11.4. Alkanes
A subsection of Chemistry, 0620, through 11. Organic chemistry
Listing 10 of 57 questions
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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Propane reacts with chlorine in a photochemical reaction as shown. C3H8 + Cl 2 → C3H7Cl + HCl What type of reaction is this? What condition is needed for this photochemical reaction to occur? Draw two structural isomers of compounds with the formula C3H7Cl. Show all of the atoms and all of the bonds.  Propene reacts with chlorine in an addition reaction as shown. C3H6 + Cl 2 → C3H6Cl 2 State why this is an addition reaction. The structures of the reactants and products of this reaction are shown. H C H H C H H C Cl Cl H + → H H C H H Cl Cl C H C H Some bond energies are shown in the table. bond bond energy in kJ / mol C–C C=C C–H C–Cl Cl –Cl Calculate the energy change for the reaction between propene and chlorine using the following steps. ● ● Calculate the energy needed to break the bonds.  kJ ● ● Calculate the energy released when bonds are formed.  kJ ● ● Calculate the energy change for the reaction between propene and chlorine.  kJ / mol  There are three functional groups in compoundA. C COOH H C compound A CH2OH H Name the homologous series of compounds that contains the following structures. C=C –OH –COOH  What would you observe when compoundA is added to: aqueous bromine aqueous sodiumcarbonate?  CompoundA can be used as a single monomer to produce two different polymers. Draw one repeat unit of the addition polymer formed from compoundA.  What type of condensation polymer is formed from compoundA? 
0620_s20_qp_42
THEORY
2020
Paper 4, Variant 2
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Chlorine is in GroupVII of the PeriodicTable. Two isotopes of chlorine are chlorine‑35 and chlorine‑37. State why these two isotopes of chlorine have the same chemical properties. Complete the table to show the number of electrons, neutrons and protons in each atom and ion. number of electrons number of neutrons number of protons 35Cl 37Cl –  Chlorine reacts with aqueous sodium bromide. The equation for the reaction is shown. Cl 2 + 2NaBr → 2NaCl + Br2 State the type of reaction shown. Why is there no reaction between iodine and aqueous sodium bromide? Magnesium reacts with chlorine to form magnesiumchloride. Complete the dot-and-cross diagram to show the electron arrangement of the ions in magnesiumchloride. Give the charges on the ions. The inner shells have been completed. Cl Mg  Hydrogen and chlorine react to form hydrogenchloride gas, as shown in the equation. H2 + Cl 2 → 2HCl This equation can be represented as shown. H–H + Cl –Cl → 2H–Cl Some bond energies are shown in the table. bond bond energy in kJ / mol H–H Cl –Cl H–Cl Calculate the energy change for the reaction between hydrogen and chlorine, using the following steps. ● ● Calculate the energy needed to break the bonds.  kJ ● ● Calculate the energy released when bonds are formed.  kJ ● ● Calculate the energy change for the reaction.  kJ / mol  
0620_s20_qp_43
THEORY
2020
Paper 4, Variant 3
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