Question
CaCO3(s) → CaO(s) + CO2(g)
Name three statements?
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Question
Which substance is removed by the lime?
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IGCSE CHEMISTRY
CHAPTER 13
Question | Answer |
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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); |