Chemistry 9701 · AS & A Level · Halogen compounds

Halogen compounds — practice question

(a)[2]

Explain the meaning of the term bond energy.

(b(i))

Describe and explain the pattern in bond energies for the C-X bond in halogenoalkanes, where $X = \text{F}, \text{Cl}, \text{Br}$ or $\text{I}$.

(b(ii))[3]

Describe the link between the reactivity of halogenoalkanes, $\text{RX}$, and the bond energies of the C-X bond.

(c)[3]

Use the Data Booklet to suggest why CFCs such as $\text{CF}_2\text{Cl}_2$ are far more harmful to the ozone layer than fluorocarbons such as $\text{CF}_4$ or hydrocarbons such as butane, $\text{C}_4\text{H}_{10}$.

(d)[3]

Predict the products of these reactions and draw their structures in the boxes below. The molecular formula of each product is given, where $X = \text{Cl}, \text{Br}$ or $\text{I}$.

(e(i))

State the conditions required for: $\text{C}_2\text{H}_6 + \text{Cl}_2 \rightarrow \text{C}_2\text{H}_5\text{Cl} + \text{HCl}$.

(e(ii))

State the reaction type in this case.

(e(iii))

Use the Data Booklet to calculate the enthalpy change, $\Delta H$, for the step: $\text{Cl}^\bullet + \text{CH}_3\text{CH}_3 \rightarrow \text{HCl} + \text{CH}_3\text{CH}_2^\bullet$.

(e(iv))

Use the Data Booklet to calculate the enthalpy change, $\Delta H$, for the comparable reaction: $\text{I}^\bullet + \text{CH}_3\text{CH}_3 \rightarrow \text{HI} + \text{CH}_3\text{CH}_2^\bullet$.

(e(v))

Hence suggest why making iodoethane by reacting iodine with ethane is not possible.

(e(vi))[8]

Complete these equations for some possible steps in making chloroethane.

Worked solution & mark scheme

This 19-mark question has a full step-by-step worked solution and mark scheme. One marking point: Energy change for breaking 1 mol of bonds in the gas phase

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