bases/alkalis

• a base is a proton accepter
• it accepts protons from the acid
• when an acid reacts with a base a neutralisation reaction occurs whereby a salt and water is produced
• base + acid = salt + water
• most metal oxides - Magnesium oxide (MgO) and metal hydroxides - Copper hydroxide, Cu(OH)2
• an alkali is a substance which produces hydroxide ions OH- when dissolved in water
• an alkali is a soluble base, a base that dissolves in water is alkali
• they are good electrical conductors
• alkalis and bases turn red litmus paper blue
• pH greater than 7
• they have a bitter taste
• they have a soapy feel
• strong alkalis are corrosive
• sodium hydroxide or caustic soda- NaOH

  source- lye (drain cleaner), paint stripper
• calcium hydroxide- Ca(OH)2

  source- lime water, slaked lime
• magnesium hydroxide- Mg(OH)2

  source- toothpaste, milk of magnesia
• potassium hydroxide- KOH

  source- paint remover, fabric dye
• ammonia solution- NH3(aq)

  or ammonia hydroxide- NH4OH

  source- household cleaners, manufacture of fertilizers
• calcium oxide- CaO

  source- reduces soil acidity by neutralising it
• calcium hydroxide- Ca(OH)2

  source- reduces soil acidity
• base + ammonium salt = salt + water + ammonia

  calcium hydroxide + ammonium chloride = calcium chloride + water + ammonia
• strong acids are completely ionised or disssociated with hydroxide ions when dissovled in water
• weak alkalis are partially ionised or dissociated into hydroxide ions when dissolved in water
• the higher the pH the stronger the alkali
• the lower the pH the weaker the alkali
• wasps stings are alkaline-

  use a weak acid like vinegar to neutralise the sting