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
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)
Question
This question is about ethanoic acid, CH3COOH.
(a) Ethanoic acid is manufactured from methanol and carbon monoxide.
\(CH_{3}OH\left ( g \right )+CO\left ( g \right )\rightleftharpoons CH_{3}COOH\left ( g \right )\)
The process is done at 200°C and 30 atmospheres pressure.
The forward reaction is exothermic.
Complete the table using only the words increases, decreases or no change.[4]
(b) How would you show that an aqueous solution of ethanoic acid is an acid without using an indicator or measuring the pH?
State the reagent you would use and give the expected observations. Write a chemical equation for the reaction that you describe.[3]
-
- reagent
- expected observations
- chemical equation
(c) Ethanoic acid is a weak acid.
(i) What is meant by the term acid?[1]
(ii) Why is ethanoic acid described as weak?[1]
(d) Ethanoic acid reacts with methanol to form an ester.
(i) State two conditions required for this reaction.[2]
1
2
(ii) Draw the structure of the ester formed when ethanoic acid reacts with methanol. Show all of the atoms and all of the bonds. Name the ester.[3]
structure
name
(iii) Name an ester which is a structural isomer of the ester in (d)(ii).[1] [Total: 15]
Answer/Explanation
Ans:
4(a)
4(b) M1 Suitable metal e.g. magnesium / any carbonate / any base(1)
M2 suitable observation e.g. insoluble base / insoluble carbonate / metal dissolve or disappear or metal / carbonate bubbles(1)
M3 balanced equation fully correct(1)
4(c)(i) proton donor
4(c)(ii) ionises / dissociates partially or incompletely
4(d)(i) M1 heat(1)
M2 catalyst / concentrated sulfuric acid(1)
4(d)(ii) M1 Correct ester linkage(1)
M1 and M2 whole molecule fully correct(2)
M3 methyl ethanoate (1)
4(d)(iii) ethyl methanoate