MAKTAB SULTAN ABU BAKAR

UJIAN PENILAIAN PRA-PENTAKSIRAN SEM 3 2014

SUBJECT : CHEMISTRY

Section A

[15 marks]

1 A 6 D 11 C

2 D 7 A 12 D

3 C 8 D 13 D

4 B 9 C 14 C

5 C 10 B 15 A

16. a) Each correct structure = 1 x 4

i.

ii.

iii.

iv.

b) Geometrical isomer present @ each C in C=C is

surrounded by 2 different atoms / group of atoms [1]

cis - isomer trans - isomer

(Structures [1] label cis trans [1] )

17. correct type of reaction [1] x 4 reagent [1] x 4

Type of reaction Reagent

I Free radical substitution Br2 under UV / hv

ii. Elimination Alumina @ conc. H2SO4

under heating

iii. Oxidation Cold, dilute KMnO4/H

+

@ OH-

iv. Nucleophilic substitution Ethanolic conc. NH3

under reflux

18. a) i. Calculate mole [1] ; stating empirical formula [1]

Element Carbon, C Hydrogen, H

Mass 92.3 7.7

Mole 92.3/12 = 7.7 7.7 / 1 = 7.7

Mol ratio 7.7 / 7.7 = 1 7.7 / 7.7 = 1

Empirical formula = CH

ii. (CH)n = 104 ; (13) x n = 104 ; n = 8

Molecular formula = C8H8 [1] Structure [1]

iii. Major [1] Minor [1] (no label only 1)

iv. to produce polystyrene / container.

18 .b) Each structure = 1 m x 8

A : CH3CH2Cl / AlCl3 B : Cl2 ; uv

C : D : I2 in NaOH

E : F : CH3COCl / AlCl3

G : CH3Cl / AlCl3 H :

19. a) m1 : Mechanism : SN2 [1]

m2 : Nucleophile : CN-. [1]

m3 : Structure : CH3CH2CH2CH2Cl [1]

m4 : and CH(CH3)2CH2Cl [1]

m5 - m8 refer to diagram below [4]

b) i. rate = k[CH3CH2CH2CH2Cl][CN

-] / CN

- is first order [1]

- increasing CN- will increase the rate of reaction [1]

ii. - rate of reaction increased [1]

Since C-Br bond length is longer / bond strength weaker [1]

c) m1 : 2-chloro-2-methylpropane [1] m2 : [1]

m3 : steric hindrance [1]

20.a) m1 : Acidity decrease according to order [1]

m2 : cyclohexane is electron-donating / positive inductive [1]

m3 : caused alkoxide more readily to accept proton @ cause

equilibrium shift to left [1]

m4 : benzene is electron withdrawring / negative inductive [1]

m5 : caused phenol more readily to donate proton @ caused

equilibrium shift to right [1]

m6 : NO2 gives negative inductive / electron withdrawing /

stabilised phenoxide ion formed [1]

20. b) Alternative 1 : Reagent : acidified KMnO4 / H

+ [1]

Observation : purple colour decolourised by cyclohexanol but

not by phenol [1]

Equation : [1]

Alternative 2 : Reagent : bromine water [1]

Observation : brown colour decolourised and white precipitate

is formed when added to phenol [1]

Equation : bromination of phenol [1]

20 c) m1 : Saytzeff rule : in elimination of H-X or H2O, H is

preferable to eliminate from neighbouring C with less H [1]

m2 : reagent : alumina / conc. H2O under heating [1]

m3 : Structure of 2,3-dimethylpentan-3-ol [1]

m4 ; m5 ; m6 - 3 products of dehydration [3]