9701_w10_qp_21
A paper of Chemistry, 9701
Questions:
5
Year:
2010
Paper:
2
Variant:
1
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1
Examiner s Use In 1814, Sir Humphrey Davy and Michael Faraday collected samples of a flammable gas, A, from the ground near Florence in Italy. They analysed A which they found to be a hydrocarbon. Further experiments were then carried out to determine the molecular formula of A. What is meant by the term molecular formula? Davy and Faraday deduced the formula of A by exploding it with an excess of oxygen and analysing the products of combustion. Complete and balance the following equation for the complete combustion of a hydrocarbon with the formula CxHy . CxHy + (x + y 4)O2 + When 10 cm3 of A was mixed at room temperature with 50 cm3 of oxygen (an excess) and exploded, 40 cm3 of gas remained after cooling the apparatus to room temperature and pressure. When this 40 cm3 of gas was shaken with an excess of aqueous potassium hydroxide, KOH, 30 cm3 of gas still remained. What is the identity of the 30 cm3 of gas that remained at the end of the experiment? The combustion of A produced a gas that reacted with the KOH. What is the identity of this gas? What volume of the gas you have identified in was produced by the combustion of A? cm3 What volume of oxygen was used up in the combustion of A? cm3 For Examiner’s Use Use your equation in and your results from and to calculate the molecular formula of A. Show all of your working.
2. Atoms, molecules and stoichiometry  →  2.4. Reacting masses and volumes (of solutions and gases)
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
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For Examiner’s Use Nitrogen makes up about 79% of the Earth’s atmosphere. As a constituent element of proteins, it is present in living organisms. Atmospheric nitrogen is used in the Haber process for the manufacture of ammonia. Write an equation for the formation of ammonia in the Haber process. The Haber process is usually carried out at a high pressure of between 60 and 200 atmospheres (between 60 × 105 Pa and 200 × 105 Pa). State two further important operating conditions that are used in the Haber process. For each of your conditions, explain why it is used. condition 1 reason condition 2 reason State one large-scale use for ammonia, other than in the production of nitrogenous fertilisers. The uncontrolled use of nitrogenous fertilisers can cause environmental damage to lakes and streams. This is known as ‘eutrophication’. What are the processes that occur when excessive amounts of nitrogenous fertilisers get into lakes and streams? For Examiner’s Use In many countries, new cars have to comply with regulations which are intended to reduce the pollutants coming from their internal combustion engines. Two pollutants that may be formed in an internal combustion engine are carbon monoxide, CO, and nitrogen monoxide, NO. Outline how each of these pollutants may be formed in an internal combustion engine. CO NO State the main hazard associated with each of these pollutants. CO NO Pollutants such as CO and NO are removed from the exhaust gases of internal combustion engines by catalytic converters which are placed in the exhaust system of a car. What metal is most commonly used as the catalyst in a catalytic converter? Construct one balanced equation for the reaction in which both CO and NO are removed from the exhaust gases by a catalytic converter.
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
14. Hydrocarbons  →  14.1. Alkanes
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For Examiner’s Use Crude oil is a naturally occurring flammable liquid which consists of a complex mixture of hydrocarbons. In order to separate the hydrocarbons the crude oil is subjected to fractional distillation. Explain what is meant by the following terms. hydrocarbon fractional distillation Undecane, C11H24, is a long chain hydrocarbon which is present in crude oil. Such long chain hydrocarbons are ‘cracked’ to produce alkanes and alkenes which have smaller molecules. Give the conditions for two different processes by which long chain molecules may be cracked. process 1 process 2 Undecane, C11H24, can be cracked to form pentane, C5H12, and an alkene. Construct a balanced equation for this reaction. Pentane, C5H12, exhibits structural isomerism. Draw the three structural isomers of pentane. isomer B isomer C isomer D For Examiner’s Use The three isomers of pentane have different boiling points. Which of your isomers has the highest boiling point? isomer Suggest an explanation for your answer. The unsaturated hydrocarbon, E, is obtained by cracking hexane and is important in the chemical industry. The standard enthalpy change of combustion of E is –2059 kJ mol–1. Define the term standard enthalpy change of combustion. When 0.47 g of E was completely burnt in air, the heat produced raised the temperature of 200 g of water by 27.5 °C. Assume no heat losses occurred during this experiment. Use relevant data from the Data Booklet to calculate the amount of heat released in this experiment. Use the data above and your answer to to calculate the relative molecular mass, Mr, of E. Deduce the molecular formula of E.
14. Hydrocarbons  →  14.1. Alkanes
14. Hydrocarbons  →  14.2. Alkenes
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For Examiner’s Use Halogenoalkanes have many chemical uses, particularly as intermediates in organic reactions. Three reactions of 1-bromobutane, CH3CH2CH2CH2Br, are shown below. CH3CH2CH2CH2OH CH3CH2CH2CH2NH2 CH3CH2CH2CH2Br CH3CH2CH=CH2 reaction 1 reaction 2 reaction 3 For each reaction, state the reagent and solvent used. reaction 1 reagent solvent reaction 2 reagent solvent reaction 3 reagent solvent When 1-iodobutane, CH3CH2CH2CH2I, is reacted under the same conditions as those used in reaction 1, butan-1-ol is formed. What difference, if any, would there be in the rate of this reaction compared to the reaction of 1-bromobutane? Use appropriate data from the Data Booklet to explain your answer. For Examiner’s Use Dichlorodifluoromethane, CCl2F2, is an example of a chlorofluorocarbon (CFC) that was formerly used as an aerosol propellant. In September 2007, at the Montreal summit, approximately 200 countries agreed to phase out the use of CFCs by 2020. State two properties of CFCs that made them suitable as aerosol propellants. 1. 2. When CFCs are present in the upper atmosphere, homolytic fission takes place in the presence of ultraviolet light. What is meant by the term homolytic fission? Suggest an equation for the homolytic fission of CCl2F2. The most common replacements for CFCs as aerosol propellants are hydrocarbons such as propane and butane. Suggest one disadvantage of these compounds as aerosol propellants.
15. Halogen compounds  →  15.1. Halogenoalkanes
14. Hydrocarbons  →  14.1. Alkanes
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For Examiner’s Use The gaseous hydrogen halides HCl, HBr and HI, may be prepared by reacting the corresponding sodium salt with anhydrous phosphoric(acid, H3PO4. When the sodium halide NaX was used, the following reaction occurred and a sample of gaseous HX was collected in a gas jar. NaX + H3PO4 NaH2PO4 + HX A hot glass rod was placed in the sample of HX and immediately a red/orange colour was observed. What is the identity of NaX? What gas, other than HX, would be formed if concentrated sulfuric acid were used with NaX instead of phosphoric(acid? Suggest why phosphoric(acid rather than concentrated sulfuric acid is used to make samples of HX from the corresponding sodium salt. Explain your answer.
11. Group 17  →  11.2. The chemical properties of the halogen elements and the hydrogen halides
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
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