acid and bases

• pH scale


  measure of the concentration of hydrogen ions in a solution. It is a continuous scale from below 0 to above 14.
• pH paper or universal indicator solution turns green in

  neutral solutions
• pH paper or universal indicator solution turns red or orange in

  acidic solution
• pH paper or universal indicator solution turns blue or purple in

  alkaline solution
• Acidic solutions have a pH that is

  below 7
• Alkaline solutions have a pH _____

  between 7 and 14
• hydrochloric acid formula

  HCl
• Sulfuric acid formula


  H2SO4
• Nitric acid formula


  HNO3
• Ethanoic acid formula


  CH3COOH
• sodium hydroxide formula


  NaOH
• calcium hydroxide formula


  Ca(OH)2
• lithium hydroxide formula


  LiOH
• What does the pH scale measure?

  the concentration of hydrogen ions in a solution
• When an acid is diluted with water, the concentration of H+ ions


  decreases; this increases the pH of the solution towards 7.
• When an alkali is diluted with water, the concentration of OH- ions


  decreases; this decreases the pH of the solution towards 7.
• When a soluble metal oxide dissolves in water an ____ _____ is formed.

  alkaline solution
• When a soluble non-metal oxide is dissolved in water an ___ ____ is formed.

  acidic solution
• A solution containing equal numbers of hydrogen ions and hydroxide ions is

  a neutral solution
• Neutralisation reaction


  acid + base = salt + water
• pH


  Chemical property of substances that allows us to divide them into two categories. It is a measure of the number of hydrogen ions that a substance contains- and therefore how acidic or alkaline it is- and runs on a scale of 1 to 14.

  
• Acid


  Substance with a pH of 6 or less, formed when a non-metal oxide reacts with water. It contains a higher proportion of hydrogen ions than hydroxide ions. Examples include vinegar, hydrochloric acid and nitric acid.
• Base


  Substance that can neutralise an acid. They come in three forms: metal hydroxide, metal oxide, and metal carbonate. Examples include calcium carbonate, sodium hydroxide and oven cleaner.
• Alkali


  Substance with a pH of 8 or more, formed when a metal oxide reacts with water. It contains a greater proportion of hydroxide ions than hydrogen ions. Examples include sodium hydroxide and potassium hydroxide.
• Neutral

  A _____ substance has a pH of 7, and has an equal balance of hydrogen and hydroxide ions. Examples include water and sodium chloride.
• Salt


  Product of a neutralisation reaction which is neutral. It is named after the parent acid and base, e.g, sodium chloride, potassium nitrate. Insoluble versions can also be created in precipitation reactions.
• Neutralisation


  Chemical reaction between an acid and base. Products always include water and a salt, but can also include carbon dioxide in the case of the base being a metal carbonate.

  
• Precipitation


  A reaction where a solid is formed. Two soluble salts can react with one another in such a reaction to produce an insoluble salt and a soluble salt, e.g, magnesium iodide + silver nitrate= magnesium nitrate (aq) + silver iodide (s).

  
• Titration


  Accurate method of measuring volumes of acids and alkalis necessary to neutralise one another. A practical experimentation technique, it uses a burette, pipette and conical flask, with known volumes of acid and alkali.

  
• Concordant


  Titration results are _______ if they are within 0.2 cm3 of one another.
• Titration calculation


  Calculation based on results of a titration, e.g, 20 cm3 of nitric acid was used to neutralise 20cm3 of 2 moll-1 sodium hydroxide. Assuming that one mole of the acid is equal to one mole of the alkali, what is the concentration of the nitric acid?
• Spectator ion


  An ion that does not undergo chemical change, but is present for the duration of a chemical reaction.

  
• Hydroxide ion


  Ion found in higher ratios compared to hydrogen ions in bases.

  
• Hydrogen ion


  Ion found in higher ratios compared to hydroxide ions in acids.

  
• Metal carbonate


  A type of base that produces water, carbon dioxide and a salt in a neutralisation reaction with an acid.
• Metal oxide


  Compound that produces an alkali when it reacts with water.
• Non-metal oxide


  Compound that produces an acid when it reacts with water.
• Indicator


  Substance used to tell us when neutralisation has taken place in a titration experiment.
• End-point


  The finishing point of a chemical reaction.
• Precipitate

  General term used for a solid substance created in a precipitation reaction.