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11.5. Alkenes
A subsection of Chemistry, 0620, through 11. Organic chemistry
Listing 10 of 149 questions
Hydrogen is the first element of the Periodic Table. Hydrogen is used in fuel cells to produce electricity in vehicles. Name the substance which combines with hydrogen in a fuel cell. Give one advantage and one disadvantage of using fuel cells instead of gasoline in vehicle engines. advantage disadvantage Hydrogen gas can be made from petroleum by a two-step procedure. step 1 Petroleum is separated into different components. step 2 Large molecules obtained in step 1 are converted into smaller molecules including hydrogen gas. Name the process used in step 1. Name the process used in step 2. Organic compounds contain hydrogen atoms. Calculate the number of hydrogen atoms in 44.0 g of the ester methyl propanoate, CH3CH2COOCH3. One mole of CH3CH2COOCH3 contains 6.02 × 1023 molecules. Give your answer in standard form. number of hydrogen atoms = For each of the homologous series shown, name a member that contains six hydrogen atoms. ● alkanes ● alkenes ● alcohols ● carboxylic acids Unsaturated alkenes are converted into saturated alkanes by reaction with hydrogen gas. State why alkenes and alkanes are hydrocarbons. State why alkenes are unsaturated. Name the catalyst needed to convert alkenes into alkanes. Explain why the conversion of alkenes into alkanes is an addition reaction.
0620_w24_qp_41
THEORY
2024
Paper 4, Variant 1
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Alkenes are manufactured by cracking larger alkane molecules. State the source of the large alkane molecules used in cracking. State two conditions needed for cracking large alkane molecules. When one molecule of dodecane, C12H26, is cracked, three molecules of but-1-ene and one other product are formed. Use molecular formulae to complete the symbol equation for this reaction. C12H26 → + Suggest the type of chemical reaction which happens during cracking. Propene will undergo polymerisation. Suggest the name of the polymer formed from propene. Draw part of this polymer molecule to show three repeat units. State the type of polymerisation propene undergoes.
0620_w24_qp_42
THEORY
2024
Paper 4, Variant 2
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Hydrocarbons are compounds which contain only carbon and hydrogen. 20 cm3 of a gaseous hydrocarbon was burned in 120 cm3 of oxygen, which is in excess. After cooling, the volume of the gases remaining was 90 cm3. Aqueous sodium hydroxide was added to remove carbon dioxide, 30 cm3 of oxygen remained. All volumes were measured at r.t.p Explain why it is essential to use excess oxygen. Carbon dioxide is slightly soluble in water. Why does it dissolve readily in the alkali, sodium hydroxide? Complete the following. volume of gaseous hydrocarbon = cm3 volume of oxygen used = cm3 volume of carbon dioxide formed = cm3 Use the above volume ratio to fi nd the mole ratio in the equation below and hence fi nd the formula of the hydrocarbon. CxHy+ O2→ CO2+ H2Ohydrocarbon formula = Alkanes are hydrocarbons and are generally unreactive. Their reactions include combustion, substitution and cracking. Chlorine reacts with butane in a substitution reaction. CH3 — CH2 — CH2 — CH3 + Cl 2 → CH3 — CH2 — CH2 — CH2 — Cl + HCl Give the structural formula of another possible product of this reaction. What is the essential condition for this reaction? Explain what is meant by cracking. Give an example of a cracking reaction and explain why the process is used.
0620_s11_qp_32
THEORY
2011
Paper 3, Variant 2
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Hydrocarbons are compounds which contain only carbon and hydrogen. 20 cm3 of a gaseous hydrocarbon was burned in 120 cm3 of oxygen, which is in excess. After cooling, the volume of the gases remaining was 90 cm3. Aqueous sodium hydroxide was added to remove carbon dioxide, 30 cm3 of oxygen remained. All volumes were measured at r.t.p Explain why it is essential to use excess oxygen. Carbon dioxide is slightly soluble in water. Why does it dissolve readily in the alkali, sodium hydroxide? Complete the following. volume of gaseous hydrocarbon = cm3 volume of oxygen used = cm3 volume of carbon dioxide formed = cm3 Use the above volume ratio to fi nd the mole ratio in the equation below and hence fi nd the formula of the hydrocarbon. CxHy+ O2→ CO2+ H2Ohydrocarbon formula = Alkanes are hydrocarbons and are generally unreactive. Their reactions include combustion, substitution and cracking. Chlorine reacts with butane in a substitution reaction. CH3 — CH2 — CH2 — CH3 + Cl 2 → CH3 — CH2 — CH2 — CH2 — Cl + HCl Give the structural formula of another possible product of this reaction. What is the essential condition for this reaction? Explain what is meant by cracking. Give an example of a cracking reaction and explain why the process is used.
0620_s11_qp_33
THEORY
2011
Paper 3, Variant 3
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Questions Discovered
149