Acids, bases and salts

• What is the pH scale?

  A measure of proportion of hydrogen ions in a substance
• 0-6 on the pH scale means that the substance is acidic
• If the number on the pH scale is 7, then the substance is neutral
• 8-14 on the pH scale means that the substance is an alkaline
• Water is neutral
• What does H2O split into?

  H+ (acid) and OH - (alkali) which cancels out
• What is the symbol for sulphuric acid?

  H2SO4
• What is the symbol for nitric acid?


  HNO3
• What is the symbol for hydrochloric acid?

  HCl
• When a metal reacts with an acid it gives off hydrogen and the other product is a salt
• What is included in a MASH reaction?

  Metal + acid -> salt + hydrogen
• What are indicators?


  Substances that change colour when they are added to acidic or alkaline solutions
• What is the most commonly used indicator?

  Universal indicator
• What is universal indicator?

  A mixture of indicators which can be used to measure the pH of a solution
• What colour are strong acids in the presence of indicator?


  Red and orange
• What colour are weak acids in the presence of indicator?


  Yellow and green
• What colour will neutral substances turn in the presence of indicator?

  Green
• What colour will weak alkalines turn in the presence of indicator?


  Blue
• What colour will strong alkalines turn in the presence of indicator?

  Blue and purple
• When acids dissolve in water they produce H+ ions
• (aq) stands for aqueous
• Acids are often produced from non metal oxides
• When alkalis dissolve in water, they produce OH- ions
• What is a base?

  Chemically opposite to an acid. Some bases are alkalis as they dissolve in water
• What happens in a neutralisation reaction?

  When water is produced. H(+) + OH(-) -> H2O
• A neutralisation reaction involves the loss and gain of hydrogen ions
• When carbon dioxide is released in a reaction, it means the reaction is fizzing
• pH values of strong acids are lower than weak acids because weak acids don't fully dissolve in water. This also explains why there is a temperature rise during a reaction with strong acids is higher.
• A dilute acid has acid molecules mixed with a large volume of water. Meaning that there are only a low concentration of H+ molecules
• Concentrated acids have little to no water molecules mixed with acid molecules. Meaning that the concentration of H+ ions is high
• To identify an acid, you would react it with a metal carbonate. You would see fizzing which gives off CO2
• CO2 turns limewater milky
• To identify a carbonate, you would react it with an acid. You would see fizzing which gives off CO2
• To identify a sulfate, you would react it with barium chloride. You would see white ppt.
• What is the equation for identifying a sulfate using barium chloride?

  Ba(2+) + SO4(-2) -> BaSO4
• What type of reaction is it where a metal is reacted with an acid?

  Exothermic
• When acids are reacted with metal hydroxides, a salt and water is created
• Where does the first part of a salt's name come from?


  Metal (oxide or carbonate)
• Where does the second part of a salt's name come from?

  The acid
• Ammonia forms ammonium salts when it is reacted with an acid