Question
The names of four esters are listed.
methyl propanoate
ethyl propanoate
propyl propanoate
butyl propanoate
(a) Esters are a family of organic compounds with similar chemical properties. They can be represented by the formula CnH2nO2.
(i) State the name given to a family of organic compounds with similar chemical properties.[1]
(ii) Explain why members of a family of organic compounds have similar chemical properties.[1]
(iii) State the name given to a formula such as CnH2nO2.[1]
(iv) Determine the value of ‘n’ in butyl propanoate.[1]
(b) All four of the esters in the list are liquids at room temperature.
Name the technique used to separate ethyl propanoate from a mixture of the four esters.[2]
(c) All four esters can be made by reacting different alcohols with the same substance.
(i) Name this substance and draw its structure. Show all of the atoms and all of the bonds.[2]
name
structure
(ii) Name the alcohol used to make methyl propanoate.[1]
(d) Other esters, not in the list, have the same molecular formula as propyl propanoate, but different structures.
(i) State the term used to describe substances with the same molecular formula but different structures.[1]
(ii) Name two esters with the same molecular formula as propyl propanoate.[2]
1
2
(e) Polyesters can be made from the two different molecules shown.
(i) Complete the diagram to show a section of the polyester made from these two molecules. Include all of the atoms and all of the bonds in the linkages.[3]
(ii) Name the type of polymerization that takes place when this polymer forms.[1]
(iii) Name a polyester.[1] [Total: 17]
Answer/Explanation
Ans:
6(a)(i) homologous series
6(a)(ii) Same functional group
6(a)(iii) general (formula)
6(a)(iv) 7
6(b) fractional
distillation
6(c)(i) propanoic acid
structure of propanoic acid
6(c)(ii) methanol
6(d)(i) structural isomers
6(d)(ii) ethyl butanoate
butyl ethanoate
6(e)(i) any correct displayed ester link between any two blocks showing all atoms and all bonds
correct orientation of three displayed inter-block ester links with correct orientation
continuation bonds on polyester
6(e)(ii) condensation
6(e)(iii) terylene
Question
Many organic compounds contain carbon, hydrogen and oxygen only.
(a) An organic compound V has the following composition by mass.
C, 48.65%; H, 8.11%; O, 43.24%
Calculate the empirical formula of compound V.
empirical formula = …………………………
(b) Compound W has the empirical formula CH4O and a relative molecular mass of 32.
Calculate the molecular formula of compound W.
molecular formula = …………………………
(c) Compounds X and Y have the same general formula.
X and Y are both carboxylic acids.
Compound X has the molecular formula \(C_2H_4O_2\).
Compound Y has the molecular formula \(C_4H_8O_2\).
(i) Deduce the general formula of compounds X and Y.
(ii) Draw the structure of compound Y. Show all of the atoms and all of the bonds.
Name compound Y.
name …………………………………………………………………………………………………………………..
(iii) Give the name used to describe a ‘family’ of similar compounds with the same general
formula, similar chemical properties and the same functional group.
(d) Propene is an unsaturated hydrocarbon. The formula of propene is shown.
\(CH_3CH=CH_2\)
(i) State the colour change observed when propene is added to aqueous bromine.
from ……………………………………………………. to ……………………………………………………
(ii) Propene can be produced by cracking long chain alkanes.
Pentadecane, \(C_{15}H_{32}\), is cracked to produce an alkane and propene in a 1:2 molar ratio.
Complete the chemical equation for this reaction.
\(C_{15}H_{32}\) → ………………………………… + …………………………………
(iii) Propene can be converted into poly(propene).
Name the type of polymerisation that occurs when propene is converted into poly(propene).
(iv) Complete the diagram to show a section of poly(propene).
Answer/Explanation
Answer:
(a) 48.65 / 12 8.11 / 1 43.24 / 16 (1)
OR evaluation
4.05 8.11 2.7(0)
divide all by smallest
OR 1.5 : 3 : 1
OR
6 : 3 : 2 (1)
\(C_3H_6O_2\) (1) ALLOW symbols in any order
(b) ( \(M_r\) of \(CH_4O\) = 32)
\(CH_4O\) (1)
(c) (i) \(C_nH_{2n}O_2\)
OR
\(C_nH_{2n+1} COOH\)
(ii) butanoic acid (1)
fully displayed carboxylic acid group (1)
correct structure of butanoic acid showing all atoms and bonds (1)
(iii) homologous series
(d) (i) brown to colourless
(ii) \(C_9H_{20}\) (1)
\(2C_3H_6\) (1)
(iii) addition
(iv) 
any one repeat unit (1)
both repeat units fully correct (1)
Question
Alkenes and carboxylic acids are both families of similar compounds with similar chemical properties.
Alkenes and carboxylic acids have different reactions.
(a) State the term used for a ‘family’ of similar compounds.
(b) State the general formula of alkenes.
(c) The structure of but-2-ene is shown.
(i) But-2-ene reacts with aqueous bromine in an addition reaction.
Describe the colour change seen when but-2-ene is added to aqueous bromine.
from ……………………………………………………. to ……………………………………………………
(ii) State what is meant by the term addition reaction.
(iii) Write the chemical equation for the reaction between but-2-ene and bromine.
(iv) But-2-ene forms a polymer.
Suggest the name of the polymer formed from but-2-ene.
(v) Name and draw a structural isomer of but-2-ene.
Show all of the atoms and all of the bonds.
name …………………………………………………………………………………………………………………..
structure
(d) Butanoic acid, \(CH_3CH_2CH_2COOH\), is a carboxylic acid.
(i) Deduce the empirical formula of butanoic acid.
(ii) Complete the chemical equation for the reaction of butanoic acid and sodium carbonate,
\(Na_2CO_3\).
\(2CH_3CH_2CH_2COOH + Na_2CO_3\) → ……………………………… + …………… + ……………
(iii) Butanoic acid reacts with methanol to form an organic compound and water.
● Name the organic compound formed.
● Draw the structure of the organic compound formed.
Show all of the atoms and all of the bonds.
Answer/Explanation
Answer:
(a) homologous series
(b) \(C_nH_{2n}\)
(c) (i) orange to colourless
(ii) (only) one product is formed
(iii) \(C_4H_8 + Br_2 → C_4H_8Br_2\)
\(C_4H_8Br_2\) (1)
equation fully correct (1)
(iv) (poly) but-2-ene
(v) but-1-ene (1)
structure of but-1-ene
(d) (i) \(C_2H_4O\)
(ii) \(2C_3H_7COOH + Na_2CO_3 → 2C_3H_7COONa + H_2O + CO_2\)
\(C_3H_7COONa\) (1)
equation fully correct (1)
(iii) methyl butanoate (1)
ester link (1)
rest of structure (1)