CALCIUM CARBONATE A guide for GCSE students KNOCKHARDY

CALCIUM CARBONATE A guide for GCSE students KNOCKHARDY PUBLISHING 2010 SPECIFICATIONS

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 A 2 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 Ca. CO 3 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 CO 3 unit The compounds are ionic; the formula is found by balancing the charges of the ions Carbonate ions have a 2 - charge CO 32 CALCIUM CARBONATE Ca. CO 3 SODIUM CARBONATE Na 2 CO 3

CARBONATES Formulae All carbonates contain the CO 3 unit Chemical formula sodium carbonate Na 2 CO 3 calcium carbonate Ca. CO 3 magnesium carbonate Mg. CO 3 copper carbonate Cu. CO 3

PROCESSING LIMESTONE Roasting Heating limestone very strongly makes it break up The process is known as THERMAL DECOMPOSITION calcium carbonate Ca. CO 3 —> —> calcium oxide + Ca. O carbon dioxide + Calcium oxide is also known as QUICKLIME CO 2

ACTION OF HEAT ON METAL CARBONATES METHOD Place a small amount of one of the solid carbonates in a dry test tube. Place about 2 cm 3 of lime water in another test tube. Heat the solid, gently at first, then more strongly. CO 2 lime water metal carbonate Test any gas with the limewater. Appearance Calcium carbonate Ca. CO 3 Copper carbonate Cu. CO 3 Magnesium carbonate Mg. CO 3 Zinc carbonate Zn. CO 3 CO 2 produced Residue Conclusion

ACTION OF HEAT ON METAL CARBONATES Appearance Calcium carbonate Ca. CO 3 Copper carbonate Cu. CO 3 Magnesium carbonate Mg. CO 3 Zinc carbonate Zn. CO 3 CO 2 produced Residue Conclusion WHITE SOLID Calcium oxide formed (needs very GREEN SOLID BLACK SOLID Copper oxide formed WHITE SOLID Magnesium oxide formed YELLOW SOLID WHICH TURNS WHITE WHEN COOL Zinc oxide formed WHITE SOLID strong heating) Sodium carbonate (Na 2 CO 3) also decomposes on heating but it requires more heat than an ordinary bunsen burner can supply.

THERMAL DECOMPOSITION OF CARBONATES All metal carbonates decompose when heated to form carbon dioxide and a metal oxide. The process is known as THERMAL DECOMPOSITION calcium carbonate —> calcium oxide + copper carbonate —> copper oxide magnesium carbonate —> magnesium oxide sodium carbonate * —> sodium oxide + zinc carbonate —> zinc oxide carbon dioxide + + carbon dioxide * 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 carbonates decompose when heated to form carbon dioxide and a metal oxide. The process is known as THERMAL DECOMPOSITION calcium carbonate —> calcium oxide copper carbonate —> copper oxide magnesium carbonate —> magnesium oxide sodium carbonate * —> sodium oxide + zinc carbonate —> zinc oxide carbon dioxide + + + carbon dioxide * 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 + Ca. CO 3 —> Ca. O + CO 2 + Cu. CO 3 —> Cu. O + CO 2 + Mg. CO 3 —> Mg. O + CO 2 + Na 2 CO 3 —> Na 2 O + CO 2 + Zn. CO 3 —> Zn. O + CO 2

THERMAL DECOMPOSITION OF CARBONATES + Ca. CO 3 —> Ca. O + CO 2 + Cu. CO 3 —> Cu. O + CO 2 + Mg. CO 3 —> Mg. O + CO 2 + Na 2 CO 3 —> Na 2 O + CO 2 + Zn. CO 3 —> Zn. O + CO 2

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

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 CO 2 is present) calcium hydroxide + carbon dioxide ——> calcium carbonate + water Ca(OH)2 + CO 2 ——> Ca. CO 3 + H 2 O

LIMESTONE CYCLE HE AT CALCIUM CARBONATE (limestone) AQUEOUS CALCIUM HYDROXIDE (lime water) CALCIUM OXIDE (quicklime) HE AT 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 paths filling cracks, holes cement (1) large chippings (4½) small chippings (3½) 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 carbonates react 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 Good - acid rain attacks limestone rocks in the countryside - monuments and statues are attacked - carbonates can neutralise excess acid in the stomach

REACTION OF ACIDS WITH CARBONATES All carbonates react 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 carbonates react 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 NITRIC ACID SULPHURIC ACID produces CHLORIDES NITRATES SULPHATES

REACTION OF ACIDS WITH CARBONATES All carbonates react 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 + carbonate hydrochloric acid —> calcium chloride + carbon + dioxide water sodium + carbonate sulphuric acid —> sodium sulphate + carbon dioxide + water copper + carbonate nitric acid —> copper nitrate + carbon + dioxide water HYDROCHLORIC ACID NITRIC ACID SULPHURIC ACID produces CHLORIDES NITRATES SULPHATES

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

AQA C 1. 2. 1 Calcium carbonate - summary a) Limestone, mainly composed of the compound calcium carbonate (Ca. CO 3), 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 aggregate to make concrete.