0620_w10_qp_33
A paper of Chemistry, 0620
Questions:
7
Year:
2010
Paper:
3
Variant:
3
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1
For Examiner’s Use The diagrams below show the electron arrangement in two compounds. K + – H H O Cl In a water molecule, each hydrogen atom is bonded to the oxygen atom by sharing a pair of electrons. Why does an oxygen atom share two pairs of electrons rather than just one pair? Describe how a potassium atom becomes a potassium ion. Why is there a bond between the ions in potassium chloride? Solid potassium chloride is a poor conductor of electricity. When dissolved in water it is a good conductor. Explain.
2. Atoms, elements and compounds  →  2.4. Ions and ionic bonds
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2
For Examiner’s Use Vanadium is a transition element. An atom of the most common isotope of vanadium can be represented as . Complete the following table to show the number of protons, electrons and neutrons in each particle. particle number of protons number of electrons number of neutrons V V 3+ V The major use of vanadium is to make vanadium steel alloys. Explain the phrase steel alloys. State the name and use of another steel alloy. name use Two of the oxidation states of vanadium are +3 and +4. Write the formula of vanadium(oxide and of vanadium(oxide. vanadium(oxide vanadium(oxide Vanadium(oxide is basic and vandium(oxide is amphoteric. Describe how you would obtain a sample of vanadium(oxide from a mixture of these two oxides. V
9. Metals  →  9.3. Alloys and their properties
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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3
For Examiner’s Use The reactions of a metal and the thermal stability of some of its compounds are determined by the position of the metal in the reactivity series. To fi nd the order of reactivity of the metals, cobalt, magnesium, silver and tin, the following experiments were carried out. experiment result tin plus silver(nitrate solution silvery layer on tin magnesium plus tin(nitrate solution grey deposit on magnesium tin plus cobalt nitrate solution no reaction Give as far as possible the order of reactivity of these metals. Write the least reactive fi rst. What additional experiment needs to be done to put all four metals in order of reactivity? Write an ionic equation for the reaction between tin atoms and silver(ions. Indicate on the equation the change which is oxidation. Sodium is a more reactive metal than magnesium. Sodium compounds are more stable than magnesium compounds. In an experiment, their hydroxides were heated. If the hydroxide did not decompose write ‘no reaction’ otherwise complete the equation. NaOH → Mg(OH)2 → For Examiner’s Use A cell consists of two different metal electrodes in an electrolyte. Three possible cells are shown below. V zinc copper dilute acid 1.1 V V tin dilute acid 0.5 V V zinc tin dilute acid V + – + – Why is the more reactive metal the negative electrode? How can you deduce that zinc is more reactive than tin? How could you change the zinc/copper cell to have a voltage greater than 1.1 V? Complete the labelling of the zinc/tin cell.
9. Metals  →  9.4. Reactivity series
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4
For Examiner’s Use The electrolysis of concentrated aqueous sodium chloride, between inert electrodes, is used to make four important chemicals. hydrogen chlorine sodium hydroxide sodium chlorate(The ions present in the electrolyte are Na+, H+, Cl – and OH –. Hydrogen ions are discharged at the negative electrode . Write an equation for this reaction. The hydrogen ions are from the water. H2O H+ + OH – Suggest an explanation why the concentration of hydroxide ions increases. When a dilute solution of sodium chloride is used, chlorine is not formed at the positive electrode , a different gas is produced. Name this gas. State an example of an inert electrode. State a use of hydrogen. Why is chlorine used to treat the water supply? For Examiner’s Use Sodium chlorate(is made by the reaction between chlorine and sodium hydroxide. It is used as bleach but over time it decomposes. 2NaCl O→ 2NaCl + O2The rate of decomposition can be studied using the apparatus shown below. sodium chlorate(solution How could you measure the rate of decomposition of sodium chlorate(? Describe how you could show that the rate of decomposition of sodium chlorate(is a photochemical reaction.
4. Electrochemistry  →  4.1. Electrolysis
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5
For Examiner’s Use Carboxylic acids contain the group O O H C or COOH. Ethanoic acid is a typical carboxylic acid. It forms ethanoates. Complete the following equations. Mg + CH3COOH → + ethanoic acid sodium hydroxide + → + Ethanoic acid reacts with ethanol to form an ester. Give the name of the ester and draw its structural formula. Show all of the bonds. name structural formula Maleic acid is an unsaturated acid. 5.8 g of this acid contained 2.4 g of carbon, 0.2 g of hydrogen and 3.2 g of oxygen. How do you know that the acid contained only carbon, hydrogen and oxygen? Calculate the empirical formula of maleic acid. Number of moles of carbon atoms = Number of moles of hydrogen atoms = Number of moles of oxygen atoms = The empirical formula is For Examiner’s Use The mass of one mole of maleic acid is 116 g. What is its molecular formula? Maleic acid is dibasic. One mole of acid produces two moles of H+. Deduce its structural formula.
11. Organic chemistry  →  11.7. Carboxylic acids
7. Acids, bases and salts  →  7.1. The characteristic properties of acids and bases
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6
For Examiner’s Use The Kinetic Theory explains the properties of matter in terms of the arrangement and movement of particles. Nitrogen is a gas at room temperature. Nitrogen molecules, N2, which are spread far apart move in a random manner at high speed. Draw a diagram showing the arrangement of the valency electrons in a nitrogen molecule. Use × to represent an electron from a nitrogen atom. How does the movement and arrangement of the molecules in a crystal of nitrogen differ from those in gaseous nitrogen? Use the ideas of the Kinetic Theory to explain the following. A sealed container contains nitrogen gas. The pressure of a gas is due to the molecules of the gas hitting the walls of the container. Explain why the pressure inside the container increases when the temperature is increased. For Examiner’s Use The following apparatus can be used to measure the rate of diffusion of a gas. constant pressure applied gas syringe gas metal foil gas escapes through small hole in foil The following results were obtained. gas temperature / °C rate of diffusion in cm3 / min nitrogen 1.00 chlorine 0.63 nitrogen 1.05 Explain why nitrogen diffuses faster than chlorine. Explain why the nitrogen diffuses faster at the higher temperature.
1. States of matter  →  1.2. Diffusion
1. States of matter  →  1.1. Solids, liquids and gases
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7
For Examiner’s Use Synthetic polymers are widely used in the modern world. Their use has brought considerable advantages to modern life as well as some disadvantages. Suggest two advantages of a plastic bucket compared to a steel bucket. Name two uses of man-made fi bres, such as nylon and Terylene. Describe the pollution caused by synthetic polymers. One type of polymer is formed by addition polymerisation. The structural formula of an addition polymer is given below. n CH CH3 CH2 Give the name and structural formula of the monomer. name of monomer structural formula of monomer For Examiner’s Use Draw the structural formula of the addition polymer formed by the polymerisation of phenylethene. The structural formula of phenylethene is given below. C C H H C6H5 H Nylon is made by condensation polymerisation. It has the structural formula shown below. C (CH2)8 (CH2)6 O O C N H N H Name the linkage in this polymer. Name the natural macromolecules which have the same linkage. Deduce the formulae of the two monomers which reacted to form the nylon and water. monomer monomer
11. Organic chemistry  →  11.8. Polymers
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