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SPECIMEN H
GENERAL CERTIFICATE OF SECONDARY EDUCATION
TWENTY FIRST CENTURY SCIENCE A173/02
CHEMISTRY A
Unit A173: Module C7 (Higher Tier)


Candidates answer on the question paper
A calculator may be used for this paper

OCR Supplied Materials:
None Duration: 1 hour

Other Materials Required:
Pencil
Ruler (cm/mm)


Candidate Candidate
Forename…

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2

Answer all the questions.
1 Methanoic acid, HCOOH, is a carboxylic acid that is present in bee stings.
(a) What is the formula of the functional group that is responsible for the characteristic
properties of carboxylic acids?


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(b) Methanoic acid is used to remove the limescale in…

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(iii) Methanoic acid is a weak acid and hydrochloric acid is a strong acid.
Describe a reaction, other than with carbonates, that shows that methanoic acid is an
acid.
Compare this with a similar reaction of hydrochloric acid to demonstrate why one is a
weak acid and the other…

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2 Sunflower oil is an example of a vegetable oil. The oil comes from the seeds of the sunflower
plant.
The chemicals in the oil are esters.




(a) When an ester is hydrolysed it forms an alcohol and a carboxylic acid.
This reaction is the reverse of the reaction…

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(b) An ester can be made by reacting an alcohol with a carboxylic acid. The technique used
involves four stages: reflux, distillation, purification and drying.
In the reflux stage, the alcohol and ester are heated with a little concentrated
sulfuric acid in a flask with a condenser attached in…

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3 A technician analyses a mixture of hydrocarbons using gas chromatography.
She first calibrates the equipment using standard hydrocarbons. The retention times of these
hydrocarbons are shown in the table.

hydrocarbon formula retention time
in minutes
methane CH 4 1.7
ethane C2H6 2.2
propane C3H8 3.5
butane C 4…

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(b) During gas chromatography, each component of a mixture is involved in a dynamic
equilibrium.
Explain how this separates the components in a mixture.

The quality of written communication will be assessed in your answer to this question.


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[Total: 8]…

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4 A company makes indigestion tablets that contain the active ingredient magnesium hydroxide.
This neutralises excess stomach acid to relieve the symptoms of acid indigestion. The tablets
also contain starch.
A chemist analyses samples from each batch of indigestion tablets that the company makes.
He uses quantitative analysis to…

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(iii) Use the neutralisation equation below to work out the mass of magnesium hydroxide
that reacts with this mass of hydrochloric acid. This is the average mass of magnesium
hydroxide in each tablet.
The relative formula mass of hydrochloric acid, HCl, is 36.5.


Mg(OH) 2 + 2HCl MgCl 2…

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(b) Use the table of titration results to assess the degree of uncertainty in your calculated value
of the mass of magnesium hydroxide in each tablet.
Explain your answer.


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[Total: 8]




© OCR 2011 SPECIMEN

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