2022 MGS TPaper 3 Planning Questions Part 2

Page 1 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) Name : _______________________( ) Date: _________ Class: Sec 4 ( ) Practice on Planning Questions 1 A white solid mixture contains mainly zinc sulfate with lead(II) sulfate as an impurity. Plan an experiment to find out the percentage purity of the zinc sulfate in the mixture. You should include details of the method and any apparatus used. 2 Malachite is a naturally occurring form of copper(II) carbonate. Outline how a sample of the metal can be obtained from large lumps of malachite in the laboratory. Copper is one of the least reactive metals. Your answer should include any chemicals used and conditions. Jun 2010 1. Weigh the mixture of white solids using an electronic weighing balance. Record its mass. 2. Add excess water to the mixture and stir to dissolve the zinc sulfate. 3. Filter the mixture to obtain insoluble lead(II) sulfate as the residue. 4. Wash the residue with a little amount of distilled water. 5. Dry the residue between pieces of filter paper. 6. Weigh the pure, dry lead(II) sulfate. Record the mass. Results Subtract the mass of lead(II) sulfate from the mass of impure mixture to find the mass of pure dry zinc sulfate. % purity of ZnSO4 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑢𝑟𝑒 𝑧𝑖𝑛𝑐 𝑠𝑢𝑙𝑓𝑎𝑡𝑒 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑖𝑚𝑝𝑢𝑟𝑒 𝑧𝑖𝑛𝑐 𝑠𝑢𝑙𝑓𝑎𝑡𝑒 x 100% Note: Alternatively, use the filtrate (zinc sulfate solution) and perform crystallisation (4 steps – Here Comes Fat Donkey) Heat the solution until it is saturated. Cool the hot solution. Filter out the mixture. Dry the crystals between pieces of filter paper. (Do not wash because zinc sulfate is a soluble salt) CuCO3 → CuO + CO2 CuO + C → Cu + CO2

Page 2 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) 3 Petrol is a liquid fuel obtained from petroleum (crude oil). Bioethanol is a liquid fuel made from the fermentation of carbohydrates obtained from plants such as sugar cane. Plan an experiment to investigate which of these two fuels produces more energy. You may draw a picture to help you answer the question. Jun 2011 1. Set up the apparatus as shown in the diagram below. 2. Weigh a fixed mass of petrol using an electronic weighing balance. 3. Measure 50 cm3 (or fixed volume) of water using a measuring cylinder and pour it into a beaker. 4. Use a thermometer to measure the initial temperature of the water. 5. Burn the petrol and use the flame to heat up the water. 6. Measure the final temperature of the water when all the petrol is burnt away. 7. Find the temperature change in the water. 8. Repeat the experiment with the same mass of bioethanol and same volume of water. The fuel that gives the larger rise in temperature of the water produces more heat energy. Note: You cannot burn petrol or bioethanol directly and measure the temperature of the petrol/bioethanol because they are flammable.

Page 3 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) 4 Solutions of chemicals known as corrosion inhibitors are added to the water in steel radiators to reduce rust. You are provided with three different bottles of liquid corrosion inhibitors R, S and T and some steel nails. Plan an experiment to investigate if these inhibitors prevent the corrosion of steel a nd which of these inhibitors is the most effective. Jun 2012 5 Iron rusts when in contact with air and water. You are provided with iron nails and t hree different samples of water, tap water, sea water and distilled water. Plan an investigation to find out which sample of water causes iron to rust the fastest. Nov 2010

Page 4 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) 6 Seawater contains sodium chloride and other salts. Plan an experiment to find the mass of salts in 1 dm3 of seawater. You will be provided with a small bottle of seawater. You should include details of the method and any apparatus used. Nov 2011

Page 5 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) 7 Kleen Up is a colourless liquid used to clean work surfaces and glass windows. Kleen Up contains ammonia solution which is a weak alkali. Plan an experiment to determine the concentration of ammonia in Kleen Up. You are provided with aqueous nitric acid of known concentration and common laboratory apparatus. Nov 2011 8 Calcium carbonate is found in limestone and marble. All carbonate s react with hydrochloric acid to from chlorides. Calcium carbonate is insoluble in water but calcium chloride is soluble in water. Most impurities in limestone and marble are insoluble. Plan an experiment to find out whether limestone or marble contain more insoluble impurities. You are provided with common laboratory apparatus. Nov 2012

Page 6 of 6 Methodist Girls’ School Chemistry Sec 4 (2020) 9 Coal is a fossil fuel. When heated strongly, sulfur dioxide gas is one of the products formed. Sulfur dioxide changes aqueous acidified potassium manganate(VII) from purple to colourless. Plan an investigation to show which of two different types of coal produces more sulfur dioxide gas when heated. Nov 2012 10 You are provided with 2 bottles of white solids whose label has fallen off. One bottle contains sodium carbonate and another contains sodium hydrogencarbonate. Plan an investigation to identify the 2 white solids. Concept : 2NaHCO3 → Na2CO3 + H2O + CO2 Na2CO3 is a stable carbonate and cannot decompose on heating. Use of acid will not work because both carbonates will give carbon dioxide. NaHCO3 + HCl → NaCl + CO2 + H2O Na2CO3 + 2HCl → 2NaCl + CO2 + H2O *Heating of metal carbonates/hydrogencarbonates produces the same products. Heating of metal hydrogen carbonates does not give hydrogen gas. There are only 3 ways to produce hydrogen in the laboratory besides electrolysis of water or cracking of oil. Metal + water/steam/acid Place a spatulaful of white solid and put it in a dry test-tube. Set up the apparatus as shown in the diagram. Heat the test-tube of solid using a Bunsen burner and observe if white precipitate is observed in the test-tube containing limewater. If white precipitate is observed, then the test-tube contains sodium hydrogen carbonate. If no precipitate is observed in the limewater, then it must be Calcium carbonate.

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