Edexcel-Model Paper-Unit 2-Paper13

Transcription

1 Edexcel-Model Paper-Unit 2-Paper13 1. (a) But-2-ene, CH 3 CH=CHCH 3, exists as geometric isomers. Draw the geometric isomers of but-2-ene. Explain how geometric isomerism arises. (b) Draw the structural formula of a compound which is an isomer of but-2-ene but which does not show geometric isomerism. Explain why the isomer drawn in does not show geometric isomerism. (Total 5 marks) 2. Aluminium metal is manufactured by a process in which purified bauxite, dissolved in molten cryolite, is electrolysed at 800 C. Graphite electrodes and a current of about amperes are used. (a) Give the ionic equations for the reactions taking place at each electrode. Anode... Cathode... State which of these reactions is an oxidation process. Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 1

2 (iii) Explain why the anodes need to be replaced frequently. (iv) Explain why an electrolyte of pure molten bauxite is not used. (b) The production of aluminium is expensive. Explain why, despite this high cost, aluminium is manufactured in large quantities. Explain why it is worthwhile to recycle aluminium. (Total 11 marks) Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 2

3 3. Many of the natural compounds which are responsible for aromas in perfumes were first extracted from plants. Geraniol is found in roses and citral in lemon grass. (CH ) C CHCH CH C CHCH OH (CH ) C CHCH CH C CHC O CH CH H 3 3 geraniol citral Both of these are attractants for honey bees whereas (CH ) CHCH CH OC CH 3 O 3 methylbutyl ethanoate is a bee alarm pheromone and signifies danger to a honey bee but is also the principal cause of the smell of bananas. (a) Describe how infra-red spectroscopy could be used to distinguish between geraniol and citral. (b) Suggest the reagents and conditions necessary to convert geraniol to citral in the laboratory. Describe a chemical test you could do to check that geraniol has been converted to citral. (c) What type of compound is 3-methylbutyl ethanoate? (iii) (iv) If 3-methylbutyl ethanoate is warmed with aqueous sodium hydroxide solution a slow reaction takes place to produce sodium ethanoate and another product, A. Suggest the name of the other product A. This reaction is first order with respect to both 3-methylbutyl ethanoate and the aqueous hydroxide ion. Explain the term first order and give experimental details showing how this information could be obtained. Suggest the identity of the organic product if A is treated with phosphorus pentachloride. Give the equation for the reaction. (8) (v) If A is oxidised it produces a carboxylic acid (CH 3 ) 2 CHCH 2 CO 2 H. This acid has a boiling temperature of 176 ºC. 3-methylbutyl ethanoate has a boiling temperature of 142 ºC. Comment on the intermolecular forces involved in the two liquids and hence account for the relative values of their boiling temperatures. (5) (Total 25 marks) Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 3

4 4. Methane, CH 4, chloromethane, CH 3 Cl, and methanol, CH 3 OH, have molecules with similar shapes but they have different boiling temperatures. Compound Boiling temperature / C Methane 162 Chloromethane 24 Methanol +65 (a) Draw a dot and cross diagram to show the bonding in chloromethane. You need only draw the outer electrons of the atoms. (b) Draw a diagram to show the shape of the chloromethane molecule and explain why it has this shape (c) Explain why the boiling temperature of chloromethane is higher than that of methane. (d) Explain why the boiling temperature of methanol is higher than that of chloromethane. Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 4 (4)

5 (Total 11 marks) 5. Aluminium is obtained from the ore bauxite. (a) The first stage is the purification of the ore. State the formula of the aluminium compound present in bauxite. Identify the two major impurities in bauxite. (iii) Explain, in terms of the properties of the substances in bauxite, why the addition of 10% sodium hydroxide solution is used to separate the aluminium compound from the impurities in the bauxite. (b) The final stage is electrolysis. State the name of the material used as the cathode. Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 5

6 Write the ionic equation for the reaction that takes place at the cathode. (iii) Explain why the anode has to be replaced at regular intervals. (Total 10 mark) 6. (a) Poly(ethene) and poly(tetrafluoroethene), or PTFE, are widely-used polymers. Draw a representative length of the polymer chain for each of these polymers, making clear the repeating unit in each case. State why a polymer such as poly(ethene) does not have a sharp melting temperature, but softens over a range of temperature (b) Poly(tetrafluoroethene) is an expensive polymer, but is used in applications where extreme resistance to chemical attack is important. Suggest in terms of its bonding why PTFE is so inert. Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 6

7 (c) Herbicides such as 2,4-D and 2,4,5-T contain carbon-chlorine bonds. Explain why the strength of this bond is both an advantage and a disadvantage in the use of herbicides. (Total 9 marks) Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri 7

8 Edexcel-modelpaper-unit2-paper13 Jaydip.Chaudhuri Li Na K Rb Cs Fr (223) (226) (227) (261) (262) (263) 55 (99) (231) (147) (237) 150 (242) 152 (243) 157 (247) 159 (245) 163 (251) 165 (254) 167 (253) 169 (256) 173 (254) 175 (257) (210) (210) (222) Lithium Sodium Potassium Rubidium Caesium Francium Berylium Magnesium Calcium Strontium Barium Radium Scandium Yttrium Lanthanum Actinium Titanium Zirconium Hafnium Unnilquadium Vanadium Niobium Tantalum Unnilpentium Chromium Molybdenum Tungsten Unnilhexium Manganese Technetium Rhenium Cerium Thorium Praseodymium Protactinium Neodimium Uranium Promethium Neptunium Samarium Plutonium Europium Americium Gadolinium Curium Terbium Berkelium Dysprosium Californium Holmium Einsteinium Erbium Fermium Thulium Mendelevium Ytterbium Nobelium Lutetium Lawrencium Iron Ruthenium Osmium Cobalt Rhodium Iridium Nickel Palladium Platinum Copper Silver Gold Zinc Cadmium Mercury Boron Aluminium Gallium Indium Thallium Carbon Silicon Germanium Tin Lead Nitrogen Phosphorus Arsenic Antimony Bismuth Oxygen Sulphur Selenium Tellurium Polonium Fluorine Chlorine Bromine Iodine Astatine Neon Argon Krypton Xenon Radon Helium Hydrogen H Be Mg Ca Sr Ba Ra Sc Y La Ac Ti Zr Hf Unq V Nb Ta Unp Cr Mo W Unh Mn Tc Re Ce Th Pr Pa Nd U Pm Np Sm Pu Eu Am Gd Cm Tb Bk Dy Cf Ho Es Er Fm Tm Md Yb No Lu Lr Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg B Al Ga In Ti C Si Ge Sn Pb N P As Sb Bi O S Se Te Po F Cl Br I At Ne Ar Kr Xe Rn He Atomic Number Symbol Name Molar mass in g mol 1 eriod Key Group THE PERIODIC TABLE Lanthanide elements Actinide elements