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Organic chemistry
10 MDCAT Chemistry questions with answers and explanations.
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What is the IUPAC name of CH3CH2OH?
- 1 Methanol
- 2 Ethanol
- 3 Propanol
- 4 Ethanal
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Correct answer: Ethanol
Two carbons give the stem eth-. The -OH group gives the ending -ol, so the name is ethanol.
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Which functional group is present in carboxylic acids?
- 1 -OH
- 2 -CHO
- 3 -COOH
- 4 -CO-
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Correct answer: -COOH
The carboxyl group, -COOH, is the functional group of carboxylic acids such as ethanoic acid.
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Alkenes mainly undergo which type of reaction?
- 1 Addition
- 2 Substitution only
- 3 Elimination only
- 4 Condensation only
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Correct answer: Addition
The C=C double bond opens up easily, so alkenes react by addition, for example with bromine or hydrogen.
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How many structural isomers does butane (C4H10) have, including itself?
- 1 1
- 2 2
- 3 3
- 4 4
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Correct answer: 2
The two isomers are n-butane and 2-methylpropane (isobutane).
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Complete combustion of a hydrocarbon produces:
- 1 Carbon monoxide and hydrogen
- 2 Carbon dioxide and water
- 3 Carbon and water
- 4 Carbon dioxide and hydrogen
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Correct answer: Carbon dioxide and water
With enough oxygen, all the carbon becomes CO2 and all the hydrogen becomes H2O.
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Benzene mainly undergoes:
- 1 Addition reactions
- 2 Electrophilic substitution
- 3 Nucleophilic addition
- 4 Free radical polymerisation
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Correct answer: Electrophilic substitution
The delocalised ring of electrons is stable. Benzene keeps it and swaps a hydrogen for another group, which is substitution.
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Which reagent is used to test for unsaturation in an organic compound?
- 1 Bromine water
- 2 Lime water
- 3 Benedict's solution
- 4 Iodine in KI
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Correct answer: Bromine water
An unsaturated compound turns orange-brown bromine water colourless because bromine adds across the double bond.
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What is the common name for CH3COCH3?
- 1 Formaldehyde
- 2 Acetone
- 3 Acetic acid
- 4 Methyl alcohol
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Correct answer: Acetone
CH3COCH3 is propanone, commonly called acetone. It is the simplest ketone.
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Gentle oxidation of a primary alcohol, with the product distilled off as it forms, gives:
- 1 A ketone
- 2 An aldehyde
- 3 An alkane
- 4 An ester
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Correct answer: An aldehyde
Primary alcohols oxidise to aldehydes. Further oxidation, if the aldehyde stays in the mixture, gives a carboxylic acid.
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Which of these is an alkyne?
- 1 C2H6
- 2 C2H4
- 3 C2H2
- 4 C6H6
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Correct answer: C2H2
Alkynes have the general formula CnH2n-2 and a carbon-carbon triple bond. C2H2 is ethyne.