1 KIDS CAMPUS SCHOOL (SENIOR SECTION) PRE-MOCK EXAM-1 SESSION 2022 – 2023 GRADE 10 SUBJECT: CHEMISTRY TIME: 1 Hour 15 Minutes 0620/42 FULL MARKS: 80 CANDIDATE NAME CENTRE NUMBER CANDIDATE NUMBER Invigilator’s Signature___________ Examiner’s Signature___________ Marks Obtained____ Paper 4 IGCSE Structured Questions Candidates must answer on the Question Paper No additional materials are required INSTRUCTIONS • Answer all questions. • Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. • Write your name, center number and candidate number in the boxes at the top of the page. • • • • Write your answer to each question in the space provided. Do not use an erasable pen or correction fluid. You may use a calculator. You should show all your working and use appropriate units. INFORMATION • The total mark for this paper is 80. • The number of marks for each question or part question is shown in brackets [ ]. This document has 12 pages. Any blank pages are indicated. 1 1 Part of a synthetic polymer is shown. C 2H 5 H C2H5 H C C C C H H H H (a) State the number of monomer units that are needed to make the part of the polymer shown. ........................................................................................................................................... [1] (b) Name and draw the structure of the monomer used to make this polymer. Show all of the atoms and all of the bonds. structure name ............................................................ [3] (c) State the empirical formula of the polymer. ........................................................................................................................................... [1] [Total: 5] 2 Proteins are natural polymers. Proteins contain amide linkages. Synthetic polyamides also contain amide linkages. (a) Name a synthetic polyamide. ........................................................................................................................................... [1] (b) Identify the two functional groups present in the monomers used to produce synthetic polyamides. 1 ........................................................................................................................................ 2 ........................................................................................................................................ [2] [Total: 3] 2 3 Aqueous ethanoic acid has chemical properties which are typical of acids. Describe two chemical properties of aqueous ethanoic acid. 1 ............................................................................................................................................... .................................................................................................................................................. 2 ............................................................................................................................................... .................................................................................................................................................. [2] [Total: 2] 4 The table compares the time taken for reaction of an alloy with ethanoic acid, nitric acid and phosphoric acid, each at three different concentrations. The time taken for the alloy to decrease in mass by 1.0 g was measured. All other conditions were kept the same. (a) How does the concentration of acid affect the rate of reaction? ........................................................................................................................................... ........................................................................................................................................... [1] (b) Which acid reacts most rapidly with the alloy? ........................................................................................................................................... [1] (c) Predict how long it would take for the alloy to decrease in mass by 1.0 g using phosphoric acid 3 of concentration 0.03 mol / dm . time taken = ........................... hours [1] 3 (d) Suggest which one of these pH values is the pH of concentrated aqueous ethanoic acid. Draw a circle around the correct answer. pH 4 pH 7 pH 10 pH 13 [1] [Total: 4] 5 Ester Y has the structure shown. O H C H O C H H (a) Ester Y can be made by reacting two organic compounds together. Name the compounds and draw their structures. Show all of the atoms and all of the bonds. (i) structure name ..................................................................................................................... [2] (ii) structure name ..................................................................................................................... [2] [Total: 4] 6 Molecules A and B can form condensation polymers. 4 A HO B OH HOOC COOH (a) Each molecule has two identical functional groups. (i) Name the functional group in B. ................................................................................................................................ [1] (ii) Draw the part of the structure of the synthetic polymer that would form when two molecules of A and two molecules of B combine. Show all of the bonds in the linkages. [3] (iii) Name the other product formed when molecules of A and B undergo polymerisation. ................................................................................................................................ [1] (b) Molecule A is a simple sugar unit which can be made by hydrolysis of complex carbohydrates. (i) Draw part of the complex carbohydrate that could be hydrolysed to make molecules of A. Include one linkage and show all of the bonds in the linkage. [1] (ii) State two sets of conditions which could be used to hydrolyse the complex carbohydrates to form A. 1 ........................................................................................................................... 2 ........................................................................................................................... [2] (iii) Name the technique used to identify the individual sugar units made by the hydrolysis of a complex carbohydrate. ................................................................................................................................ [1] [Total: 9] 7 Titanium is extracted from an ore called rutile. Rutile is an impure form of titanium(IV) oxide, TiO2. 5 Rutile is mixed with coke and heated in a furnace through which chlorine gas is passed. The product is gaseous titanium(IV) chloride, TiCl4. Titanium(IV) chloride, TiCl4, is heated with an excess of magnesium, in an atmosphere of argon. After titanium(IV) chloride is heated with magnesium, the unreacted magnesium is removed by adding an excess of dilute hydrochloric acid to the mixture. The dilute hydrochloric acid also dissolves the magnesium chloride. The dilute hydrochloric acid does not react with the titanium or dissolve it. (a) Give two observations and write a chemical equation for the reaction that occurs when dilute hydrochloric acid reacts with magnesium. 1 ........................................................................................................................................ 2 ........................................................................................................................................ chemical equation ............................................................................................................. [3] (b) Name the process that is used to separate the titanium from the mixture after all the magnesium has been removed. ........................................................................................................................................... [1] (c) Titanium does not react with the dilute hydrochloric acid or dissolve in it. Suggest why titanium does not react with dilute hydrochloric acid. ........................................................................................................................................... [1] [Total: 5] 8 A list of techniques used to separate mixtures is given below. chromatography evaporation filtration crystallisation diffusion fractional distillation dissolving simple distillation (a) From the list, choose the most suitable technique to separate the following. water from sea-water ...................................................................................................... helium from a mixture of helium and methane ................................................................ ethanol from a mixture of ethanol and propanol ............................................................. iron filings from a mixture of iron filings and water .......................................................... a mixture of two amino acids, glycine and alanine .......................................................... [5] 6 (b) Describe how you would obtain a pure sample of copper(II) sulfate-5-water crystals from a mixture of copper(II) sulfate-5-water with copper(II) oxide using some of the techniques listed above. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [4] [Total: 9] 9 Sodium burns in air to form sodium oxide, Na2O. (a) State the colour of the flame seen when sodium burns. ........................................................................................................................................... [1] (b) Write a chemical equation for the reaction which takes place when sodium burns in air to form sodium oxide. ........................................................................................................................................... [2] [Total: 3] 10 Sodium reacts vigorously with water to form aqueous sodium hydroxide, NaOH, which is a strong base. The equation for the reaction is shown. 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) 3 Calculate the concentration of NaOH(aq) formed, in g / dm , when 0.345 g of sodium is added to 3 50.0 cm of distilled water. Assume there is no change in volume. Use the following steps. (a) Calculate the number of moles of Na added. = ............................... mol [1] 7 (b) Determine the number of moles of NaOH formed. = ............................... mol [1] 3 (c) Calculate the concentration of NaOH in mol / dm . 3 [1] 3 [2] concentration of NaOH = .......................... mol / dm 3 (d) Determine the Mr of NaOH and calculate the concentration of NaOH in g / dm . concentration of NaOH = .............................. g / dm [Total: 5] 11 Dilute sulfuric acid is electrolysed using the apparatus shown in the diagram. power supply + – inert electrodes dilute sulfuric acid (a) State what is meant by the term electrolysis. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [2] 8 (b) Explain why inert electrodes are used. ........................................................................................................................................... ........................................................................................................................................... [1] (c) Name the products formed at each electrode. negative electrode ........................................................................................................... positive electrode ............................................................................................................ [2] (d) Write an ionic half-equation for the reaction at the negative electrode. ........................................................................................................................................... [2] [Total: 7] 12 Chlorine reacts with carbon monoxide to produce phosgene gas, COCl2(g). A catalyst is used. Cl2(g) + CO(g) ⇌ COCl2(g) The reaction is exothermic. (a) Explain why the reaction is exothermic in terms of the energy changes of bond breaking and bond making. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... (b) [3] 9 (i) Complete the energy level diagram for this reaction. On your diagram show: • the product of the reaction • an arrow representing the energy change, labelled ΔH • an arrow representing the activation energy, labelled ΔA. energy [3] Cl 2(g) + CO(g) progress of reaction [3] (ii) State why a catalyst is used. ................................................................................................................................ [1] [Total: 7] 13 Ethanoic acid is manufactured by the reaction of methanol with carbon monoxide. An equilibrium mixture is produced. CH3OH(g) + CO(g) ⇌ CH3COOH(g) (a) State two characteristics of an equilibrium. 1 ...................................................................................................................................... 2 ...................................................................................................................................... [2] 10 (b) The purpose of the industrial process is to produce a high yield of ethanoic acid at a high rate of reaction. The manufacture is carried out at a temperature of 300 °C. The forward reaction is exothermic. Use this information to state why the manufacture is not carried out at temperatures: • below 300 °C ........................................................................................................................................... • above 300 °C ........................................................................................................................................... [2] (c) Complete the table using only the words increases, decreases or no change. effect on the rate of the forward reaction effect on the equilibrium yield of CH3COOH(g) adding a catalyst no change decreasing the pressure [3] (d) Suggest which of the following metals is a suitable catalyst for the reaction. Give a reason for your answer. aluminium calcium cobalt magnesium potassium suitable catalyst .............................................................................................................. reason ............................................................................................................................. [2] [Total: 9] 14 A student prepares magnesium sulfate crystals, MgSO4, by adding excess magnesium to dilute sulfuric acid. Describe two observations which show the reaction has finished. 1 ............................................................................................................................................... 2 ............................................................................................................................................... [2] [Total: 2] 15 Electrolysis is carried out on aluminium oxide dissolved in molten cryolite. 11 waste gases positive electrode negative electrode aluminium oxide dissolved in molten cryolite aluminium (a) Give two reasons why the electrolysis is carried out on aluminium oxide dissolved in molten cryolite instead of electrolysing molten aluminium oxide only. 1 ........................................................................................................................................ 2 ........................................................................................................................................ [2] (b) Write the ionic half-equation for the reaction occurring at the negative electrode. ........................................................................................................................................... [2] (c) The positive electrodes are made of carbon. Explain why the positive carbon electrodes are replaced regularly. ........................................................................................................................................... ........................................................................................................................................... [2] [Total: 6]
