Which functional group is present in ethanoic acid?
- A.Hydroxyl, -OH
- B.Aldehyde, -CHO
- C.Carboxyl, -COOH
- D.Ketone, -CO-
Correct answer
Explanation
The correct answer is C, the carboxyl group. Ethanoic acid, better known as acetic acid and familiar as vinegar in dilute form, has the formula CH3COOH, and the -COOH group at the end is what makes it acidic, since it releases a hydrogen ion in water and turns blue litmus red. Option A is wrong because the hydroxyl group marks an alcohol such as ethanol, C2H5OH, which is neutral to litmus. Option B is wrong because the aldehyde group ends in -CHO, as in ethanal, and an aldehyde is easily oxidised to the corresponding acid but is not itself acidic. Option D is wrong because the ketone group lies between two carbon atoms, as in propanone or acetone, and is likewise not acidic. A useful pair to remember is that ethanol oxidises to ethanoic acid.
Read the full article: Carbon and Its Compounds: Bonding, Allotropes and PYQs
Practice Questions
View allCooking gas (LPG) mainly consists of
- A.Ethene
- B.Ethyne
- C.Propene
- D.Propane and Butane
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Liquefied petroleum gas is a mixture of these two saturated hydrocarbons, which are gases at ordinary pressure but turn liquid under moderate pressure, so a large quantity of fuel fits into a small cylinder; a strong-smelling compound is added so that a leak is noticed.
Read the full explanation →How many isomers does C6H14 have?
- A.3
- B.6
- C.4
- D.5
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Hexane, C6H14, can be drawn as a straight chain of six carbons, as two chains of five carbons with a methyl branch in different positions, and as two chains of four carbons carrying branches, which gives five different structures with the same molecular formula.
Read the full explanation →Compounds with exactly two double carbon to carbon bonds are known as ______.
- A.Terpenes
- B.Dienes
- C.Trialkyne
- D.Dialkyne
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The prefix di stands for two and the ending ene for a carbon to carbon double bond, so a diene is a hydrocarbon carrying exactly two such bonds; buta-1,3-diene, the raw material of synthetic rubber, is the standard example.
Read the full explanation →The first member of the alkyne group of hydrocarbons is
- A.propyne
- B.ethyne
- C.methyne
- D.butyne
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An alkyne contains a carbon to carbon triple bond, which needs at least two carbon atoms, so the series begins with ethyne, C2H2, also called acetylene and used with oxygen in welding.
Read the full explanation →A gas stove flame burns blue because of
- A.Complete combustion of fuel
- B.Presence of hydrogen in the air
- C.Hazardous combustion
- D.Insufficient oxygen
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When enough air reaches the burner, every carbon atom of the fuel is oxidised fully to carbon dioxide and the flame is blue and hot, giving the maximum heat for the gas consumed.
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