240967952 Chemistry STPM Sem 3 MSAB Pre Trial Question

UJIAN PENILAIAN PRA-PENTAKSIRAN MSAB

SEMESTER 3 /2014

Section A

[ 15 marks ]

Answer all questions in this section. Write your answer on the spaces provided in page 5 1.

Naphthalene is an active component in mothballs. Its structural formula is shown below. How many hydrogen atoms are there in the molecule? A

2.

8

B

10

C

11

12

What happens when one mole of ethane is mixed in the dark at room temperature with six moles of chlorine? A C

3.

CCl3CCl3 and HCl are formed. CH3CCl3 and HCl are formed.

B D

CH3CH2Cl and HCl are formed. There is no reaction.

Which one of the following is a propagation step in the reaction between methane and chlorine when they are irradiated with light? A. C.

4.

H• + Cl2 → HCl + Cl• CH4 + Cl• → •CH3 + HCl

B. D.

CH4 + Cl+ → CH3+ + HCl CH4 + Cl2 → •CH3 + •Cl + HCl

Which of the following statements is not caused by the delocalisation of pi electrons in benzene? A. B. C. D.

5.

The C-C bond lengths in benzene are identical. Each carbon atom in benzene undergoes sp2 hybridisation. Benzene tends to undergo substitution rather than addition reactions. The enthalpy of hydrogenation of benzene is higher than that of cyclohexene. A hydrocarbon X contains 85.7% carbon and 14.3% of hydrogen by mass. X reacts with hydrogen in the presence of nickel catalyst. The structural formula of X could be.

A.

CH3CH2CH2CH2CH2CH3

B.

C. 6.

D

CH3CH=CHCH2CH2CH3

D.

Which of the following statements about the two alkenes CH3CH2CH=CH2 and CH3CH=CHCH3 are incorrect? I. Both exhibits cis - trans isomerism. II. Both may be polymerised. III. Both reacts with bromine to give 1,4-dibromobutane. IV. Both reacts with hydrogen to form butane A. C.

I and II only II and III only correct

B.

I and III only D. II and IV only correct

Trichloroethene, CHCl=CCl2, is widely used as a dry-cleaning agent. With which of the following does trichloroethene react to give a chiral product?

7. A.

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Br2

B.

H2

C.

HCl

D.

NaOH

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8.

SEMESTER 3 /2014

Which of the following reactions is an example of electrophilic addition? I. II. III. IV.

CH2=CH2 + H2SO4 → CH3CH2OSO3H CH2=CH2 + Br2 + H2O → CH2BrCH2Br + CH2BrCH2OH C6H6 + HNO3 → C6H5NO2 + H2O C6H6 + 3 Cl2 → C6H6Cl6

A. C.

I only correct I, II and III only correct

9.

B. D.

I and II only correct I, II and IV only correct

Which of following statements about the reaction below could be correct? C6H6 A. B. C. D.

10.

+

HNO3

. H 2SO 4 conc  →

C6H5NO2 + H2O

The reaction is carried out at temperature between 0°C to 10°C. The reaction is a nucleophilic substitution reaction. The nitronium ion attacks benzene ring at the initial stage of reaction. The concentrated sulphuric acid acts as a strong oxidising agent in the reaction. Which reagent and conditions are used to bring about the reaction shown?

A. B. C. D. 11.

Cl2 in the dark Cl2 with AlCl3 Cl2 with ultraviolet light concentrated HCl catalysed by ZnCl2 heated under reflux An amine compound is formed according to the following reaction.

What are the reagents required in step I and step II of the above reactions? Step I Ammonia gas Ammonia gas Potassium cyanide Aqueous Ammonia gas

A B C D 12.

Step II Hydrogen gas Hydrogen cyanide Lithium tetrahydridoaluminate Sodium hydroxide in ethanol

An amine is prepared in the following reaction. C2H5I + 2NH3 →

C2H5NH2 + NH4I

What is the type of reaction take place? A. C.

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Electrophilic addition Nucleophilic addition

B. D.

Electrophilic substitution Nucleophilic substitution

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13.

SEMESTER 3 /2014

It is estimated that for every chlorine atom formed from a fluorohaloalkane in the stratosphere, one hundred thousand ozone atoms may be destroyed. Which of the following statements provides an explanation for this? A. B. C. D.

14.

They achieve high activation energy by absorbing ultraviolet light. They eliminate oxygen from ozone - oxygen equilibrium. They initiate ionisation of oxygen molecule. They are regenerated in a chain reaction with ozone. The scheme below shows the formation of compound Z from propan-2-ol.

Which of the following compounds could be X, Y, and Z? X

Y

Z

O

15.

A

PCl5

B

PCl5

C

SOCl2

D

Cl2

CH 3CH2CH

When aqueous bromine is added to an organic compound Y, the colour of bromine is discharged. To which classes of compound could Y belong? I. III.

Alkene Haloalkane

II. IV.

Phenol Aliphatic alcohol

A. C.

I and II only correct II and III only correct

B. D.

I and III only correct II and IV only correct

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UJIAN PENILAIAN PRA-PENTAKSIRAN MSAB

SEMESTER 3 /2014

MAKTAB SULTAN ABU BAKAR UJIAN PENILAIAN PRA-PENTAKSIRAN SEM 3 2014 SUBJECT : CHEMISTRY Name : ____________________________________

Tingkatan : UPPER 6 ____________

Section A [15 marks] 1

6

11

2

7

12

3

8

13

4

9

14

5

10

15

Section B

[ 15 marks ]

Answer all questions in this section

, is a colourless liquid which is used as a solvent.

16.

Crotyl alcohol,

(a)

In the boxes below, write the structural formula of the organic compound(s) formed when crotyl alcohol is reacted separately with each reagent under suitable conditions. [4 x 1 mark]

(b)

i.

Hydrogen gas catalysed by platinum

ii.

Phosphorous pentachloride

iii.

Bromine water

iv.

hot concentrated acidified potassium manganate (VII)

Explain the stereoisomer present in crotyl alcohol and draw the isomers stated.

[3 marks]

…………………………………………………………………………………………………………... ………………………………………………………………………………………………………….. Isomers present :

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17.

SEMESTER 3 /2014

Organic chemistry is the chemistry of carbon compounds. The types of organic reactions that you have studied are listed below. Addition

Elimination

Hydrolysis

Oxidation

Reduction

Substitution

Addition and substitution reactions are further described as follows. Electrophilic

Nucleophilic

Free radical

Complete the table below. Fill in the central column by using only the types of reaction given in the lists above. Use both lists when appropriate. In the right hand column give the name(s) or formula(e) of the reagent(s) you would use to carry out the reaction given. [4 x 2 marks] Organic reaction

type of reaction

Reagent and Condition

CH3CH2CH2CH3
CH3CH2CHBrCH3 CH3CH(OH)CH3
CH3CH=CH2 CH3CH=CH2
CH3CH(OH)CH2OH CH3CH2Cl
CH3CH2NH2

Section C

[30 marks]

Answer any two questions in this Section 18. (a) i. ii. iii.

iv. (b)

A liquid hydrocarbon, M, has the following composition by mass: C, 92.3%; H, 7.7%. Calculate the empirical formula of the hydrocarbon. [2 marks] Given the molecular mass of M is 104, deduce the molecular formula and molecular structure of M [2 marks] When M react with hydrogen chloride gas, it gives two products which follow Markovnikoff's rules. Draw the structures of the two products and label according to major and minor products formed [2 marks] State one use of M in industries [1 mark] The following reaction scheme shows the formation of different

State the reagents or compound formed from A to H in the above reaction scheme.

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[8 marks]

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UJIAN PENILAIAN PRA-PENTAKSIRAN MSAB

19.

SEMESTER 3 /2014

The reaction - energy profile for the reaction between haloalkane, P, with molecular formula C4H9Cl and a solution of ethanolic potassium potassium cyanide below. Energy / kJ

Reactants

Products Reaction coordination

(a)

From the reaction - energy profile, name and describe the mechanism of the reaction take place , and suggest the possible molecular structure that undergoes the mechanism stated [8 marks]

(b)

Explain the effects toward the rate of reaction for the following changes i. ii.

(c)

the concentration of potassium cyanide increased haloalkane P is replaced with another haloalkane with the formula C3H7Br

[2 marks] [2 marks]

Another isomer of is not favourable to the mechanism proposed in (a). Draw and name the structure of the isomer described to explain why it does not favour such mechanism [3 marks]

20. (a)

The table below list the pKa value for three hydroxyl compound in aqueous solution at 298 K Name of compound

Formula

pKa

Cyclohexanol

18

Phenol

10

4-nitrophenol

9.2

i.

Arrange the three compound above in the order of decreasing acidity and explain your answer [6 marks]

ii.

State a chemical test used to distinguish between cyclohexanol and phenol

(b)

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[3 marks]

2,3-dimethylpentan-3-ol dehydrated according to Saytzeff's rule using suitable reagent and condition. By drawing the structure of the products formed, explain how the yield of the products varies according to the rules [6 marks]

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