Kc expression/Verkeerde Kc-uitdrukking: Max./Maks. 8

5

QUESTION 6 6.1 Homogeneous / Homogeen Reactants and products are in the same phase. Reaktanse en produkte is in dieselfde fase. (2) 6.2 CALCULATIONS USING NUMBER OF MOLES: BEREKENINGE WAT GETAL MOL GEBRUIK: Mark allocation/Puntetoekenning:

n(CCℓ4) at equilibrium = 0,9 mol / n(CCℓ4) by ewewig = 0,9 mol. Ratio/Verhouding: CS2 : Cℓ2 : S2Cℓ2 : CCℓ4 = 0,9 : 2,7 : 0,9 : 0,9 Equilibrium n(CS2) & n(Cℓ2): initial – change

Ewewig n(CS2) & n(Cℓ2): aanvanklik – verandering Equilibrium: n(S2Cℓ2) = initial + change

Ewewig: n(S2Cℓ2) = aanvanklik + verandering Divide ALL equilibrium number of moles by 5 dm3.

Deel ALLE ewewigs getal mol deur deur 5 dm3. Correct Kc expression (formulae in square brackets).

Korrekte Kc-uitdrukking (formules in vierkanthakies) Substitution of equilibrium concentrations into Kc expression.

Vervanging van ewewigskonsentrasies in Kc-uitdrukking. Substitution of Kc value. / Vervanging van Kc-waarde. Final answer/Finale antwoord: 4,92

Kc = 3

22

422

]C][CS[

]CC][CS[

=

3)65,0)(15,0(

)45,0)(45,0( = 4,92

(8) 6.3 6.3.1 Decreases / Verlaag (1) 6.3.2 Remains the same / Bly dieselfde (1)

CS2 Cℓ2 S2Cℓ2 CCℓ4

Initial mol Aanvanklike mol

1,2 4 0 0

Change in mol Verandering in mol

0,9 2,7 0,9 0,9

Mole at equilibrium Mol by ewewig 0,3 1,3 0,9

154

6,138 = 0,9

Equilibrium concentration Ewewigskonsentrasie (mol·dm-3)

0,15 0,65 0,45 0,45

Ratio/ Verhouding

Divide by 5/Gedeel deur 5

No Kc expression, correct substitution/

Geen Kc-uitdrukking, korrekte substitusie: Max./Maks. 8

7



6.4 Reactants were removed./Reaktanse is verwyder. OR/OF CS2 and/or Cℓ2 were removed./ CS2 en/of Cℓ2 is verwyder. (1) 6.5 Incease / Verhoog (1) 6.6

With an increase in temperature, the rates of both the forward and reverse reactions increase. Met 'n verhoging in temperatuur verhoog die tempos van beide die voor- en terugwaartse reaksies.

The rate of the reverse endothermic reaction increases more than that of the forward reaction. Die tempo van die terugwaartse endotermiese reaksie verhoog meer as dié van die voorwaarste reaksie.

OR/OF The rate of the forward exothermic reaction increases less than that of reverse reaction. Die tempo van die voorwaarste eksotermiese reaksie verhoog minder as dié van die terugwaartse reaksie.

The rate of the forward reaction then increases gradually due to the increase in concentration of reactants. / Die tempo van die voorwaartse reaksie verhoog dan stelselmatig as gevolg van die verhoging in konsentrasie van reaktanse.

The rate of the reverse reaction then decreases gradually due to the decrease in concentration of products. / Die tempo van die terugwaartse reaksie verlaag dan stelselmatig as gevolg van die verlaging in konsentrasie van produkte.

Equilibrium is reached after 22 minutes / the rate of forward and reverse reactions are equal after 22 minutes. Ewewig word na 22 minute bereik / die tempo van voor- en terugwaartse reaksies is gelyk na 22 minute. (5)

[19]




Reactants Products Balancing

Reaktanse Produkte Balansering

Ignore/Ignoreer → and phases / en fases Marking rule 3.10/Nasienreël 3.10

QUESTION 7 7.1 7.1.1 Diprotic / Diproties (1)

7.1.2 HSO

4 (1)

7.1.3 Sulphate ion / Sulfaatioon (1)

7.2 7.2.1 pH = -log[H3O+] 0 = -log[H3O+] [H3O+] = 100 = 1 mol·dm-3 [HCℓ] = 1 mol·dm-3

c = V

n

1 = 31050

n

n = 5 x 10-2 mol (0,05 mol) (5)

7.2.2 23CO + H2O ⇌ HCO

3 + OH- Bal.

(3) 7.2.3 Burette / Buret (1)



7.2.4 POSITIVE MARKING FROM QUESTION 7.2.1. POSITIEWE NASIEN VAN VRAAG 7.2.1.

n(NaOH) = cbVb = (0,4)(30 x 10-3) = 0,012 mol

1

1

n

n

b

a

n(HCℓ in excess/in oormaat) = n(NaOH) = 0,012 mol n(HCℓ reacted with/gereageer met Na2CO3): n(HCℓ) = n(initial) – n(reacted with NaOH) = 0,05 – 0,012 = 0,038 mol n(Na2CO3 reacted):

ab

b

a n2

1n

1

2

n

n =

2

1(0,038) = 0,019 mol

M

mn

0,019 = 106

m

m = 2,01 g (6) [18]


Substitute cNaOH and VNaOH / Vervang cNaOH en VNaOH

n(HCℓ) = n(NaOH)

Answer from/Antwoord van Q7.2.1 – n(HCℓ)

n(Na2CO3) = ½n(HCℓ)

Substitute 106 and n(Na2CO3) into M

mn .

Substitueer 106 en n(Na2CO3) in M

mn

Final answer / Finale antwoord: 2,01 g



Eocell = Eo

cathode – Eoanode

1,53 = - 0,13 - Eoanode

Eoanode = 1,66 V

X = Aℓ

Notes/Aantekeninge

Accept any other correct formula from the data sheet. Aanvaar enige ander korrekte formule vanaf gegewensblad.

Any other formula using unconventional abbreviations, e.g. E°cell =

E°OA - E°RA followed by correct substitutions: 5

4.Max

Enige ander formule wat onkonvensionele afkortings gebruik bv.

E°sel = E°OM - E°RM gevolg deur korrekte vervangings: 54Maks.


2H2O + 2e- ⇌ H2 + 2OH- (2

1 ) 2H2O + 2e- ← H2 + 2OH- (2

2 )

H2 + 2OH- ⇌ 2H2O + 2e-

20 H2 + 2OH-

2H2O + 2e- (2

0 )

QUESTION 8/VRAAG 8 8.1 X (1) 8.2 (5) 8.3 8.3.1 Higher than / Hoër as Ag+ is a stronger oxidising agent than Pb2+. Ag+ is 'n sterker oksideermiddel as Pb2+. (2) 8.3.2 Aℓ(s) | Aℓ3+ (1 mol·dm-3) || Ag+ (1 mol·dm-3) | Ag(s) OR/OF Aℓ(s) | Aℓ3+ (aq) || Ag+ (aq) | Ag(s) OR/OF Aℓ | Aℓ3+ || Ag+ | Ag (3) [12] QUESTION 9/VRAAG 9 9.1 Electrolytic (cell) / Elektrolitiese (sel) (1) 9.2 9.2.1 P (1) 9.2.2 2H2O + 2e- H2 + 2OH-

(2)

ACCEPT/AANVAAR:

X | X3+ || Ag+ | Ag


Copyright Reserved/Kopiereg voorbehou


Reactants Products Balancing Reaktanse Produkte Balansering

Ignore/Ignoreer ⇌ and phases / en fases Marking rule 3.10/Nasienreël 3.10


Reactants Products Balancing Reaktanse Produkte Balansering

Ignore/Ignoreer ⇌ and phases / en fases Marking rule 3.10/Nasienreël 3.10

9.2.3 Q to/na P (1)

9.2.4 Water (1)

9.3 2H2O + 2Cℓ- → H2 + 2OH + Cℓ2 Bal.

OR/OF 2H2O + 2NaCℓ

→ H2 + 2NaOH + Cℓ2 Bal. (3)

[9]

QUESTION 10/VRAAG 10

10.1 Percentage of fertiliser (N, P and K) present in the fertiliser. Die persentasie kunsmis (N, P en K) teenwoordig in die kunsmis. (1)

10.2 10.1.1 A (1)

10.2.2 C (1)

10.2.3 C (1)

10.3

10.3.1 %N = 286

3 = 14% (2)

10.3.2 (3) 10.4 NH3 + H2SO4 → (NH4)2SO4 Bal.

(3) [12]

GRAND TOTAL/GROOTTOTAAL: 150

OPTION 1/OPSIE 1 22% of 20 kg = 4,4 kg

9

4 x 4,4 = 1,96 kg

OPTION 2/OPSIE 2

9

4 x 22 = 9,78%

9,78% of 20 kg = 1,96 kg

OPTION 3/OPSIE 3 22% of 20 kg = 4,4 kg 44,44% of 4,4 = 1,96 kg

GRADE/GRAAD 12 SEPTEMBER 2014 - Doc Scientia physical science… · GRADE/GRAAD 12 SEPTEMBER 2014...

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