metal hydroxides

• sodium hydroxide solutions can be used to identify some metal ions (cations)
• test for ALUMINIUM/CALCIUM/MAGNESIUM

  add sodium hydroxide

  • white precipitate

  if excess added, the aluminium precipitate dissolves

  calcium = flame test = orange/red flame
• test for calcium equation:

  calcium nitrate + sodium hydroxide --> sodium nitrate + calcium hydroxide

  Ca(NO3) + 2NaOH --> 2NaNO3 + Ca(OH)2
• test for magnesium equation:

  magnesium nitrate + sodium hydroxide --> sodium nitrate + magnesium hydroxide

  Mg(NO3)2 + 2NAOH --> 2NaNO3 + Mg(OH)2
• test for aluminium equations;

  aluminium nitrate + sodium hydroxide --> sodium nitrate + aluminium hydroxide

  Al(NO3)3 + 3NaOH --> 3NaNO3 + Al(OH)3
• copper(II) react with sodium hydroxide to form a BLUE precipitate

  equation: copper nitrate + sodium hydroxide --> sodium nitrate + copper hydroxide
• iron(II) reacts with sodium hydroxide to form a GREEN precipitate
• iron(III) react with sodium hydroxide to form a BROWN precipitate