2022_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