14.1. Alkanes
A subsection of Chemistry, 9701, through 14. Hydrocarbons
Listing 10 of 122 questions
Most submarines travel under water using electrical power from batteries. The German engineer Helmut Walter designed a diesel engine that could be used to propel a submarine beneath the surface of the sea. Instead of taking air from above the surface of the sea, Walter’s engine used hydrogen peroxide, H2O2, to provide oxygen for a conventional diesel engine. Hydrogen peroxide may be catalytically decomposed to give water and oxygen. What is meant by the term catalyst? Construct a balanced equation for the decomposition of H2O2. Diesel fuel may be considered to consist of the hydrocarbon C15H32 which reacts completely with oxygen according to the following equation. C15H32 + 23O2 → 15CO2 + 16H2O To which homologous series does C15H32 belong? Use the equation above and your answer to to calculate the amount, in moles, of H2O2, that will provide sufficient oxygen for the complete oxidation of one mole of C15H32. amount of H2O2 = mol A submarine equipped with a Walter engine used 212 tonnes of diesel fuel during an underwater voyage. The submarine also carried concentrated aqueous H2O2. [1 tonne = 106g] Calculate the amount, in moles, of diesel fuel used during the underwater voyage. amount of diesel fuel = mol Use your answers to and to calculate the mass, in tonnes, of hydrogen peroxide used during the underwater voyage. mass of H2O2 = tonnes The exhaust products of the Walter engine were passed into the sea. What would happen to them?
9701_w08_qp_2
THEORY
2008
Paper 2, Variant 0
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Astronomers using modern spectroscopic techniques of various types have found evidence of many molecules, ions and free radicals in the dust clouds in Space. Many of the species concerned have also been produced in laboratories on Earth. Two such species are the dicarbon monoxide molecule, C2O, and the amino free radical, NH2. Dicarbon monoxide can be produced in a laboratory and analysis of it shows that the sequence of atoms in this molecule is carbon-carbon-oxygen and there are no unpaired electrons, but one of the atoms is only surrounded by six electrons. Draw a ‘dot-and-cross’ diagram of C2O and suggest the shape of the molecule. shape What is meant by the term free radical ? Explain why NH2 is described as a ‘free radical’. Two derivatives of ethene which have been detected in dust clouds in Space are acrylonitrile (2-propenenitrile), CH2=CHCN, and vinyl alcohol , CH2=CHOH. Like ethene, acrylonitrile can be polymerised. The resulting polymer can be used to make carbon fibres. Draw the structural formula of the polymer made from acrylonitrile, showing two repeat units. What type of polymerisation is this reaction? Vinyl alcohol cannot be polymerised in the same way as acrylonitrile because it will readily isomerise into another common organic compound, Z. Suggest the structural formula of the organic compound Z. Suggest the structural formula of another isomer of vinyl alcohol which has a cyclic structure. Acrolein (2-propenal), CH2=CHCHO, has also been found in Space. Give the structural formulae of the organic compounds formed when acrolein is reacted separately with each of the following reagents. reagent product Br2 in an inert solvent NaCN + dilute H2SO4 Tollens’ reagent NaBH4
9701_w10_qp_23
THEORY
2010
Paper 2, Variant 3
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Questions Discovered
122