Organic Chemistry

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Question 1

How many structural isomers are possible with the molecular formula C6H14?

4 6

75

Wrong Answer!

Question 2

Which formulas represent butane or its isomer?

I. CH3 (CH2)2CH3

II.CH3CH (CH3)CH3

III.(CH3)3CH

I, II and III I and III only

II and III onlyI and II only

Wrong Answer!All structures are valid and have the molecular formula C4H10.

Question 3

Blur Professor Sim intends to create PVC through polymerisation but does not know which monomer to use. Which homogolous series would be appropriate?

Alcohols Carboxylic acids

AlkenesAlkanes

Wrong Answer!Alkenes and substituted alkenes readily undergo addition reactions by breaking one of the double bonds. They can be joined together to form polymers.

Question 4

Excess ethane was burnt in a closed system. Which of the following is not a possible product?

Water Carbon monoxide

SootCarbon dioxide

Wrong Answer!Incomplete combustion of hydrocarbon produces carbon monoxide, water and soot.

Question 5

What is the organic product of the reaction between ethanol and ethanoic acid in the presence of concentrated sulfuric acid?

CH3CHO CH3COOCH3

CH3COOCH2CH3CH3CH2COOCH3

Wrong Answer!The product is an ester, ethyl ethanoate.

Question 6

Which compound is a member of the aldehyde homologous series?

CH3CH2COCH3 CH3CH2CHO

CH3CH2COOHCH3CH2CH2COH

Wrong Answer!Aldehydes contain the –CHO functional group.

Question 7

What type of alcohol is 2-methylpropan-2-ol?

an unsaturated alcohol

a tertiary alcohol

a primary alcohola secondary alcohol

Wrong Answer!It is a tertiary alcohol, C(CH3)3 or CH3C(CH3)2-OH

Question 8Which of the following descriptions can be correctly applied

to the homologous series of alkanes?

I. Members of the series have the general formula CnH2n+2

II. Members of the series have similar chemical properties.

III.Members of the series are isomers of each other.

I only II only

I and III onlyI and II only

Wrong Answer!The members of a homologous series are not isomers of each other, other statements are correct.

Question 9

Which compound is an ester?

CH3CH2COOH C2H5OC2H5

HCOOCH3C3H7CHO

Wrong Answer!It contains an ester linkage: -COO-

Question 10

Which one of the following is the best method of distinguishing between an alkane and alkene?

Test with universal indicator

Burn the gases in excess oxygen

Add bromine waterTest their solubility in water

Wrong Answer!Alkenes rapidly react with bromine water via addition reaction.

Question 11

What is the name of the compound whose condensed structural formula is CH3CH2CH2COOCH3?

butyl methanoate methyl butanoate

pentanonemethyl propanoate

Wrong Answer!The compound is an ester formed from butanoic acid (see first part of the structure) and methanol (see seoncd part of the structure); therefore it is methyl butanoate.

C13H28

Question 12

A gaseous hydrocarbon, X, decolorizes aqueous bromine.Which one of the following molecular formulas could be X?

C2H4 C6H14

C10H20

Wrong Answer!C6H14 and C13H28 are both alkanes, C2H4 and C10H20 are both alkenes, but only C2H4 is a gas at room temperature.

Question 13

What is the function of sunlight during the reaction between chlorine and methane?

To dissociate the chlorine molecules into atoms.

To dissociate the chlorine molecules into ions

To break the C-H bonds in the methane molecule.

To increase the temperature of the mixture.

Wrong Answer!Light is a form of energy and is absorbed by chlorine molecules to dissociate the covalanet bond between the two chloribe atoms. Homolytic fission occurs:

Cl2(g) 2 (g) Cl

Question 14

What is the IUPAC name for (CH3)2C(OH) CH2CH3?

pentan-3-ol 2-methylbutan-2-ol

4-methylbutan-3-ol3-methylbutan-3-ol

Wrong Answer!There are 4 carbon atoms in the longest unbranched chain. There is a methyl group and an –OH group on the second carbon atom.

Question 15How do the bond angles and bond lengths in ethane and

ethene compare?

H-C-H bond C-C bond

angle in ethane length in ethane

larger longer

smaller longer

larger shorter

smaller shorter

Wrong Answer!The bond angle in ethane is smaller, 109.50 compared to 1200 , bond length in ethane is longer as the bond is just a single C-C bond, whereas there is a C=C bond in ethene.

Question 16

Which equation represents the combustion of methane in excess oxygen?

CH4(g) + O2(g) C(s)+2H2O(g)

CH4(g) + O2(g) CO2 (g)+2H2(g)

CH4(g) + 2O2(g) CO2 (g)+2H2O(g)

2CH4(g) + 3O2(g) 2CO (g)+4H2O(g)

Wrong Answer!Carbon dioxide and water are formed by complete combustion of a hydrocarbon.

Question 17

When the compounds below are listed in order of decreasing boiling point (highest to lowest) what is the correct order?

1. ethane 2. chloroethane

3. ethanol 4. ethanoic acid

2, 1, 3, 4 4, 3, 2, 1

3, 4, 1, 24, 3, 1, 2

Wrong Answer!Ethanoic acid and ethanol form stronger hydrogen bond, chloroethane and ethane molecules are bonded by weak van der Waals forces.

Stronger bonds -> Higher boiling point since greater amount of energy is needed to break the bonds.

The order of bond stength is

Ethanoic acid > ethanol > chloroethane > ethane

Hydrogen bonds ------------------------van der Waals forces

Question 18

The compound which is expected to have the lowest boiling point at a pressure of one atmosphere is:

CH3CH2CH2F CH3CH2COOH

CH3CH2CH2NH2CH3CH2CH2OH

Wrong Answer!The molecules will only have van der Waals’ forces acting between them, other examples have the capbility of hydrogen bonding between the molecules.

Question 19

Which products can be potentially obtained from crude oil and are economically important?

I. Plastics

II. Margarine

III.Motor fuel

I and II only I and III only

I, II and IIIII and III only

Wrong Answer!

Question 20

Which statement is correct about the reaction between methane and chlorine?

It involves heterolytic fission and radicals

It involves heterolytic fission and ions

It involves homolytic fission and ions

It involves homolytic fission and radicalsCl

Cl

Cl

Cl

Wrong Answer!The bond between the 2 chlorine atoms in Cl2 is weaker than C-H or C-C bond in CH4 and can break homolytically in the presence of UV to form 2 free Cl radicals.

1-chlorobutane

Question 21

Which product is formed when hydrogen chloride is added to but-2-ene?

2-chlorobutane 2,3-dichlorobutane

1,2-dichlorobutane

Wrong Answer! Cl H

HCl + H3C-C = C-CH3 H3C – C – C – CH3

H H H H

Question 22

The oxidation of propan-2-ol, CH3CH(OH)CH3, by sodium dichromate(VI) leads to the formation of:

Propanone, CH3COCH3

Propan-1-ol, CH3CH2

CH2 OH

Propanoic acid, CH3CH2 CO2H

Propanal, CH3CH2CHO

Wrong Answer!Oxidation of secondary alcohol forms a ketone.

Congratulations!