Acids and Bases

• acids turn red litmus paper red
• acids turn blue litmus paper red
• alkalis turn red litmus paper blue
• alkalis turn blue litmus paper blue
• universal indicator

  tells how acidic or alkaline a solution is
• 0-2 strong acid
• 3-6 weak acid
• The pH of a neutral solution is 7.
• 8-11 weak alkali
• 12-14 strong alkali
• all acids contain hydrogen ions
• HCl -> H + Cl
• An acid is a substance that dissolves in water to give H+ ions
• strong acids produce a high concentration of H+ ions
• strong acids

  hydrochloric acid, nitric acid, sulfuric acid
• weak acids produce a low concentration of H+
• Only some acid molecules form ions
• weak acids

  carbonic acid, ethanoic acid
• a base is a metal oxide or hydroxide which neutralises an acid to produce a salt and water
• an alkali is a soluble base
• in water alkalis break up to form hydroxide ions OH-
• strong alkalis produce a high concentration of OH ions
• strong alkalis


  sodium hydroxide, potassium hydroxide
• weak alkalis produce a low concentration of hydroxide ions
• weak alkalis

  ammonia, limewater
• a solution can be dilute or concentrated
• ACID + BASE -> SALT + WATER
• neutralisation is exothermic
• Ionic equation for neutralisation

  H + OH -> H2O#
• neutralisation apparatus

  A) acid

  B) alkali

  C) burette

  D) stand

  E) conical flask

  F) white tile

  
• a salt is a compound formed when some/all of the hydrogen ions in an acid are replaced by metal ions or ammonium ions
• the pH scale measures how acidic or basic a substance is, with values ranging from 0 to 14.
• acid + base -> salt + water
• acidic solutions have a low pH value (less than 7)
• basic solutions have a high pH value (greater than 7)
• weak acids only partially ionise in solution
• neutral substances have a pH value of exactly 7
• metal + acid -> salt + hydrogen (mash)
• MASH observations

  MAGNESIUM- Heat, bubbles of gas, colourless solution, solid disappears, squeaky pop

  ZINC- bubbles of gas form, colourless solution, squeaky pop

  COPPER- No reaction
• Base + Acid -> Salt + Water (BASW)