TYPES OF CHEMICAL REACTIONS

• Acids


  When added to water, they form positively charged hydrogen ions (H+)
• Alkalis


  When added to water, they form negative hydroxide ions (OH-)
• pH scale


  • Numerical scale which is used to show how acidic or alkaline a solution is
  • Measures the amount of ions present in solution
  • Goes from 1 - 14
  • Acids have pH values below 7
  • Alkalis have pH values above 7
  • pH 7 is neutral
• Measuring pH


  1. Using an indicator

  2. Using a digital pH meter
• Indicator


  Substance which changes colour depending on the pH of the solution
• Types of indicators


  • Natural indicators
  • Synthetic indicators
• Synthetic indicators


  • Have very narrow pH ranges
  • Have sharp colour changes
• Natural indicators


  • Wide range indicators
  • Contain a mixture of different plant extracts
  • Can operate over a broad range of pH values
• Neutralisation reaction


  Acid + base -> salt + water
• Acids react with metal oxides and hydroxides


  Produces a salt and water
• Acids that produce specific salts

  • Hydrochloric acid produces chlorides
  • Sulfuric acid produces sulfate salts
  • Nitric acid produces nitrates
• Acids react with metal carbonates

  Produces a salt, carbon dioxide and water
• Acids that produce specific salts with metal carbonates

  • Hydrochloric acid produces metal chlorides
  • Sulfuric acid produces metal sulfates
  • Nitric acid produces metal nitrates
• Acids and metals


  • Only metals above hydrogen in the reactivity series will react with dilute acids
  • More reactive metals react more vigorously
• Reaction of acids with metals


  Metal + acid -> salt + hydrogen
• Examples of acid-metal reactions


  • Magnesium + sulfuric acid -> magnesium sulfate + hydrogen
  • Zinc + hydrochloric acid -> zinc chloride + hydrogen
  • Iron + sulfuric acid -> iron sulfate + hydrogen
• Naming salts


  • First part comes from the metal, metal oxide, metal hydroxide or metal carbonate
  • Second part comes from the acid
• Not all reactions of acids are neutralisations
• Strong acids


  Dissociate completely in water, producing solutions with a high concentration of H+ ions and thus a very low pH
• Weak acids


  Only partially ionise in water, producing solutions of pH values between 4 - 6
• Concentrated vs dilute acids

  • Concentration refers to how many acid particles there are in a certain volume
  • A concentrated solution will have more acid particles than a dilute one per dm3
• Strong vs weak acids

  Strong and weak refer to the ability of an acid to dissociate
• A dilute solution of a strong acid can have a lower pH than a concentrated solution of a weak acid
• pH


  • Measure of the concentration of H+ ions in solution
  • Logarithmic scale, each change of 1 represents a change in concentration by a factor of 10
• Titration curves


  1. Show the effect of changing hydrogen ion concentration on pH

  2. When a base is added to an acid, pH increases rapidly

  3. When an acid is added to a base, pH decreases rapidly
• Substances are made of atoms
• Element


  Different types of atoms represented in the periodic table by a symbol
• Compound


  Substance that contains two or more different types of atoms chemically bonded together
• Chemical reaction


  Atoms change what they're bonded to and how they're bonded
• Word equation


  Representation of a chemical reaction using words
• Chemical equation


  Representation of a chemical reaction using symbols
• Atoms are not created or destroyed in a chemical reaction, the same number of each type of atom must be on both sides of the equation</b>
• Balancing a chemical equation

  Start with atoms only in compounds, then balance elements
• Mixture


  Any combination of different types of elements and compounds that are chemically bonded together
• Mixtures


  • Air
  • Salt water
• Separating mixtures


  1. Filtration

  2. Crystallization

  3. Distillation
• Physical processes like filtration, crystallization, and distillation do not create new substances, they are not chemical reactions
• Purity


  Determined by testing the melting point or boiling point, a pure substance has a very specific temperature
• Formulation


  A mixture that has been specially designed to be useful in a very specific way
• Formulations


  • Paints
  • Fuels
  • Alloys
  • Fertilizers