11. Organic chemistry
A section of Chemistry, 0620
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This question is about alkanes and alkenes. Short-chain alkanes and alkenes can be formed from long-chain alkanes in a chemical reaction. Name the type of chemical reaction which forms short‑chain alkanes and alkenes from long‑chain alkanes. Decane has 10 carbon atoms. It forms ethane and ethene as the only products in this type of chemical reaction. Write the chemical equation for this reaction. Ethane reacts with chlorine at room temperature to form chloroethane, C2H5Cl, and one other product. Name the other product formed. State the condition needed for this reaction to take place. Ethene reacts with chlorine at room temperature to form dichloroethane, C2H4Cl 2. C2H4 + Cl 2 → C2H4Cl 2 State why this is an addition reaction. The chemical equation for this reaction can be represented as shown. Cl Cl C H H C H H Cl Cl C C + H H H H The energy change for the reaction is –180 kJ / mol. Use the bond energies in the table to calculate the bond energy of a C–Cl bond, in kJ / mol. bond C–H C=C Cl –Cl C–C bond energy in kJ / mol Use the following steps. step 1 Calculate the energy needed to break bonds.  energy needed to break bonds = kJ step 2 Use your answer in step 1 and the energy change for the reaction to determine the energy released when bonds are formed.  energy released when bonds form = kJ step 3 Use your answer in step 2 and bond energy values to determine the energy of a C–Cl bond.  bond energy of a C–Cl bond = kJ / mol  
0620_m22_qp_42
THEORY
2022
Paper 4, Variant 2
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