Chapter Five · Alcohols and phenols: practice questions
Chapter Five · Organic chemistry · Chemistry. These are 10 questions from the Magmo3 bank on this lesson, from easy to hard. Solve each one, then open "Show answer and explanation". Magmo3 has 110 questions on this lesson, each with an explanation.
During the esterification of ethanoic acid with ethanol, the water molecule that is eliminated is formed from:
ATwo -OH groups belonging to the alcohol
BThe carbonyl oxygen of the acid only
CThe -OH of the acid and the -H of the alcohol's hydroxyl group
DThe -OH of the alcohol and the -H of the acid's methyl group
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Correct answer: (C) The -OH of the acid and the -H of the alcohol's hydroxyl group
Explanation: In the standard esterification scheme, the -OH is removed from the carboxylic acid and the -H from the alcohol to form water.
Question 2Easy
Oxidation of a secondary alcohol with acidified potassium permanganate produces:
Aan aldehyde
Ba ketone
Cno reaction
Da carboxylic acid
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Correct answer: (B) a ketone
Explanation: Secondary alcohols are oxidised to ketones, which resist further oxidation.
Question 3Easy
Why is pure ethanol of 96% concentration expensive?
ABecause of the high production tax which should be paid for it
BBecause it is very difficult to synthesize in the laboratory
CBecause it is imported from foreign countries
DBecause it requires very complicated chemical processes to purify
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Correct answer: (A) Because of the high production tax which should be paid for it
Explanation: Pure ethanol of 96% concentration is expensive because of the high production tax which should be paid for it.
Question 4Medium
How many different isomeric alcohols can be derived from pentane?
A2
B4
C5
D3
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Correct answer: (D) 3
Explanation: 'From pentane we can derive 3 different isomeric alcohols' (1-pentanol, 2-pentanol, and 3-pentanol).
Question 5Medium
What is the IUPAC name of the alcohol (CH3)2CH–CH2–OH?
Abutan-2-ol
B2-methylpropan-2-ol
Cbutan-1-ol
D2-methylpropan-1-ol
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Correct answer: (D) 2-methylpropan-1-ol
Explanation: The longest chain bearing the –OH is three carbons with a methyl branch on C2, giving 2-methylpropan-1-ol.
Question 6Medium
Why are ethanol and similar compounds obtained from petroleum referred to as 'petrochemical compounds'?
ABecause they are naturally occurring minerals found in crude oil deposits
BBecause they are chemicals produced from petroleum
CBecause they can only be synthesized at petroleum refinery temperatures above 500°C
DBecause they are used exclusively as engine fuels
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Correct answer: (B) Because they are chemicals produced from petroleum
Explanation: Petrochemical compounds by stating: 'Therefore, ethanol is considered as a petrochemical compound (chemicals that produced from petroleum).'.
Question 7Medium
What is the result of hydrolyzing sodium ethoxide with water?
AEthanol and sodium hydroxide
BMethanol and sodium hydroxide
CEthanol and sodium chloride
DEthyl bromide and sodium oxide
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Correct answer: (A) Ethanol and sodium hydroxide
Explanation: The equation: 'C₂H₅ONa + H₂O(l) → C₂H₅OH + NaOH (aq)' which yields ethanol and sodium hydroxide.
Question 8Hard
What property causes alcohols to have relatively high boiling points and complete solubility in water compared to alkanes?
AThe presence of non-polar covalent bonds in their alkyl radicals
BTheir neutral effect on litmus paper
CThe presence of the polar hydroxyl groups which form hydrogen bonds
DTheir ability to react with strong active metals like sodium
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Correct answer: (C) The presence of the polar hydroxyl groups which form hydrogen bonds
Explanation: The solubility in water and the high boiling points of alcohols are attributed to the presence of the polar hydroxyl groups which have the ability of forming hydrogen bonds...
Question 9Hard
In the ester formation reaction between an organic acid and an alcohol containing heavy oxygen isotope O¹⁸, where does the O¹⁸ isotope end up according to isotopic analysis of the products?
AIn the water molecule formed during the reaction
BIn the carbonyl oxygen of the organic acid
CIt is completely lost as oxygen gas
DIn the formed ester molecule
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Correct answer: (D) In the formed ester molecule
Explanation: By reacting alcohol containing the heavy oxygen isotope O¹⁸ with acetic acid containing the normal oxygen isotope O¹⁶, analyzing the oxygen of the formed water found that it is of the normal isotope, meaning O¹⁸ remains in the ester.
Question 10Hard
An alcohol is oxidised by acidified potassium dichromate to a ketone and, on dehydration with concentrated sulphuric acid at 180 °C, gives but-2-ene as the major product. The alcohol is:
A2-methylpropan-2-ol
Bbutan-2-ol
C2-methylpropan-1-ol
Dbutan-1-ol
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Correct answer: (B) butan-2-ol
Explanation: Butan-2-ol is a secondary alcohol (oxidised to butanone) and dehydrates to but-2-ene as the major alkene.