Unit notes and practice questions
Everything here is for unit 6 of the Grade 11 Chemistry textbook: what the chapter covers, the short notes, practice questions with their answers, and the lesson video where one exists.
The cards filed under this chapter on the Grade 11 Chemistry page. Open one at a time.
When you use it
Use when determining whether heating ethanol with concentrated sulfuric acid produces an alkene or an ether.
Watch out
Do not confuse the reaction temperatures: elimination to ethene requires 170 °C, while condensation to diethyl ether occurs at 140 °C.
Drafted from Grade 11 Chemistry, page 264 onwards, then checked twice before it went up
When you use it
Use when preparing symmetrical or unsymmetrical ethers from an alkyl halide and an alkoxide ion.
Watch out
This nucleophilic substitution attaches the alkoxide oxygen directly to the alkyl carbon that held the halogen.
Drafted from Grade 11 Chemistry, page 264 onwards, then checked twice before it went up
| Family | The group | How you recognise it |
|---|---|---|
| Alcohol | The oxygen carries a hydrogen and is bonded to one carbon. Ethanol, . | |
| Ether | The oxygen sits between two carbons and carries no hydrogen. Methoxymethane, . | |
| Aldehyde | The carbonyl carbon is at the end of the chain and still holds a hydrogen. Ethanal, . | |
| Ketone | The carbonyl carbon sits inside the chain, with a carbon on each side. Propanone, . | |
| Carboxylic acid | A carbonyl and a hydroxyl on the same carbon. Ethanoic acid, . | |
| Ester | The carbonyl carbon is joined to an oxygen that carries a second carbon. Methyl ethanoate, . | |
| Primary amine | A nitrogen with three single bonds and no carbonyl beside it. Ethanamine, . | |
| Amide | The nitrogen is bonded straight to a carbonyl carbon. Ethanamide, . |
When you use it
Use when a structure or a condensed formula is in front of you and you have to name its family before you can name the compound or say how it reacts. Read what the oxygen or the nitrogen is attached to, then find that description in this table.
Watch out
Students name the family from the presence of an oxygen instead of from where the oxygen sits, so all of these end up called alcohols. If the oxygen carries a hydrogen it is an alcohol, ; if it sits between two carbons it is an ether, . Both are : the same atoms in two different families. The same test runs down the rest of the table. A carbonyl at the end of the chain with a hydrogen on it is an aldehyde, the same carbonyl with a carbon on both sides is a ketone, and in the second oxygen holds a hydrogen while in it holds a carbon.
| Family | Functional group | General formula | Example |
|---|---|---|---|
| Alcohol | ethanol, | ||
| Ether | methoxymethane, | ||
| Aldehyde | ethanal, | ||
| Ketone | propanone, | ||
| Carboxylic acid | ethanoic acid, | ||
| Primary amine | ethanamine, | ||
| Haloalkane | chloroethane, |
When you use it
Use when a question gives you a general formula such as or and asks which family it names, or when you have written a group down and want to check it against the family you meant. Each row is one homologous series: its members share this group and this general formula, and neighbouring members differ by one unit, which is 14 g/mol.
Watch out
Students write the aldehyde as instead of . Read it letter by letter: is a carbon holding a hydroxyl, which is an alcohol, so one swapped letter changes the whole family. The hydrogen comes before the oxygen. The same care separates the aldehyde from the ketone. Both hold a , but in an aldehyde that carbon still holds a hydrogen and therefore sits at the end of the chain, , while in a ketone it is trapped between two carbons, .
10 multiple-choice questions written against this chapter, each with its answer and the reason. Try one before you open the answer.
Question 1
Which group is the functional group of an alcohol?
Answer: B <p>Hydroxyl group (-OH)</p>
Why
The functional group of an alcohol is the hydroxyl group, -OH. It gives alcohols their special chemical and physical properties.
Question 2
Which of these is a monohydric alcohol?
Answer: C <p>1-Propanol</p>
Why
A monohydric alcohol has only one hydroxyl (-OH) group. 1-Propanol has one -OH group. The other three choices have two or three -OH groups.
Question 3
Propane-1,2,3-triol, also called glycerol, is which type of alcohol?
Answer: D <p>Trihydric</p>
Why
The name shows three -OH groups (the 1,2,3 positions). Alcohols with three hydroxyl groups are called trihydric alcohols.
Question 4
A student in Addis Ababa compares Tella, Tej, beer and wine. Which alcohol is present in all of these alcoholic beverages?
Answer: A <p>Ethanol</p>
Why
The textbook says that the only alcohol present in all alcoholic beverages is ethanol. Methanol, 1-butanol and glycerol are not in all of them.
Question 5
Which of these is a primary (1°) alcohol?
Answer: D <p>1-Butanol</p>
Why
In a primary alcohol, the carbon with the -OH group is attached to only one alkyl group. In 1-butanol, the -OH is on carbon 1, which is joined to only one other carbon. The other three are secondary or tertiary alcohols.
Question 6
2-Propanol is oxidized with a strong oxidizing agent. Which compound is the product?
Answer: C <p>Propanone (acetone)</p>
Why
Oxidation of a secondary alcohol gives a ketone. 2-Propanol is a secondary alcohol, so it is oxidized to propanone (acetone), as shown in Example 6.17 of your textbook.
Question 7
Ethanol is heated at 170 °C with concentrated H2SO4. What is the main organic product?
Answer: A <p>Ethene</p>
Why
At 170 °C, with concentrated sulphuric acid, ethanol loses a molecule of water (dehydration). This gives ethene and water: CH3CH2OH to CH2=CH2 + H2O.
Question 8
Ethanol boils at 78 °C, but its isomer dimethyl ether boils at -24 °C. What is the main reason for this difference?
Answer: C <p>The polar O-H group in ethanol forms hydrogen bonds between molecules.</p>
Why
The textbook says the difference is due to the polar O-H group in ethanol, which forms intermolecular hydrogen bonds. Dimethyl ether has no O-H group, so its molecules are held together only by weak dipole-dipole forces.
Question 9
In the Williamson ether synthesis, butyl iodide (CH3CH2CH2CH2I) reacts with the ethoxide ion (CH3CH2O-). Which ether is formed?
Answer: B <p>Butyl ethyl ether</p>
Why
In the Williamson synthesis, an alkyl halide reacts with an alkoxide ion to form an ether. The butyl group from butyl iodide joins to the oxygen of the ethoxide ion, giving butyl ethyl ether, as in Example 6.23 of your textbook.
Question 10
Ethylbenzene is heated with alkaline KMnO4. Which compound is formed?
Answer: A <p>Benzoic acid</p>
Why
The textbook says that an alkyl group on a benzene ring is oxidized to a carboxyl group, whatever its size. Both toluene and ethylbenzene give benzoic acid when refluxed with KMnO4 in alkaline medium.
The app holds 12 questions on this unit, marked as you go. These are the first 10.
The whole Grade 11 Chemistry textbook, free as a PDF.
Ministry of Education edition, English, 342 pages
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