IB · IB Chemistry
IB Chemistry: Functional groups: classification of organic compounds — Practice Questions & Answers
428 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
What is the general formula of the alkanes?
- $\text{C}_{n}\text{H}_{2n+2}$
- $\text{C}_{n}\text{H}_{2n}$
- $\text{C}_{n}\text{H}_{2n-2}$
- $\text{C}_{n}\text{H}_{n}$
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WhyAlkanes are saturated hydrocarbons with the general formula $\text{C}_{n}\text{H}_{2n+2}$.
2
Multiple choice · Easy
Which functional group is characteristic of alcohols?
- $-\text{OH}$ (hydroxyl)
- $-\text{COOH}$ (carboxyl)
- $-\text{CHO}$ (aldehyde)
- $-\text{NH}_{2}$ (amine)
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WhyAlcohols contain the hydroxyl group, $-\text{OH}$.
3
Multiple choice · Medium
What is the IUPAC name of $\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{OH}$?
- Propan-1-ol
- Propan-2-ol
- Propanal
- Propanoic acid
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WhyA three-carbon chain with an -OH on the end carbon is propan-1-ol.
4
Multiple choice · Medium
Which functional group is found in carboxylic acids?
- $-\text{COOH}$
- $-\text{OH}$
- $-\text{CO}-$
- $-\text{O}-$
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WhyCarboxylic acids contain the carboxyl group, $-\text{COOH}$.
5
Multiple choice · Medium
Successive members of a homologous series differ by:
- $\text{CH}_{2}$
- $\text{CH}_{3}$
- $\text{C}_{2}\text{H}_{4}$
- $\text{H}_{2}$
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WhyEach member of a homologous series differs from the next by a $\text{CH}_{2}$ unit (and by $14\,\text{g mol}^{-1}$).
6
Multiple choice · Hard
Which compound is a structural isomer of butane?
- 2-methylpropane
- Propane
- Pentane
- But-1-ene
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Why2-methylpropane has the same molecular formula ($\text{C}_{4}\text{H}_{10}$) as butane but a branched chain, so it is a structural isomer.
7
Fill in the blank · Easy
The functional group present in alkenes is a carbon-carbon bond.
Answer:
double / double bond
WhyAlkenes are unsaturated and contain a C=C double bond as their functional group.
8
Fill in the blank · Medium
The molecule pentane contains carbon atoms.
Answer:
5 / five
WhyThe prefix pent- denotes a chain of 5 carbon atoms, so pentane is $\text{C}_{5}\text{H}_{12}$.
9
Multiple choice · Medium
What is a limitation of infrared (IR) spectroscopy for structure determination?
- It identifies bonds present but not their position in the molecule
- It destroys the chemical structure of the sample
- It can only measure molar mass
- It cannot detect any bonds
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WhyIR spectroscopy identifies the bonds and functional groups present but does not show where those groups are located in the molecule.
10
Multiple choice · Medium
What does an IR spectrum mainly allow a chemist to identify?
- The functional groups and bonds present
- The exact relative molecular mass
- The number of carbon atoms only
- The optical rotation of the sample
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WhyAbsorptions at characteristic wavenumbers reveal which bonds and functional groups are present.
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