Chemistry 9701 · AS & A Level · Halogen compounds

Halogen compounds — practice question

(a)[2]

Explain what the term bond energy means.

(b(i))[2]

Describe and explain the pattern in the bond energies of 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, 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 damaging 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 the reactions shown, then draw their structures. The molecular formula for each product is provided.

(e(i))[1]

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

(e(ii))[1]

State the reaction type taking place here.

(e(iii))[2]

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))[2]

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

(e(v))[2]

Hence suggest why iodoethane cannot be made by reacting iodine with ethane.

(e(vi))[8]

Complete the equations for some possible steps in the formation of chloroethane.

Worked solution & mark scheme

This 29-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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