ST. FRANCIS SECONDARY SCHOOL HALF YEARLY EXAMINATION SPECIMEN PAPER FORM 4 CHEMISTRY TIME: 2 HOURS Name: Total Mark from 90: A copy of the periodic table is provided during the exam. You are reminded of the necessity for good English and orderly presentation in your answers. In calculations you are advised to show all the steps in your working. Electronic Calculators may be used in any part of the examination. Useful Data: Relative Atomic Masses may be taken: Hydrogen (H) = 1.0 Sodium (Na) = 23.0 Oxygen (O) = 16.0 Copper (Cu) = 64.0 Sulfur (S) = 32.0 Chlorine (Cl) = 35.5 Calcium (Ca) = 40.0 Carbon (C) = 12.0 Avogadro s Constant = 6 x 10 23 One mole of any gas occupies 22,400cm 3 or 22.4L (dm 3 ) at Standard temperature and pressure (S.T.P) STP conditions are to be taken as 0 C and 760mmHg
Section A: Answer ALL Questions in this section using the space provided. This section carries 50 marks. This question is about Thermal Decomposition (Total: 8 marks) Three carbonate compounds; sodium carbonate, zinc carbonate and copper carbonate, are heated one at a time in the apparatus as shown below: Complete the following table for the above reactions. Metal Carbonate Colour before heating Colour after heating Gas produced (if any) Sodium carbonate White Zinc carbonate White Copper carbonate Green (6 marks)
Write down balanced equations including state symbols for the thermal decomposition of zinc carbonate and copper carbonate. Zinc Carbonate: Copper Carbonate: This question is about Group 1 Metals and Moles (Total: 8 marks) The equation below shows the reaction of sodium with water. In an experiment 0.85g of sodium were reacted with a large volume of water. 2Na (s) + 2H 2 O (l) 2NaOH (aq) + H 2 (aq) Find the number of moles of sodium reacting with water in this experiment. (1 mark) Determine the number of moles of hydrogen produced during this reaction (1 mark)
Using your answer in question (b) calculate the volume of hydrogen produced at S.T.P. What mass of sodium is required to produce 1.8 dm 3 of hydrogen at S.T.P.? Comment on the safety of using a piece of sodium of this mass obtained in (d) in reaction with water.
(1 mark) Sodium hydroxide is also called soda lime, mention one way in which soda lime is used in industry. (1 mark) This question is about Moles (Total: 9 marks) When hydrated copper sulfate (CuSO 4. x H 2 O) is strongly heated in a boiling tube, the change taking place can be represented by: CuSO 4. x H 2 O (s) CuSO 4 (s) + xh 2 O (aq) Describe what you would observe when hydrated copper sulfate is heated.
When a sample of hydrated copper sulfate was heated to a constant mass to yield the anhydrous copper sulfate the following data was obtained: Mass of crucible and lid = 21.00g Mass of crucible and lid and hydrated copper sulfate = 25.98g Mass of crucible and lid and copper sulfate after heating = 24.18g Calculate the mass of one mole of anhydrous copper sulfate. (1 mark) Calculate the number of moles of CuSO 4 present after heating the sample. Find the mass of water of crystallisation lost by the sample of hydrated copper sulfate and hence calculate the number of moles of crystallisation lost by the sample.
Use your answers obtained in part (ii). And (iii). to find the value of x in the formula CuSO 4.xH 2 O. This question is about Group 1 and 2 Metals (Total: 7 marks) Give similarities and differences in the reactions of: Sodium and potassium with water sodium and calcium with water
Give two general similarities between Group 1 and Group 2 elements. State one use of magnesium hydroxide. (1 marks) This question is about Gases in Air (Total: 10 marks) Complete the following: Air is a mixture of gases which can be separated by. The most abundant gas in air is. is the most reactive gas in air, while the are very unreactive. Air also contains a very small percentage of and. (6 marks) Describe an experiment that demonstrates the essential conditions required for iron to rust. Show your answer with a diagram. (4 marks)
This question is about Ionic Equations (Total: 8 marks) Write a balanced ionic equations: omitting spectator ions and including state symbols for the reactions between: Barium (II) Chloride + Dilute Sulfuric Acid Sodium Carbonate + Dilute Sulfuric Acid (2 Marks) Aqueous Sodium Sulfite + Dilute Hydrochloric Acid (2 Marks) (2 Marks)
Aqueous Ammonium Sulfate + Sodium hydroxide Section B: Answer TWO Questions from this section on separate sheets. Each Question carries 20 marks. (2 Marks) This question is about Volumetric Analysis (Total: 20 marks) The following results were obtained on titrating 25 cm 3 of a solution of sodium carbonate with a 0.025 mol/dm 3 solution of hydrochloric acid. 1 2 3 Final Burette Reading/cm 3 22.05 22.20 22.35 Initial Burette Reading/cm 3 0.00 0.10 0.20 Volume of Acid used/cm 3 22.05 22.10 22.15 Write a balanced equation for the reaction of sodium carbonate with hydrochloric acid. Calculate the average titre value. (Show your working) Using the average titre value calculate the number of moles of hydrochloric acid involved in this titration.
Determine the number of moles of sodium carbonate reacting with the hydrochloric acid and hence find its molar concentration. (8 marks) A solution of sodium carbonate is often used in titration experiments as a standard solution. Explain what is meant by the term standard solution. Using well labelled diagrams show how you would prepare a standard solution of sodium carbonate. (7 marks) Describe the titration procedure, including any practical steps which must be taken to obtain accurate titration values. (Your answer must include a labelled diagram) (5 marks) This question is about Oxygen (Total: 20 marks) Oxygen can be prepared in the laboratory by the catalytic decomposition of hydrogen peroxide. 2H 2 O 2 (aq) 2H 2 O (l) + O 2 (g) Draw and label a diagram of the apparatus you would use in order to prepare oxygen by this method. (5 marks) Name and give the formula of the catalyst used in this reaction.
What volume of oxygen, measured at S.T.P. can be obtained from the complete decomposition of 200cm 3 of hydrogen peroxide of concentration 2 mol/dm 3? (5 marks) State briefly how oxygen can be prepared on a large scale industrially and mention two uses of the gas. (3 marks) How would you test for the presence of oxygen? Name three methods how oxygen and water can be prevented from coming into contact with iron to prevent rust formation. (3 marks) This question is about Moles (Total: 20 marks) Calculate the number of moles of HCl in each of the following:
A pressurised cylinder containing 7.30g of liquid hydrogen chloride (3 marks) 250cm 3 of a solution of hydrochloric acid of concentration 0.75 mol/dm 3. (3 marks) 10.0 dm 3 of gaseous hydrogen chloride measured at a pressure of 1.5 atm. and a temperature of 91 C. (Hint: You have to use the general gas equation first!) (6 marks) What volume of hydrochloric acid of concentration 0.75 mol/dm 3 is required to react exactly with 1.00g of pure calcium carbonate? (Hint: Write the equation for the reaction first!) (8 marks) THE END GOOD LUCK! ;)