IB Chemistry SL 3.4 Electron-Pair Sharing Reactions Question Bank

Practise IB Chemistry SL 3.4 with questions on nucleophiles, electrophiles, curly-arrow notation, substitution, addition and complex ions.

Covered syllabus points

3.4.1—Nucleophiles 3.4.2—Nucleophilic substitution 3.4.3—Heterolytic fission 3.4.4—Electrophiles 3.4.5—Electrophilic addition to alkenes 3.4.6—Lewis acid-base theory 3.4.7—Coordination bond formation 3.4.8—Complex ions

[Maximum number: 3]

Chlorine undergoes many reactions.

(a)

Predict, giving a reason, whether ethane or chloroethane is more reactive.

[ 1 ]

chloroethane AND C-Cl bond is weaker/ $324 \mathrm{~kJ} \mathrm{~mol}^{-1}$ than C-H bond $/ 414 \mathrm{~kJ} \mathrm{~mol}^{-1}$

OR

chloroethane AND contains a polar bond

Marking guidance:

Accept "chloroethane AND polar".

(b)

Write the equation for the reaction of chloroethane with a dilute aqueous solution of sodium hydroxide.

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{l})+\mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})$

OR
$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}(\mathrm{l})+\mathrm{NaOH}(\mathrm{aq}) \rightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq})$

Marking guidance:

Accept use of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ and $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} / \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ in the equation.

(c)

Deduce the nucleophile for the reaction in d(iii).

[ 1 ]

hydroxide «ion»/ $\mathrm{OH}^{-}$

Marking guidance:

Do not accept NaOH.

[Maximum number: 1]

Which row correctly shows heterolytic fission?

$\mathrm{Br} \underset{\mathrm{Br}}{\curvearrowleft} \rightarrow \mathrm{Br}^{+}+\mathrm{Br}^{-}$

$\mathrm{Br} \underset{\mathrm{Br}}{\curvearrowleft} \rightarrow 2 \mathrm{Br}$ .

$\mathrm{Br} \stackrel{\mathrm{Br}}{\mathrm{Br}} \rightarrow \mathrm{Br}^{+}+\mathrm{Br}^{-}$

$\mathrm{Br} \stackrel{\mathrm{Br}}{\mathrm{Br}} \rightarrow 2 \mathrm{Br}$ .

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Covered syllabus points

3.4 Electron-pair sharing reactions question 1

Question (a)

Question (b)

Question (c)

3.4 Electron-pair sharing reactions question 2