AS LEVEL CHEMISTRY

	BASIC CONCEPTS IN ORGANIC CHEMISTRY

ASSESSED HOMEWORK

Answer all questions
Max 47 marks

	
Name		……………………………………………………………..

Mark		……../47	……....%	Grade ………

1.	The table below lists the boiling points of some alkanes.
alkane	number of
carbon atoms	molecular
formula	boiling point /°C	
butane	4	C4H10	0	
pentane	5	C5H12	36	
hexane	6	C6H14	69	
heptane	7	C7H16	99	
octane	8	C8H18		
nonane	9	C9H20	152	
decane	10	C10H22	175	
(i)	Predict the boiling point of octane.
.........................................................................................................................
[1]
(ii)	State and explain the trend in the boiling points of these alkanes.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[2]
[Total 3 marks]

2.	The table below lists the boiling points of some alkanes.
alkane	number of carbon atoms	molecular formula	boiling point / °C	
butane	4	C4H10	0	
pentane	5	C5H12	36	
hexane	6		69	
heptane	7	C7H16	99	
octane	8	C8H18		
nonane	9	C9H20	152	
decane	10	C10H22	175	
(a)	What is the molecular formula of hexane?......................................................
[1]
(b)	(i)	State the trend in the boiling points of the alkanes.
................................................................................................................
................................................................................................................
[1]
(ii)	Explain the trend in the boiling points of the alkanes.
................................................................................................................
................................................................................................................
[1]
(iii)	Predict the boiling point of octane.	.................. °C
[1]
[Total 4 marks]

3.	Predict the molecular formula of an alkane with 13 carbon atoms.
..................................................................................................................................
[Total 1 mark]

4.	Alkenes are unsaturated hydrocarbons. The structures of but-1-ene and methylpropene are shown below.

(i)	What is meant by the terms unsaturated and hydrocarbon?
unsaturated .....................................................................................................
hydrocarbon ....................................................................................................
[2]
(ii)	Suggest values for the bond angle a in but-1-ene and the bond angle b in methylpropene.
angle a	.............................	angle b	.............................
[2]
(iii)	Explain, with the aid of a sketch, how p-orbitals are involved in the formation of the C==C double bond.
.........................................................................................................................
.........................................................................................................................
[2]
[Total 6 marks]

5.	Cylcohexane and cyclohexene are both cyclic hydrocarbons.

cyclohexane	 cyclohexene
(i)	What is the molecular formula of cyclohexene? .............................................
[1]
(ii)	What is the empirical formula of cyclohexene? ..............................................
[1]
(iii)	Calculate the percentage, by mass, of carbon in cyclohexene. Give your answer to two significant figures.

answer ...............................................
[2]
[Total 4 marks]

6.	There are several cycloalkanes that are structural isomers of C5H10.
(i)	Complete the boxes by drawing two other structural isomers of C5H10 that are also cycloalkanes.
				
Isomer L		ethylcyclopropane		
[2]
(ii)	Name isomer L drawn in (i).
.........................................................................................................................
[1]
(iii)	Draw the skeletal formula of isomer L.
[1]
[Total 4 marks]

7.	(a)	Many organic molecules show structural isomerism. State what is meant by the term structural isomerism.
.........................................................................................................................
.........................................................................................................................
[2]
(b)	Isomers 1, 2 and 3, shown below, are unsaturated structural isomers of C5H10.

		
(i)	Complete the boxes by drawing two other unsaturated structural isomers of C5H10.
[2]
(ii)	Name isomer 3.
................................................................................................................
[1]
(iii)	Draw the skeletal formula of isomer 2.

[1]
[Total 6 marks]

8.	In this question, one mark is available for the quality of use and organisation of scientific terms.
·	Describe, with the aid of a suitable diagram, the formation of the p-bond in propene.
·	State the shape, and an approximate value for the bond angles, around each carbon atom in propene.
·	Describe, with the aid of a suitable example, why some alkenes show
cis-trans isomerism.

[9]
Quality of Written Communication [1]
[Total 10 marks]

9.	In this question, one mark is available for the quality of use and organisation of scientific terms.
Name and give examples of the types of isomerism in compounds with formula C4H8. Explain how each type of isomerism arises.

[8]
Quality of Written Communication [1]
[Total 9 marks]