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IGCSE CHEMISTRY

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Created by: Haridus Academy

Question	Answer
When limestone is heated it forms lime (calcium oxide) and carbon dioxide. CaCO3(s) → CaO(s) + CO2(g) Name three statements?	1 Carbon dioxide is a greenhouse gas which may contribute to climate change. 2 Slaked lime is used to neutralise industrial waste. 3 This reaction is an example of thermal decomposition
Lime (calcium oxide) is used to treat waste water from a factory. Which substance is removed by the lime?	Sulfuric acid
Which process is used to make lime (calcium oxide) from limestone (calcium carbonate)?	Thermal decomposition
Why is lime added to the soil before planting the vegetable?	The lime is an indicator
In which process is carbon dioxide not formed?	Heating lime
Which process does not produce carbon dioxide?	The treatment of acidic soil with lime
Carbon dioxide is produced when dilute hydrochloric acid reacts with.........	Copper(II) carbonate
Quicklime, which is calcium oxide, is made by heating limestone in a furnace. CaCO3(s) CaO(s) + CO2(g) The reaction does not come to equilibrium. Suggest why the conversion to calcium oxide is complete.	Carbon dioxide escapes
Calcium hydroxide, slaked lime, is made from calcium oxide. Write an equation for this reaction	CaO + H2O € Ca(OH)2
Explain in 3 points the chemistry of desulfurization of flue gases.	Flue gas contains sulfur dioxide; Sulfur dioxide is acidic; Calcium carbonate reacts with sulfur dioxide;
Give one other use of calcium carbonate	Making of steel or iron
Explain in two terms of collisions between reacting particles each of the following. The reaction rate would be slower if 20.0 g of larger lumps of calcium carbonate and 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3, were used	Smaller surface area Lower collision rate
Explain in three terms of collisions between reacting particles each of the following. The reaction rate would be faster if the experiment was carried out at a higher temperature	Molecules have more energy Collide more frequently More molecules have enough energy to react
Lead has a metallic structure which is a lattice of lead ions surrounded by a ‘sea’ of mobile electrons. This structure is held together by attractive forces called a metallic bond. Explain why there are attractive forces in a metallic structure.	Attractive force between positive ions and negative electrons
Explain why a metal, such as lead, is malleable.	Layers of lead ions
Soda lime is a mixture of sodium hydroxide and calcium oxide. Why do these two substances react with carbon dioxide?	Carbon dioxide is acidic Sodium hydroxide and calcium oxide are bases
Name two substances formed when soda lime reacts with carbon dioxide	Calcium carbonate Sodium carbonate
Calcium carbonate is an important raw material. Name six rocks which is made up of calcium carbonate	Limestone Marble Chalk Coral Calcite Aragonite
When calcium carbonate is heated strongly, it decomposes. CaCO3 → CaO + CO2 Calculate the relative formula mass of: CaCO3	100
7.00 kg of calcium oxide was formed. What mass of calcium carbonate was heated?	7.00kg is 1/8 of 56 1/8 of 100kg is 12.5kg
Calcium carbonate is used to control soil acidity. Why is it important to control soil acidity? Name 3 points.	Plants prefer soil pH about 7 Plants do not grow (well) in acidic soils Plants grow better To increase crop yields
Both calcium carbonate, insoluble in water, and calcium oxide, slightly soluble, are used to increase soil pH. Suggest three advantages of using calcium carbonate.	With calcium carbonate, pH cannot go above 7 It is not washed away by the rain Remains longer in the soil It is not absorbed by the plant
Give two uses of calcium carbonate other than for making calcium oxide and controlling soil pH.	Making steel Making iron
Name three waste gases that leave the blast furnace	Carbon dioxide; Carbon monoxide; Nitrogen;
Describe how the malleability of iron changes as the percentage of carbon changes.	As the percentage of carbon increases, so the malleability decreases;
Iron obtained from the blast furnace contains high levels of carbon. Explain how the amount of carbon in the iron can be decreased	Oxygen (gas) blown in; Carbon dioxide formed C + O2 → CO2
Iron from the Blast Furnace is impure. It contains 5% of impurities, mainly carbon, sulfur, silicon and phosphorus, which been removed when iron is converted to steel. Explain in 5 how the addition of oxygen and calcium oxide removes these impurities.	Forming an oxide in elements Gaseous oxides in carbon dioxide Acidic oxides in Silcon Equation mark - S + O2 € SO2; Word equation mark - calcium oxide + phosphorus(III / V) oxide € calcium phosphate;
Mild steel is the most common form of steel. Mild steel contains a maximum of 0.3% of carbon. High carbon steel contains 2% of carbon. It is less malleable and much harder than mild steel. Give three uses of mild steel	Machinery; Chains; Pylons;
Suggest a use of high carbon steel	Knives; Drills; Railway tracks;
Explain why metals are malleable	Rows or layers slide over one another
Suggest an explanation why high carbon steel is less malleable and harder than mild steel.	Carbon atoms or particles in structure different size (to cations);