flame test + testing for ions Flashcards
what group 1 elements are tested in the flame test
- lithium
- potassium
- sodium
what flame colour does lithium ion produce
red
what flame colour does potassium ion produce
lilac
what flame colour does sodium ion produce
yellow
what group 2 elements are tested in the flame test
- magnesium
- calcium
- strontium
- barium
what flame colour does magnesium ion produce
no colour
what flame colour does calcium ion produce
yellow-red
what flame colour does strontium ion produce
crimson red
what flame colour does barium ion produce
pale green
describe in terms of electrons an explanation for the colours produced in these tests
- energy supplied to electrons they are temporarily promoted to orbitals with a higher energy level
- electrons drop back down to their original orbital, releasing energy, some of this energy in the form of light energy
- a colour is produced depending on the wavelength of the light energy emitted
why do some ions not produce a colour in the flame test
when electrons return to their original orbital, the light energy emitted may not have a wavelength in the visible light part of the electromagnetic spectrum
what anions do we test for
- sulfate (SO4^2-)
- Carbonate (CO3^2-) + Hydrocarbonate (HCO3^-)
describe test for sulfate ions + general equation
- use acidified BaCl2, will form a white precipitate BaSO4
(BaCl2 + XSO4 –> BaSO4 + XCL2)
describe test for carbonate and hydrocarbonate ions + general equation
- add HCl, substance containing CO3^2- ions will fizz, CO2 gas is given off
- bubble gas through limewater, if CO2 is present it will turn cloudy in a positive result
(XCO3 + HCl –> CO2 + H2O + XCl2)
what cations do we test for
- ammonium (NH4+)
