CALCIUM CARBONATE A guide for GCSE students

CALCIUM CARBONATE A guide for GCSE students 2010 SPECIFICATIONS KNOCKHARDY PUBLISHING

CALCIUM CARBONATE INTRODUCTION This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY SCIENCE WEBSITE at... www.knockhardy.org.uk/gcse.htm All diagrams and animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any commercial work.

LIMESTONE Limestone is made of calcium carbonate CaCO3 Origin Formed in the sea millions of years ago from the remains of shells Found in places like the Peak District of Derbyshire Extraction Quarried in large amounts e.g. 150 million tonnes each year in the UK IT IS AN IMPORTANT RAW MATERIAL Use building material and road chippings neutralising excess acid in lakes and soil making cement and concrete added to bread added to toothpaste

LIMESTONE PRODUCTS ARE VERY USEFUL … especially in building houses CEMENT / MORTAR GLASS CONCRETE

CARBONATES Formulae All carbonates contain the CO3 unit The compounds are ionic; the formula is found by balancing the charges of the ions Carbonate ions have a 2- charge CO32- CALCIUM CARBONATE CaCO3 SODIUM CARBONATE Na2CO3

CARBONATES Formulae All carbonates contain the CO3 unit Chemical formula sodium carbonate Na2CO3 calcium carbonate CaCO3 magnesium carbonate MgCO3 copper carbonate CuCO3

PROCESSING LIMESTONE Roasting Heating limestone very strongly makes it break up The process is known as THERMAL DECOMPOSITION calcium carbonate —> calcium oxide + carbon dioxide CaCO3 —> CaO + CO2 Calcium oxide is also known as QUICKLIME

ACTION OF HEAT ON METAL CARBONATES CO2 METHOD Place a small amount of one of the solid carbonates in a dry test tube. Place about 2cm3 of lime water in another test tube. Heat the solid, gently at first, then more strongly. Test any gas with the limewater. lime water metal carbonate Appearance CO2 produced Residue Conclusion Calcium carbonate CaCO3 Copper carbonate CuCO3 Magnesium carbonate MgCO3 Zinc carbonate ZnCO3

ACTION OF HEAT ON METAL CARBONATES Appearance CO2 produced Residue Conclusion Calcium carbonate CaCO3 WHITE SOLID WHITE SOLID Calcium oxide formed (needs very strong heating)  Copper carbonate CuCO3 BLACK SOLID Copper oxide formed GREEN SOLID  Magnesium carbonate MgCO3 WHITE SOLID Magnesium oxide formed WHITE SOLID  Zinc carbonate ZnCO3 YELLOW SOLID WHICH TURNS WHITE WHEN COOL Zinc oxide formed WHITE SOLID  Sodium carbonate (Na2CO3) also decomposes on heating but it requires more heat than an ordinary bunsen burner can supply.

THERMAL DECOMPOSITION OF CARBONATES All metal carbonatesdecompose when heated to form carbon dioxide and a metal oxide. The process is known as THERMAL DECOMPOSITION calcium carbonate —> calcium oxide + carbon dioxide copper carbonate —> copper oxide + carbon dioxide magnesium carbonate —> magnesium oxide + carbon dioxide sodium carbonate * —> sodium oxide + carbon dioxide zinc carbonate —> zinc oxide + carbon dioxide *THE THERMAL DECOMPOSITION OF GROUP I METAL CARBONATES (SUCH AS SODIUM CARBONATE) REQUIRES A TREMENDOUS AMOUNT OF ENERGY – A BUNSEN BURNER IS NOT HOT ENOUGH +

THERMAL DECOMPOSITION OF CARBONATES All metal carbonatesdecompose when heated to form carbon dioxide and a metal oxide. The process is known as THERMAL DECOMPOSITION calcium carbonate —> calcium oxide + carbon dioxide copper carbonate —> copper oxide + carbon dioxide magnesium carbonate —> magnesium oxide + carbon dioxide sodium carbonate * —> sodium oxide + carbon dioxide zinc carbonate —> zinc oxide + carbon dioxide *THE THERMAL DECOMPOSITION OF GROUP I METAL CARBONATES (SUCH AS SODIUM CARBONATE) REQUIRES A TREMENDOUS AMOUNT OF ENERGY – A BUNSEN BURNER IS NOT HOT ENOUGH

THERMAL DECOMPOSITION OF CARBONATES Write out the chemical equations + CaCO3 —>CaO + CO2 CuCO3 —>CuO + CO2 MgCO3 —> MgO + CO2 Na2CO3 —> Na2O + CO2 ZnCO3 —> ZnO + CO2 + + + +

THERMAL DECOMPOSITION OF CARBONATES + CaCO3 —>CaO + CO2 CuCO3 —>CuO + CO2 MgCO3 —> MgO + CO2 Na2CO3 —> Na2O + CO2 ZnCO3 —> ZnO + CO2 + + + +

QUICKLIME Calcium oxide CaO Reacts with water to form SLAKED LIME (CALCIUM HYDROXIDE) calcium oxide + water ——> calcium hydroxide + HEAT CaO + H2O ——> Ca(OH)2 Use added to soil to make it less acidic added to lakes which have been polluted by acid rain

SLAKED LIME & LIME WATER Lime water is a solution of calcium hydroxide in water it is an alkali it is used to test for the gas carbon dioxide (limewater goes ‘cloudy’ if CO2 is present) calcium hydroxide + carbon dioxide ——> calcium carbonate + water Ca(OH)2 + CO2——> CaCO3 + H2O

HEAT HEAT LIMESTONE CYCLE CALCIUM CARBONATE (limestone) AQUEOUS CALCIUM HYDROXIDE (lime water) CALCIUM OXIDE (quicklime) SOLID CALCIUM HYDROXIDE (slaked lime)

CEMENT, CONCRETE & GLASS All three rely on limestone for their manufacture CEMENT powdered clay powdered limestone mix and roast them in a rotary kiln

CEMENT, CONCRETE & GLASS All three rely on limestone for their manufacture MORTAR cement sand water mortar is a ‘thin’ form of concrete used for bricklaying

CEMENT, CONCRETE & GLASS All three rely on limestone for their manufacture CONCRETE cement - bonds aggregate together sand powdered rock or chippings water - makes it easier to work with - causes a chemical reaction to harden the cement allow the mixture to dry slowly (set) you get a very hard solid it is much stronger than simple cement

CEMENT, CONCRETE & GLASS All three rely on limestone for their manufacture CONCRETE cement - bonds aggregate together sand powdered rock or chippings water - makes it easier to work with - causes a chemical reaction to harden the cement You choose the correct mixture for the job you are doing foundations, driveways cement (1) large chippings (4½) paths cement (1) small chippings (3½) filling cracks, holes cement (1) coarse sand (3) you must not add too much water otherwise it takes ages to dry don’t let it set too quickly otherwise it cracks avoid laying concrete when it is frosty - it disintegrates For plastering walls GYPSUM is used; it is a form of calcium sulphate

CEMENT, CONCRETE & GLASS All three rely on limestone for their manufacture GLASS made by heating a mixture of… limestone - calcium carbonate sand - silica soda - sodium carbonate + small amounts of other chemicals can be added to make special glass

REACTION OF ACIDS WITH CARBONATES All carbonatesreact with acids to form a salt, carbon dioxide and water. It is an example of a NEUTRALISATION REACTION CARBONATE + ACID —> A SALT + CARBON DIOXIDE + WATER Everyday examples Bad - acid rain attacks limestone rocks in the countryside - monuments and statues are attacked Good - carbonates can neutralise excess acid in the stomach

REACTION OF ACIDS WITH CARBONATES All carbonatesreact with acids to form a salt, carbon dioxide and water. It is an example of a NEUTRALISATION REACTION CARBONATE + ACID —> A SALT + CARBON DIOXIDE + WATER THE SALT THAT IS FORMED DEPENDS ON… THE METAL CARBONATE AND THE ACID USED

REACTION OF ACIDS WITH CARBONATES All carbonatesreact with acids to form a salt, carbon dioxide and water. It is an example of a NEUTRALISATION REACTION CARBONATE + ACID —> A SALT + CARBON DIOXIDE + WATER THE SALT THAT IS FORMED DEPENDS ON… THE METAL CARBONATE AND THE ACID USED HYDROCHLORIC ACID produces CHLORIDES NITRIC ACID produces NITRATES SULPHURIC ACID produces SULPHATES

REACTION OF ACIDS WITH CARBONATES All carbonatesreact with acids to form a salt, carbon dioxide and water. It is an example of a NEUTRALISATION REACTION CARBONATE + ACID —> A SALT + CARBON DIOXIDE + WATER calcium + hydrochloric —> calcium + carbon + water carbonate acid chloride dioxide sodium + sulphuric —> sodium + carbon + water carbonate acid sulphate dioxide copper + nitric —> copper + carbon + water carbonate acid nitrate dioxide HYDROCHLORIC ACID produces CHLORIDES NITRIC ACID produces NITRATES SULPHURIC ACID produces SULPHATES

REACTION OF ACIDS WITH CARBONATES magnesium + nitric —> magnesium + carbon + water carbonate acid nitrate dioxide zinc + hydrochloric —> zinc + carbon + water carbonate acid chloride dioxide sodium + nitric —> sodium + carbon + water carbonate acid nitrate dioxide zinc + sulphuric —> zinc + carbon + water carbonate acid sulphate dioxide copper + sulphuric —> copper + carbon + water carbonate acid sulphate dioxide potassium + hydrochloric —> potassium + carbon + water carbonate acid chloride dioxide

AQA C1.2.1 Calcium carbonate - summary • Limestone, mainly composed of the compound calcium carbonate (CaCO3), is quarried and can be used as a building material. • b) Calcium carbonate can be decomposed by heating (thermal decomposition) to make calcium oxide and carbon dioxide. • c) The carbonates of magnesium, copper, zinc, calcium and sodium decompose on • heating in a similar way to give carbon dioxide and the metal oxide. • Not all carbonates of metals in Group 1 of the periodic table decompose at the temperatures reached by a Bunsen burner. • d) Calcium oxide reacts with water to produce calcium hydroxide, which is an alkali that can be used in the neutralisation of acids. • e) A solution of calcium hydroxide in water (limewater) reacts with carbon dioxide to produce calcium carbonate. Limewater is used as a test for carbon dioxide. Carbon dioxide turns limewater cloudy. • f) Carbonates (eg Mg, Cu, Zn, Ca, Na) react with acids to produce carbon dioxide, a salt and water. Limestone is damaged by acid rain. • g) Limestone is heated with clay to make cement. Cement is mixed with sand to • make mortar and with sand and aggregate to make concrete.

CALCIUM CARBONATE A guide for GCSE students