Flame Tests Flashcards
What are flame tests used for?
Indicate the presence of certain metal ions
How do you conduct a flame test?
Dip a clean wire loop into a sample of the compound being tested, then place the loop into the edge of a blue flame from a Bunsen burner
What colour do lithium ions turn the flame? (Li+)
Red
What colour do sodium ions turn the flame? (Na+)
Yellow
What colour do potassium ions turn the flame? (K+)
Lilac
What colour do calcium ions turn the flame? (Ca2+)
Orange-red
What colour do copper ions turn the flame? (Cu2+)
Blue-green
What is an ion?
Electrically charged particle, formed when an atom or molecule gains or loses electrons
What does adding dilute sodium hydroxide (NaOH) identify
certain positive ions in solution
What coloured precipitate do copper ions produce? (Cu2+)
Blue precipitate
What coloured precipitate do iron (|||) ions produce? (Fe3+)
Brown precipitate
What coloured precipitate do iron (||) ions produce? (Fe2+)
Green precipitate
Which ions produce a white precipitate?
Aluminium (Al3+), calcium (Ca2+), magnesium (Mg2+)
What happens when you add excess sodium hydroxide to aluminium hydroxide?
Redissolves
What happens when NaOH is warmed with ammonium ions (NH4+)
ammonia gas is produced, which is alkaline so it turns damp red litmus paper blue.
