12. Experimental techniques and chemical analysis
A section of Chemistry, 0620
Listing 10 of 677 questions
Use The diagram shows the salt mines at Bex in Switzerland. salt solution pumped up mountain side underground reservoir sodium chloride solution rock (mainly anhydrite) layers of salt air vent The salt is dissolved by water from underground springs and then pumped up to a reservoir where it is stored as a solution. Write the chemical formula for sodium chloride. Suggest how solid sodium chloride is obtained from the sodium chloride solution. Examiner's Use Sodium chloride has an ionic giant structure. Which one of the following best describes an aqueous solution of sodium chloride? Tick one box. a mixture of sodium ions and chlorine molecules in water a mixture of sodium and chlorine atoms in water a mixture of sodium and chloride ions in water a mixture of sodium, chloride, oxide and hydrogen ions Describe a test for chloride ions. test result The rock surrounding the layers of salt is anhydrite. Pure anhydrite has the chemical formula CaSO4. State the name of the chemical found in anhydrite. Calculate the relative formula mass of the chemical in pure anhydrite. When anhydrite reacts with water, gypsum (CaSO4.2H2O) is formed. Complete the equation for this reaction. CaSO4 + CaSO4.2H2O Which one of the following describes this reaction? Put a ring around the correct answer. combustion fermentation hydration oxidation reduction Examiner's Use The chemical in anhydrite can be made by reacting calcium hydroxide with sulphuric acid. Complete the balanced equation for this reaction. Ca(OH)2 + CaSO4 + H2O The spring water running through the rocks changes anhydrite into gypsum. This reaction is exothermic. Use this information to explain why the temperature of the mine never falls below 17 oC even in cold winters. The air inside the mine contains 19% oxygen. Which one of the following best describes the oxygen level inside the mine compared with that outside the mine? Tick one box. the level of oxygen inside the mine is higher the level of oxygen is the same the level of oxygen is about a quarter of that of the outside air the level of oxygen inside the mine is lower
0620_w05_qp_2
THEORY
2005
Paper 2, Variant 0
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Use Copper can be extracted by heating copper carbonate with carbon. The copper carbonate breaks down into copper oxide and releases a gas. Complete the equation for this reaction. CuCO3 CuO + The copper oxide then reacts with the carbon. 2CuO + C 2Cu + CO2 heat Complete the following sentences using words from the list. endothermic exothermic halogen metal neutralised oxidised reduced In this reaction copper oxide is to copper. The copper obtained is a pinkish-brown The reaction is because heat is absorbed. State the name of the substance which is oxidised during this reaction. How would you test for the carbon dioxide given off in this reaction? test result Describe a test for aqueous copper ions and state the result. Examiner's Use Carbon is in Group IV of the Periodic Table. Draw a diagram to show how the electrons are arranged in an atom of carbon. To which Period in the Periodic Table does carbon belong? Organic compounds contain carbon and hydrogen. To which homologous series does the organic compound A belong? H H H C H H C H compound A State the name of compound A.
0620_w06_qp_2
THEORY
2006
Paper 2, Variant 0
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For Examiner's Use Calcium carbonate is an important raw material. Name a rock which is made up of calcium carbonate. When calcium carbonate is heated strongly, it decomposes. CaCO3 → CaO + CO2 Calculate the relative formula mass of: CaCO3 CaO 7.00 kg of calcium oxide was formed. What mass of calcium carbonate was heated? Calcium carbonate is used to control soil acidity. Why is it important to control soil acidity? Both calcium carbonate, insoluble in water, and calcium oxide, slightly soluble, are used to increase soil pH. Suggest two advantages of using calcium carbonate. Give one use of calcium carbonate other than for making calcium oxide and controlling soil pH.
0620_w06_qp_3
THEORY
2006
Paper 3, Variant 0
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For Examiner's Use The diagram shows the structures of calcium chloride, calcium and chlorine. Ca Ca Ca Ca Ca Ca Ca Ca Ca Ca Ca Ca2+ Cl – Cl – Ca2+ Cl – Cl – Ca2+ Cl – Cl – Ca2+ Cl – Cl – Cl Cl Cl Cl Cl Cl Cl Cl calcium chloride calcium chlorine Use ideas about structure and bonding to explain the following: Calcium chloride conducts electricity when molten but not when solid. At room temperature, calcium is a solid but chlorine is a gas. For Examiner's Use Calcium is manufactured by the electrolysis of molten calcium chloride. calcium – + molten calcium chloride water-cooled steel cathode State the products formed at the anode, at the cathode. Suggest a non-metal that can be used as an anode in this electrolysis. A stream of inert gas is blown over the calcium as it is removed from the molten calcium chloride. Suggest why a stream of inert gas is blown over the hot calcium. State the name of a gas which is inert. Aqueous sodium hydroxide or aqueous ammonia can be used to test for calcium ions in solution. Describe the results of these tests with aqueous sodium hydroxide, with aqueous ammonia.
0620_w08_qp_2
THEORY
2008
Paper 2, Variant 0
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