Organic Chemistry Click to start

Question 1 How many structural isomers are possible with the molecular formula C 6 H 14 ?

Wrong Answer!

Question 2 Which formulas represent butane or its isomer? I.CH 3 (CH 2 ) 2 CH 3 II.CH 3 CH (CH 3 )CH 3 III.(CH 3 ) 3 CH I, II and III I and III only II and III only I and II only

Wrong Answer! All structures are valid and have the molecular formula C 4 H 10.

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 Alkenes Alkanes

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 Soot Carbon 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? CH 3 CHO CH 3 COOCH 3 CH 3 COOCH 2 CH 3 CH 3 CH 2 COOCH 3

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

Question 6 Which compound is a member of the aldehyde homologous series? CH 3 CH 2 COCH 3 CH 3 CH 2 CHO CH 3 CH 2 COOH CH 3 CH 2 CH 2 COH

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 alcohol a secondary alcohol

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

Question 8 Which of the following descriptions can be correctly applied to the homologous series of alkanes? I.Members of the series have the general formula C n H 2n+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 only I 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? CH 3 CH 2 COOH C 2 H 5 OC 2 H 5 HCOOCH 3 C 3 H 7 CHO

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 water Test 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 CH 3 CH 2 CH 2 COOCH 3 ? butyl methanoate methyl butanoate pentanone methyl 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.

C 13 H 28 Question 12 A gaseous hydrocarbon, X, decolorizes aqueous bromine.Which one of the following molecular formulas could be X? C2H4C2H4 C 6 H 14 C 10 H 20

Wrong Answer! C 6 H 14 and C 13 H 28 are both alkanes, C 2 H 4 and C 10 H 20 are both alkenes, but only C 2 H 4 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: Cl 2 (g)  2 (g)

Question 14 What is the IUPAC name for (CH 3 ) 2 C(OH) CH 2 CH 3 ? pentan-3-ol 2-methylbutan-2-ol 4-methylbutan-3-ol 3-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 15 How 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, compared to 120 0, 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? CH 4 (g) + O 2 (g)  C(s)+2H 2 O(g) CH 4 (g) + O 2 (g)  CO 2 (g)+2H 2 (g) CH 4 (g) + 2O 2 (g)  CO 2 (g)+2H 2 O(g) 2CH 4 (g) + 3O 2 (g)  2CO (g)+4H 2 O(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, 2 4, 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: CH 3 CH 2 CH 2 F CH 3 CH 2 COOH CH 3 CH 2 CH 2 NH 2 CH 3 CH 2 CH 2 OH

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 III II 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 radicals

Wrong Answer! The bond between the 2 chlorine atoms in Cl 2 is weaker than C-H or C-C bond in CH 4 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 + H 3 C-C = C-CH 3  H 3 C – C – C – CH 3 H H H H

Question 22 The oxidation of propan-2-ol, CH 3 CH(OH)CH 3, by sodium dichromate(VI) leads to the formation of: Propanone, CH 3 COCH 3 Propan-1-ol, CH 3 CH 2 CH 2 OH Propanoic acid, CH 3 CH 2 CO 2 H Propanal, CH 3 CH 2 CHO

Wrong Answer! Oxidation of secondary alcohol forms a ketone.

Congratulations!