uestions","formulaUrl":null,"initialIndex":56,"initialQuestionWindow":[{"id":"832facbe-f21c-4002-974a-5dc3d087844a","revisionId":"2e1a15fc-5b24-4004-9fab-7f658f866fa1","questionNumber":null,"questionType":"LA","specification":"Crude oil is separated into different fractions by fractional distillation.\n\n**Table 1** shows information about three of the hydrocarbon molecules found in three different fractions.\n\nTable 1\n| Molecule | Formula | Boiling point ($^\\circ\\text{C}$) |\n| :--- | :---: | :---: |\n| hexane | $\\text{C}_{6}\\text{H}_{14}$ | $69$ |\n| tetradecane | $\\text{C}_{14}\\text{H}_{30}$ | $254$ |\n| octacosane | $\\text{C}_{28}\\text{H}_{58}$ | $432$ |","difficulty":4,"difficultyBand":"medium","totalMarks":9,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"80ff17f5-0dc0-4911-8201-f291b9eb798e","label":"a","content":"Which of these three molecules would be separated **highest** up the fractionating column? Explain your answer using ideas about molecular size and boiling point.","markscheme":"- Identifies **hexane** as the molecule separated highest up the column B1\n- Explains that hexane is the smallest molecule (with the shortest carbon chain / weakest intermolecular forces) M1\n- Explains that hexane has the lowest boiling point, meaning it condenses at the top of the fractionating column where the temperature is lowest A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]},{"id":"550b56e1-4772-494a-a779-ca4127c2def2","label":"b","content":"Cracking breaks down large hydrocarbons produced in fractional distillation into smaller, more useful molecules. The chemical equation shows the cracking of octadecane:\n\n$$\\text{C}_{18}\\text{H}_{38} \\rightarrow \\text{C}_{12}\\text{H}_{26} + 3\\text{C}_2\\text{H}_4$$\n$$\\text{octadecane} \\rightarrow \\text{dodecane} + 3 \\times \\text{molecule }\\mathbf{Z}$$\n\nState the name of molecule $\\mathbf{Z}$, $\\text{C}_2\\text{H}_4$.","markscheme":"- States the name of molecule $\\mathbf{Z}$ is **ethene** B1","marks":1,"order":1,"markingRubric":null,"explanation":null,"options":[]},{"id":"7e3fd12c-3557-4a1d-9012-924ae1a95325","label":"c","content":"Molecule $\\mathbf{Z}$ has the general formula $\\text{C}_n\\text{H}_{2n}$. Octadecane and dodecane are both alkanes. State the general formula of the alkanes.","markscheme":"- States the general formula for alkanes is $\\text{C}_n\\text{H}_{2n+2}$ B1","marks":1,"order":2,"markingRubric":null,"explanation":null,"options":[]},{"id":"7827ec71-d916-4227-9cc0-881032be6d31","label":"d","content":"**Table 2** shows the percentage supply and percentage demand for some of the different fractions obtained from crude oil.\n\nTable 2\n| Fraction | Percentage supply (%) | Percentage demand (%) |\n| :--- | :---: | :---: |\n| LPG | $4$ | $6$ |\n| petrol | $9$ | $28$ |\n| naphtha | $12$ | $8$ |\n| kerosene | $14$ | [blank] |\n| diesel oil | $22$ | $27$ |\n| fuel oil | $39$ | $21$ |\n\nCalculate the percentage demand for kerosene.","markscheme":"- Sets up the equation for the remaining percentage: $100 - (6 + 28 + 8 + 27 + 21)$ M1\n- Calculates the percentage demand for kerosene as $10\\%$ A1","marks":2,"order":3,"markingRubric":null,"explanation":null,"options":[]},{"id":"d2eeddde-9600-481f-8c54-4c06715b2988","label":"e","content":"Suggest why fuel oil, rather than diesel oil, is cracked to obtain petrol.","markscheme":"- Explains that the supply of fuel oil ($39\\%$) exceeds its demand ($21\\%$), leaving a large surplus to be cracked B1\n- Explains that diesel oil is in short supply because its demand ($27\\%$) is greater than its supply ($22\\%$) B1","marks":2,"order":4,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"866a5b00-51ae-45ef-b3ed-fee81169c2cb","revisionId":"52c69d49-05e0-4631-be07-f72c6a09febe","questionNumber":null,"questionType":"MC","specification":"A bio-based polymer is synthesized

Organic chemistry

Question 27

Organic chemistry Questions

Organic chemistry

Question 27

Organic chemistry Questions