IB · IB Chemistry

IB Chemistry: Electron-pair sharing reactions — Practice Questions & Answers

124 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

A nucleophile is best described as a species that:

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WhyA nucleophile is an electron-rich species that donates a lone pair of electrons to form a new bond (a Lewis base).
2 Multiple choice · Easy

Alkenes characteristically undergo which type of reaction with electrophiles?

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WhyThe electron-rich C=C double bond of an alkene attracts electrophiles, so alkenes undergo electrophilic addition.
3 Multiple choice · Medium

A Lewis acid is defined as a species that:

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WhyA Lewis acid is an electron-pair acceptor, whereas a Lewis base is an electron-pair donor.
4 Multiple choice · Medium

What is the organic product when bromine, $\text{Br}_{2}$, adds across the double bond of ethene?

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WhyElectrophilic addition of $\text{Br}_{2}$ to ethene gives 1,2-dibromoethane, $\text{CH}_{2}\text{BrCH}_{2}\text{Br}$, and decolourises the bromine.
5 Multiple choice · Medium

When a halogenoalkane reacts with aqueous hydroxide ions, $\text{OH}^{-}$, the organic product is:

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WhyThe hydroxide ion acts as a nucleophile, substituting the halogen to form an alcohol, e.g. $\text{CH}_{3}\text{Br} + \text{OH}^{-} \rightarrow \text{CH}_{3}\text{OH} + \text{Br}^{-}$.
6 Multiple choice · Hard

Which species acts as the electrophile in the addition of $\text{HBr}$ to propene?

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WhyThe $\text{H}^{\delta+}$ end of the polar H-Br bond is electron-deficient and attacks the electron-rich double bond, so $\text{H}^{+}$ (from HBr) is the electrophile.
7 Fill in the blank · Easy

An electron-pair acceptor is known as a Lewis .

Answer: acid

WhyA Lewis acid accepts a pair of electrons to form a coordinate (dative) covalent bond.
8 Fill in the blank · Medium

Orange bromine water is decolourised when shaken with an , because the C=C double bond undergoes addition.

Answer: alkene / alkene (unsaturated compound)

WhyAlkenes (unsaturated hydrocarbons) decolourise bromine water by electrophilic addition; alkanes do not. This is the test for unsaturation.
9 Multiple choice · Medium

What is the product of the addition of HBr to but-2-ene?

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WhyHBr adds across the double bond of the symmetrical alkene to give 2-bromobutane.
10 Multiple choice · Medium

Which type of reaction occurs when bromine adds across the C=C bond of an alkene?

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WhyAlkenes undergo electrophilic addition across the double bond.

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Practise other IB Chemistry topics

Topic S1.1 (SL/HL): Introduction to the particulate nature of matter Topic S1.2 (SL/HL): The nuclear atom Topic S1.2 (HL): The nuclear atom Topic S1.3 (SL/HL): Electron configurations Topic S1.3 (HL): Electron configurations Topic S1.4 (SL/HL): Counting particles by mass: the mole Topic S1.5 (SL/HL): Ideal gases Topic S2.1 (SL/HL): The ionic model Topic S2.1 (HL): The ionic model Topic S2.2 (SL/HL): The covalent model Topic S2.2 (HL): The covalent model Topic S2.3 (SL/HL): The metallic model Topic S2.3 (HL): The metallic model Topic S2.4 (SL/HL): From models to materials Topic S2.4 (HL): From models to materials Topic S3.1 (SL/HL): The periodic table: classification of elements Topic S3.1 (HL): The periodic table: classification of elements Topic S3.2 (SL/HL): Functional groups: classification of organic compounds Topic S3.2 (HL): Functional groups: classification of organic compounds Topic R1.1 (SL/HL): Measuring enthalpy changes Topic R1.2 (SL/HL): Energy cycles in reactions Topic R1.2 (HL): Energy cycles in reactions Topic R1.3 (SL/HL): Energy from fuels Topic R1.4 (HL): Entropy and spontaneity Topic R2.1 (SL/HL): How much? The amount of chemical change Topic R2.2 (SL/HL): How fast? The rate of chemical change Topic R2.2 (HL): How fast? The rate of chemical change Topic R2.3 (SL/HL): How far? The extent of chemical change Topic R2.3 (HL): How far? The extent of chemical change Topic R3.1 (SL/HL): Proton transfer reactions Topic R3.1 (HL): Proton transfer reactions Topic R3.2 (SL/HL): Electron transfer reactions Topic R3.2 (HL): Electron transfer reactions Topic R3.3 (SL/HL): Electron sharing reactions Topic R3.4 (HL): Electron-pair sharing reactions