0620_s21_qp_43
A paper of Chemistry, 0620
Questions:
7
Year:
2021
Paper:
4
Variant:
3
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1
Give the name of the process that is used: to produce large molecules from monomers to separate oxygen from liquid air to make ethanol from glucose to separate water from aqueous sodiumchloride to produce aluminium from aluminiumoxide in molten cryolite to separate the products of hydrolysis of long chain carbohydrates to separate an aqueous solution from an undissolved solid. 
12. Experimental techniques and chemical analysis  →  12.4. Separation and purification
7. Acids, bases and salts  →  7.3. Preparation of salts
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3
Sodium reacts with fluorine to form sodiumfluoride, NaF. Write a chemical equation for this reaction. Sodiumfluoride is an ionic compound. Complete the diagram to show the electron arrangement in the outer shells of the ions present in sodiumfluoride. Give the charges on both ions. Na F  Aqueous sodiumfluoride undergoes electrolysis. State what is meant by the term electrolysis. Name the products formed at the positive electrode and the negative electrode when dilute aqueous sodiumfluoride undergoes electrolysis. anode cathode  Molten sodiumfluoride undergoes electrolysis. Name the products formed at the positive electrode and the negative electrode when molten sodiumfluoride undergoes electrolysis. anode cathode  Write the ionic half-equation for the reaction at the negative electrode . Complete the dot-and-cross diagram to show the electron arrangement in a molecule of fluorine, F2. Show the outer electrons only. F F  The melting points and boiling points of fluorine and sodiumfluoride are shown. melting point / °C boiling point / °C fluorine –220 –188 sodium fluoride Deduce the physical state of fluorine at –195 °C. Use the data in the table to explain your answer. physical state explanation  Explain, in terms of structure and bonding, why sodiumfluoride has a much higher melting point than fluorine. Your answer should refer to the: ● types of particle held together by the forces of attraction ● types of forces of attraction between particles ● relative strength of the forces of attraction. 
2. Atoms, elements and compounds  →  2.4. Ions and ionic bonds
4. Electrochemistry  →  4.1. Electrolysis
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4
Hydrogeniodide, HI, decomposes into iodine and hydrogen. The reaction is reversible. 2HII2+ H2colourless gas purple gas colourless gas A gas syringe containing a mixture of hydrogeniodide, iodine and hydrogen gases was sealed. After reaching equilibrium the mixture was a pale purple colour. end sealed plunger equilibrium mixture of hydrogen iodide, iodine and hydrogen State what is meant by the term equilibrium. The plunger of the gas syringe is pushed in. The position of equilibrium does not change. The colour of the gaseous mixture turns darker purple. The temperature remains constant. 2HII2+ H2colourless gas purple gas colourless gas Explain why the position of equilibrium does not change. Suggest why the colour of the gaseous mixture turns darker purple even though the position of equilibrium does not change. The forward reaction is endothermic. State what happens to the position of equilibrium when the temperature is decreased. State what happens to the rate of the forward reaction and the rate of the backward reaction when the temperature of the mixture is decreased. rate of the forward reaction rate of the backward reaction  
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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5
This question is about salts. Salts that are soluble in water can be made by the reaction between insoluble carbonates and dilute acids. Zincsulfate is soluble in water. You are provided with solid zinc carbonate, ZnCO3, and dilute sulfuric acid, H2SO4. Describe how you would make a pure sample of zincsulfate crystals. Your answer should include: ● practical details ● how you would make sure that all the dilute sulfuric acid has reacted ● a chemical equation for the reaction. Some sulfates decompose when heated. When hydrated iron(sulfate is heated strongly, sulfurdioxide gas is given off. Describe a test for sulfurdioxide. test observations  Complete the equation for the decomposition of hydrated iron(sulfate. FeSO4•7H2O → Fe2O3 + SO2 + SO3 + H2O Some chlorides are hydrated. When hydrated bariumchloride crystals, BaCl 2•xH2O, are heated they give off water. BaCl 2•xH2O→ BaCl 2+ xH2OA student carries out an experiment to determine the value of x in BaCl 2•xH2O. step 1 Hydrated bariumchloride crystals are weighed. step 2 The hydrated bariumchloride crystals are then heated. step 3 The remaining solid is weighed. Describe how the student can be sure that all the water is given off. In an experiment, 4.88 g of BaCl 2•xH2O is heated until all the water is given off. The mass of BaCl 2 remaining is 4.16 g. [Mr: BaCl 2, 208; H2O, 18] Determine the value of x using the following steps. ● Calculate the number of moles of BaCl 2 remaining.  mol ● Calculate the mass of H2O given off.  g ● Calculate the number of moles of H2O given off.  mol ● Determine the value of x.  x =  
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
7. Acids, bases and salts  →  7.3. Preparation of salts
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6
This question is about metals. Iron is extracted from its main ore in a blast furnace. waste gases slag air air A Coke and iron ore are added at the top of the blast furnace. Name one other substance that is added at the top of the blast furnace. Name the substance that leaves the blast furnace at A. Iron ore is mainly iron(oxide, Fe2O3. Name a substance that reduces iron(oxide to iron in the blast furnace. Temperatures inside a blast furnace can reach 2000 °C. Name two substances that react together, in the blast furnace, to produce this high temperature. Name two waste gases that leave the blast furnace.  Zinc is extracted from zinc blende. Name the main zinc compound that is present in zinc blende. When zinc is extracted, it is formed as a gas. The gaseous zinc is then converted into molten zinc. State the name of this physical change. Name the alloy that contains zinc and copper only. Copper has the following properties. ● It has a high melting point. ● It has a high density. ● It is a good conductor of electricity. ● It has variable oxidation states. ● It forms a basic oxide. ● It forms soluble salts. Give two properties from the list in which copper differs from GroupI elements.  Give two properties from the list in which copper is similar to GroupI elements.  
9. Metals  →  9.4. Reactivity series
9. Metals  →  9.6. Extraction of metals
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7
Many organic compounds contain carbon, hydrogen and oxygen only. An organic compound R has the following composition by mass. C, 69.77%; H, 11.63%; O, 18.60% Calculate the empirical formula of compound R.  empirical formula = Compound S has the empirical formula CH2O and a relative molecular mass of 60. Calculate the molecular formula of compound S.  molecular formula = Compounds T and V have the same molecular formula, C3H6O2. ● Compound T is an ester. ● Compound V contains a –COOH functional group. State the name given to compounds with the same molecular formula but different structures. Name the homologous series that V is a member of. Draw a structure of compound T. Show all of the atoms and all of the bonds. Name compound T. name  Draw the structure of compound V. Show all of the atoms and all of the bonds. Name compound V. name  Ethanol can be produced from long chain alkanes such as decane, C10H22, in a two-step process. step 1 step 2 decane ethene ethanol For each of the two steps: ● name the type of chemical reaction that occurs ● write a chemical equation. step 1: decane to ethene type of reaction chemical equation step 2: ethene to ethanol type of reaction chemical equation  
11. Organic chemistry  →  11.2. Naming organic compounds
11. Organic chemistry  →  11.1. Formulae, functional groups and terminology
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