Brainlag PlusFlame tests, metal hydroxide precipitates, and the tests for carbonate, halide and sulfate ions, put together to name an unknown salt.
Positive ions: flames and precipitates
Flame test: clean a nichrome loop in hydrochloric acid and heat it until it gives no colour, dip it in the solid and hold it in a blue Bunsen flame.
- lithium: crimson, sodium: yellow, potassium: lilac, calcium: orange-red, copper(II): green
Sodium hydroxide solution, a few drops then in excess:
- aluminium, calcium, magnesium: white precipitate (only aluminium hydroxide dissolves in excess)
- copper(II): blue, iron(II): green, iron(III): brown
In a mixture one flame colour can hide another: a trace of sodium's yellow swamps potassium's lilac.
The rest of this lesson and its 11 practice questions are in Plus.
Screen 1 of 4, free to read.
- 11 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards