Chemistry Form 3

Contenido

1. 1. Chemical Equations

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   Teoría

   • Writing chemical equations
   • Balancing chemical equations
   • Ionic equations
   • Types of chemical reactions
   • Information from a balanced equation
   • Summary

   What is a chemical equation? A chemical equation is a short way of describing a chemical reaction using symbols and formulae. The starting substances are the reactants (on the left) and the new substances are the products (on the right), separated by an arrow. Word equation: magnesium + oxygen → magnesium oxide Symbol…

2. 2. Hardness of Water

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   Teoría

   • Soft and hard water and how water becomes hard
   • Soap, scum and the two types of hardness
   • Methods of removing hardness
   • Advantages and disadvantages of hard water
   • Summary

   Soft and hard water Soft water forms lather easily with soap. Hard water does not form lather easily with soap; instead it forms a grey solid called scum . Hardness is caused by dissolved calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ) . Soap is sodium stearate (C 17 H 35 COONa). The calcium ions react with it to…

3. 3. Acids, Bases and Salts

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   Teoría

   • Acids and their properties
   • Bases and alkalis
   • Indicators, pH and neutralization
   • Salts and their solubility
   • Preparation of salts
   • Summary

   Acids An acid is a substance that produces hydrogen ions (H + ) as the only positive ions when dissolved in water. Mineral acids: hydrochloric (HCl), sulphuric (H 2 SO 4 ), nitric (HNO 3 ). Organic acids: ethanoic acid (vinegar), citric acid (lemons), lactic acid (sour milk). A strong acid ionizes completely in water…

4. 4. The Mole Concept and Related Calculations

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   Teoría

   • The mole, relative masses and molar mass
   • Calculations with moles, masses, particles and gas volumes
   • Percentage composition, empirical and molecular formulae
   • Reacting masses and volumes from equations
   • The gas laws
   • Summary

   The mole Atoms are too small to count one by one, so chemists count them in large groups called moles . One mole is the amount of substance containing 6.02 × 10 23 particles (atoms, molecules or ions). This number is the Avogadro constant (L). Molar mass The molar mass is the mass of one mole of a substance in grams;…

5. 5. Quantitative and Volumetric Analysis

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   Teoría

   • Concentration of solutions
   • Standard solutions and dilution
   • Titration: apparatus, procedure and indicators
   • Acid–base titration calculations
   • Further volumetric calculations
   • Summary

   What is volumetric analysis? Quantitative analysis finds how much of a substance is present. Volumetric analysis does this by measuring volumes of solutions that react completely with each other, usually by titration . Concentration Molarity (mol/dm 3 , M) = moles of solute ÷ volume of solution in dm 3 . Mass…

6. 6. Ionic Theory and Electrolysis

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   Teoría

   • Conductors, electrolytes and non-electrolytes
   • Electrolysis of molten compounds
   • Electrolysis of aqueous solutions and selective discharge
   • Faraday's laws of electrolysis
   • Applications of electrolysis
   • Summary

   Electrolytes and non-electrolytes An electrolyte is a compound that conducts electricity when molten or dissolved in water and is decomposed by it. It contains ions that are free to move. Strong electrolytes are fully ionized (NaCl solution, dilute H 2 SO 4 , NaOH); weak electrolytes are partly ionized (ethanoic acid,…

7. 7. Chemical Kinetics, Equilibrium and Energetics

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   Teoría

   • Rate of reaction and how it is measured
   • Collision theory and factors affecting the rate
   • Reversible reactions and chemical equilibrium
   • Energy changes in chemical reactions
   • Measuring heats of reaction
   • Summary

   Rate of reaction Chemical kinetics is the study of the rates of reactions. The rate of reaction is the change in amount (or concentration) of a reactant or product per unit time. It can be followed by measuring the volume of gas given off, the loss in mass, or the time for a colour or precipitate to appear. Example: if…

8. 8. Extraction of Metals

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   Teoría

   • Occurrence of metals and the choice of extraction method
   • Stages in the extraction of metals
   • Extraction of iron: the blast furnace
   • Extraction of sodium and aluminium by electrolysis
   • Extraction of copper and zinc, and environmental effects
   • Summary

   Occurrence of metals Very unreactive metals such as gold and platinum occur free ( native ). Most metals occur combined in ores – rocks from which a metal can be extracted profitably. Examples: haematite Fe 2 O 3 and magnetite Fe 3 O 4 (iron), bauxite Al 2 O 3 ·2H 2 O (aluminium), copper pyrites CuFeS 2 , zinc blende…

9. 9. Compounds of Metals

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   Teoría

   • Effect of heat on carbonates, hydrogencarbonates and hydroxides
   • Effect of heat on nitrates and sulphates
   • Sodium chloride and sodium hydroxide
   • Calcium oxide, calcium hydroxide and calcium carbonate
   • Sodium carbonate, sulphates and the behaviour of salts in air
   • Summary

   Introduction Metals form many useful compounds: oxides, hydroxides, carbonates, hydrogencarbonates, nitrates, chlorides and sulphates. The stability of these compounds to heat depends on the reactivity of the metal: compounds of very reactive metals (K, Na) are the most stable. Effect of heat on compounds Compound K,…