0620_w13_qp_33
A paper of Chemistry, 0620
Questions:
6
Year:
2013
Paper:
3
Variant:
3
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1
For Examiner’s Use Zirconium (Zr) is a metal in Period 5. Its main oxidation state is +4. The following are all zirconium atoms: 90Zr , 91Zr and 92Zr . In terms of numbers of electrons, neutrons and protons, how are these three atoms the same and how are they different? They are the same because They are different because Containers for fuel rods in nuclear reactors are made of zirconium. Nuclear reactors are used to produce energy and to make radioactive isotopes. Which isotope of a different element is used as a fuel in nuclear reactors? State one medical and one industrial use of radioactive isotopes. Above 900 °C, zirconium reacts with water to form zirconium(oxide, ZrO2, and hydrogen. Write an equation for this reaction. In a nuclear accident, water may come in contact with very hot zirconium. Explain why the presence of hydrogen inside the reactor greatly increases the danger of the accident. It is possible to determine whether zirconium(oxide is acidic, neutral, basic or amphoteric using an acid and an alkali. Complete the table of possible results. If the oxide is predicted to react write ‘R’, if it is predicted not to react write ‘NR’. if the oxide is predicted result with hydrochloric acid predicted result with aqueous sodium hydroxide acidic neutral basic amphoteric
9. Metals  →  9.4. Reactivity series
6. Chemical reactions  →  6.4. Redox
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For Examiner’s Use The diagram shows the lattice of a typical ionic compound. – + – + – – + – + + – + – + – + + – – – + + + – Explain the term ionic lattice. In this lattice, the ratio of positive ions to negative ions is 1:1. In the lattice of a different ionic compound, the ratio of positive ions to negative ions is 1:2. Suggest why this ratio varies in different ionic compounds. Give three physical properties of ionic compounds. Strontium oxide is an ionic compound. Draw a diagram which shows its formula, the charges on the ions and the arrangement of the valency electrons around the negative ion. The electron distribution of a strontium atom is 2 + 8 + 18 + 8 + 2. Use o to represent an electron from a strontium atom. Use x to represent an electron from an oxygen atom.
2. Atoms, elements and compounds  →  2.4. Ions and ionic bonds
3. Stoichiometry  →  3.1. Formulae
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For Examiner’s Use The main uses of zinc are preventing steel from rusting and making alloys. The main ore of zinc is zinc blende. Zinc blende consists mainly of zinc sulfi de, ZnS. There are two major methods of extracting zinc from its ore. They are the direct reduction of zinc oxide to zinc and by electrolysis. In both methods, zinc oxide is made from the zinc sulfi de in the ore. How is zinc oxide made from zinc sulfi de? Write an equation for the reaction used to reduce zinc oxide to zinc. In the electrolytic method, zinc oxide reacts with sulfuric acid to form impure aqueous zinc sulfate. This solution contains Ni2+, Co2+ and Cu2+ ions as impurities. Write the equation for the reaction between zinc oxide and sulfuric acid. Nickel, cobalt and copper are all less reactive than zinc. Explain why the addition of zinc powder removes these ions from the solution. The solution of zinc sulfate is electrolysed using inert electrodes. This electrolysis is similar to that of copper(sulfate with inert electrodes. Write the equation for the reaction at the negative electrode . Complete the equation for the reaction at the positive electrode . OH– → 2H2O + + e– The electrolyte changes from zinc sulfate to For Examiner’s Use Brass is an alloy of copper and zinc. Suggest two reasons why brass is often used in preference to copper. Sacrifi cial protection is a method of rust prevention. Explain in terms of electron transfer why steel, which is in electrical contact with zinc, does not rust.
9. Metals  →  9.5. Corrosion of metals
9. Metals  →  9.4. Reactivity series
4. Electrochemistry  →  4.1. Electrolysis
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For Examiner’s Use Sulfuric acid is a strong acid. Hexanesulfonic acid is also a strong acid. It has similar properties to sulfuric acid. Sulfonic acids are made from alkanes and oleum, H2S2O7. C6H14 + H2S2O7 → C6H13SO3H + H2SO4 Describe how oleum is made from sulfur by the Contact process. Give equations and reaction conditions. How is concentrated sulfuric acid made from oleum? The formula of the hexanesulfonate ion is C6H13SO3 –. The formula of the barium ion is Ba2+. What is the formula of barium hexanesulfonate? Complete the following equations. magnesium + hexanesulfonic → + acid calcium + hexanesulfonic → + oxide acid C6H13SO3H + Na2CO3 → + + For Examiner’s Use Sulfuric acid is a strong acid. You are given aqueous sulfuric acid, concentration 0.1 mol / dm3, and aqueous hexanesulfonic acid, concentration 0.2 mol / dm3. Describe how you could show that hexanesulfonic acid is also a strong acid. Deduce why, for a fair comparison, the two acid solutions must have different concentrations. Explain the terms strong acid and weak acid.
7. Acids, bases and salts  →  7.1. The characteristic properties of acids and bases
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For Examiner’s Use Domestic rubbish is disposed of in landfi ll sites. Rubbish could include the following items. item of rubbish approximate time for item to break down newspaper one month cotton rag six months woollen glove one year aluminium container up to 500 years styrofoam cup 1000 years Explain why aluminium, a reactive metal, takes so long to corrode. Both paper and cotton are complex carbohydrates. They can be hydrolysed to simple sugars such as glucose. The formula of glucose can be represented as: HO OH Draw the structural formula of a complex carbohydrate, such as cotton. Include at least two glucose units. For Examiner’s Use Wool is a protein. It can be hydrolysed to a mixture of monomers by enzymes. What are enzymes? Name another substance which can hydrolyse proteins. What type of compound are the monomers formed by the hydrolysis of proteins? Which technique could be used to identify the individual monomers in the mixture? Proteins contain the amide linkage. Name a synthetic macromolecule which contains the same linkage. What is the scientifi c term used to describe polymers which do not break down in landfi ll sites? Styrofoam is poly. It is an addition polymer. Its structural formula is given below. Deduce the structural formula of the monomer, phenylethene. n CH2 CH C6H5
11. Organic chemistry  →  11.8. Polymers
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For Examiner’s Use The alcohols form a homologous series. The fi rst fi ve members are given in the table below. alcohol formula heat of combustion in kJ / mol methanol CH3OH ethanol CH3–CH2–OH propan-1-ol butan-1-ol CH3–CH2–CH2–CH2–OH pentan-1-ol CH3–CH2–CH2–CH2–CH2–OH Complete the table. Complete the equation for the combustion of pentan-1-ol in excess oxygen. C5H11OH + O2 → + State three characteristics of a homologous series other than the variation of physical properties down the series. The following alcohols are isomers. CH3–CH2–CH2–CH2–OH and (CH3)2CH–CH2–OH Explain why they are isomers. Draw the structural formula of another isomer of the above alcohols. For Examiner’s Use Alcohols can be made by fermentation and from petroleum. Ethanol is made from sugars by fermentation. C6H12O6 → 2C2H5OH + 2CO2 The mass of one mole of glucose, C6H12O6, is 180 g. Calculate the maximum mass of ethanol which could be obtained from 72 g of glucose. Describe how ethanol is made from petroleum. petroleum → ethene → ethanol
11. Organic chemistry  →  11.6. Alcohols
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