Chemsitrh - Chemical Analysis Flashcards
Colour of lithium ion flame
Bright red
Colour of sodium ion flame
Yellowy orange
Colour of potassium ion flame
Lilac
Colour of calcium ion flame
Brick red
Colour of copper ion flame
Blue green
Test with sodium hydroxide what colour precipitate is made from copper 2 ion
Blue precipitate
Test with sodium hydroxide what colour precipitate is made from iron 2 ion
Green precipitate
Test with sodium hydroxide what colour precipitate is made from iron 3 ion
Brown precipitate
Test with sodium hydroxide what colour precipitate is made from ammonium (and what other step is needed)
- mixture needs to be warmed
- no precipitate, but stinky smelling gas that turns damp red litmus paper blue
Test with sodium hydroxide what colour precipitate is made from aluminium ion
White precipitate
Test with sodium hydroxide what colour precipitate is made from calcium ion
White precipitate
How to tell difference between calcium and aluminium ions in sodium hydroxide?
Aluminium dissolves in excess whereas calcium doesn’t
How do you test for sulphates?
Mix BaCl2 with HCl
Add new acidified BaCl2 to sulphate/ unknown substance
White precipitate - barium sulphate should be formed
Testing for halide ions and what colours they turn
- Add HNO3 to AgNO3
- Add no more than 1cm3 of halide and then add acidified AgNO3 solution to halide
- then silver chloride should turn white precipitate
- silver bromide should be a cream precipitate
- silver iodide should be a yellow precipitate
Testing for carbonates
- add some HCl to 1cm3 of the ‘carbonate’
- then test it by bubbling it through limewater
what happens when a carbonate is bubbled through limewater?
it turns it cloudy and makes little lumps of solid, and afterwards it should turn colourless again
What is limewater?
Calcium hydroxide solution
Why does the reaction between calcium carbonate and sulphuric acid stop effervescent after a few seconds?
As a protective coating of insoluble calcium sulphate is formed around the calcium carbonate - coating any remaining calcium carbonate and preventing any further reaction with sulphuric acid and hence no more calcium sulphate is formed
Equation (with state symbols) between carbon dioxide and limewater
Ca(OH)2 (aq) + CO2(g) —> CaCO3 (s) + H2O (l)
Equation for the 2nd reaction between carbon dioxide and limewater
CaCO3 (s) + H2O (l) + CO2 (g) —> Ca(HCO3)2 (aq)
