0620_w19_qp_41
A paper of Chemistry, 0620
Questions:
7
Year:
2019
Paper:
4
Variant:
1
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1
This question is about ions and ionic compounds. Choose from the following list of ions to answer the questions. Br – Ca2+ Cl – Cr3+ Cu2+ K+ Li+ Na+ SO3 2– SO4 2– Each ion may be used once, more than once or not at all. State which ion: gives a lilac colour in a flame test forms a grey-green precipitate with aqueous ammonia forms a white precipitate with aqueous sodium hydroxide forms a cream precipitate with acidified aqueous silver nitrate forms a white precipitate with acidified aqueous barium nitrate. Describe how to do a flame test on a sample of a salt. Magnesiumphosphate contains magnesium ions, Mg2+, and phosphate ions, PO4 3–. Deduce the formula of magnesiumphosphate. 
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
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2
Sulfur exists as a number of different isotopes. What is meant by the term isotopes? A sulfide ion has the symbol shown. 34S 2– How many neutrons are contained in this sulfide ion? How is a sulfide ion, S2–, formed from a sulfur atom? Which element forms an ion with a 2+ charge that has the same number of electrons as a S2– ion? The manufacture of sulfuricacid by the Contact process occurs in four stages. stage 1 Molten sulfur is burned in air to produce sulfur dioxide gas. stage 2 Sulfurdioxide is reacted with oxygen to form sulfurtrioxide. stage 3 Sulfurtrioxide is combined with concentrated sulfuricacid to form oleum, H2S2O7. stage 4 Oleum is added to water to form sulfuricacid. Complete the chemical equation for stage1 by adding the appropriate state symbols. S( ) + O2( ) SO2( ) Name the catalyst used in stage2 and state the temperature used. catalyst temperature °C  Write chemical equations for the reactions in stage3 and stage4. stage3 stage4  Sulfurdioxide is a toxic gas. State one environmental reason why sulfur dioxide should not be released into the atmosphere. Describe the test for sulfurdioxide. test observations  Sulfurdioxide reacts with aqueous sodiumsulfite to produce a compound with the following composition by mass: 29.1% Na, 40.5% S and 30.4% O. Calculate the empirical formula of this compound.  empirical formula = 
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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3
This question is about metals and metal oxides. Most metals have a high melting point. State one other physical property that all metals have. Iron often rusts. Name the two substances, other than iron, that must be present for iron to rust.  Iron can be obtained by heating iron(oxide with zincpowder. Fe2O3 + 3Zn 2Fe + 3ZnO What can be deduced about the reactivity of zinc from this reaction? The ionic equation for this reaction is shown. 2Fe3+ + 3Zn 2Fe + 3Zn2+ Identify the oxidising agent in this reaction. Explain your answer in terms of electron transfer. oxidising agent explanation  Zincoxide is amphoteric. Describe two simple experiments to show that zinc oxide is amphoteric. Name the reagents you would use and describe the observations you would make. reagent 1 observation reagent 2 observation  
9. Metals  →  9.5. Corrosion of metals
9. Metals  →  9.4. Reactivity series
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4
Insoluble salts can be made by precipitation reactions. A student mixed solutions of some soluble salts. The results the student obtained are shown in the table. second salt solution Co(NO3)2AgNO3Pb(NO3)2first salt solution NaIno change yellow precipitate yellow precipitate Na2CO3purple precipitate yellow precipitate white precipitate Na2SO4no change white precipitate white precipitate All sodium salts are soluble in water. Use only results from the table to answer the following questions. Name: an insoluble cobalt salt an insoluble yellow lead salt. Write the chemical equation for the reaction in which silvercarbonate is formed. Write the ionic equation for the reaction in which lead(iodide is formed. Aqueous silvernitrate produces a yellow precipitate with both iodideions and carbonateions. When testing an unknown solution for iodideions, the aqueous silvernitrate is acidified. Explain why the aqueous silvernitrate is acidified. 
7. Acids, bases and salts  →  7.3. Preparation of salts
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5
Part of the structure of synthetic polymerA is shown. C CH3 CH3 CH3 CH3 C CH3 CH3 C CH3 CH3 C CH3 CH3 C CH3 CH3 C What type of synthetic polymer is A? Deduce the empirical formula of polymerA. Draw the structure of the monomer from which polymerA is made.  The formula C4H10 represents two different structural isomers. What is meant by the term structural isomers? Draw the structures of two structural isomers with the formula C4H10. Show all of the atoms and all of the bonds.  All structural isomers of C4H10 are flammable. Write a chemical equation for the incomplete combustion of C4H10. 
11. Organic chemistry  →  11.8. Polymers
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6
Dilute hydrochloricacid, HCl , reacts with aqueous sodiumcarbonate, Na2CO3. The chemical equation for the reaction is shown. 2HCl + Na2CO3 2NaCl + CO2 + H2O A 25.0 cm3 portion of Na2CO3was placed in a conical flask with a few drops of a suitable indicator. It was titrated against HCl of concentration 0.180 mol / dm3. 20.0 cm3 of HCl was required to reach the end-point. Calculate the concentration of the Na2CO3, in mol / dm3, using the following steps. ● ● Calculate the number of moles of HCl used in the titration.  mol ● ● Calculate the number of moles of Na2CO3 contained in the 25.0 cm3 portion of Na2CO3.  mol ● ● Calculate the concentration of the Na2CO3in mol / dm3.  mol / dm3  In another experiment, the volume of carbondioxide, CO2, produced was 48.0 cm3, measured at room temperature and pressure. How many moles of CO2 is this?  moles of CO2 = mol A sample of concentrated hydrobromic acid, HBr, was electrolysed using platinum electrodes. The concentration of the hydrobromic acid was 8.89 mol / dm3. Calculate the concentration of the HBrin g / dm3.  concentration of HBr= g / dm3 Explain why concentrated HBrcan conduct electricity. Magnesium is not a suitable material from which to make the electrodes. Explain why. Predict the product formed at the anode when concentrated HBris electrolysed. Write the ionic half-equation for the reaction occurring at the cathode. 
4. Electrochemistry  →  4.1. Electrolysis
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7
This question is about ethanol. Ethanol that is suitable for use as a fuel can be manufactured from sugars such as glucose, C6H12O6, by a two-step process. Describe how this can be done. In your answer, include: ● ● an equation for the reaction in which ethanol is formed ● ● the essential conditions for the reaction in which ethanol is formed ● ● the name of the process used to obtain ethanol that is pure enough to use as a fuel from the reaction mixture. The equation for the complete combustion of ethanol is shown. H C H H C H H O H O O + H O H + O C O Use the bond energies in the table to calculate the energy change, in kJ / mol, for the complete combustion of ethanol. bond bond energy in kJ / mol C–C C–H C–O C=O O–H O=O ● ● Energy needed to break bonds.  kJ ● ● Energy released when bonds are formed.  kJ ● ● Energy change for the complete combustion of ethanol.  energy change = kJ / mol  Ethanol can be oxidised by hydrogenperoxide to form ethanal, CH3CHO. A catalyst for this reaction is Fe3+. What is meant by the term catalyst ? The structure of ethanal is shown. H C H H C H O Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ethanal. Show outer shell electrons only. H H H H C C O  The table gives the boiling points of ethanal and ethanol. substance boiling point / °C ethanal ethanol In terms of attractive forces between particles, suggest why ethanal has a lower boiling point than ethanol. Ethene gas reacts with steam to form gaseous ethanol. C2H4+ H2OCH3CH2OHThe reaction can reach a position of equilibrium. The forward reaction is exothermic. State and explain the effect of increasing the pressure on the position of equilibrium. All other conditions are unchanged. Increasing the pressure of a gas increases its concentration. State and explain the effect of increasing the pressure on the rate of the reaction. All other conditions are unchanged. State and explain the effect of increasing the temperature on the position of equilibrium. All other conditions are unchanged. 
11. Organic chemistry  →  11.6. Alcohols
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