Last saved by: Luke

AS LEVEL CHEMISTRY

2.1.1 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 | C_4H_10 | 0
pentane | 5 | C_5H_12 | 36
hexane | 6 | C_6H_14 | 69
heptane | 7 | C_7H_16 | 99
octane | 8 | C_8H_18 |
nonane | 9 | C_9H_20 | 152
decane | 10 | C_10H_22 | 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 | C_4H_10 | 0
pentane | 5 | C_5H_12 | 36
hexane | 6 | | 69
heptane | 7 | C_7H_16 | 99
octane | 8 | C_8H_18 |
nonane | 9 | C_9H_20 | 152
decane | 10 | C_10H_22 | 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 C_5H_10.
(i)	Complete the boxes by drawing two other structural isomers of C_5H_10 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 C_5H_10.
(i)	Complete the boxes by drawing two other unsaturated structural isomers of C_5H_10.
[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 π-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 C_4H_8. Explain how each type of isomerism arises.

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

Paddington Academy