PPA 1

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Unit 2 PPA 1 DISTINGUISHING TESTS FOR ALDEHYDES
AND KETONES
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DISTINGUISHING TESTS FOR ALDEHYDES AND KETONES
(Unit 2 PPA 1)
The aim of the experiment is to find out how we
can use chemical tests to distinguish between
aldehydes and ketones.
(1) What functional group do both aldehydes and
ketones contain?
(1) The carbonyl group.
(2) Draw extended structural formulae for the
isomers propanal and propaone.
(3) (a) Describe the change you would see when
propanal and propanone were reacted
with an acidified solution of potassium
dichromate. (b) Use the data booklet for
write the ion-electron equation for the
reduction of dichromate ions to chromium(III)
ions.
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(4) (a) Describe the change you would see when
propanal and propanone were reacted
with Fehlings solution. (b) Use the data
booklet for write the ion-electron equation for
the reduction of the copper(II) ions to
copper(I) ions.
(5) (a) Describe the change you would see when
propanal and propanone were reacted
with Tollens reagent (ammoniacal silver(I)
nitrate) (b) Use the data booklet for write
the ion-electron equation for the
reduction of the silverII) ions to silver atoms.
6) Explain why there is a reaction with the
propanal but no reaction with the propanone
with these reagents.
(6) The propanal can be oxidised to
propanoic acid. The propanone cannot be
oxidised.