Preparation and Tests Flashcards
Test for ammonia
Damp litmus paper blue
Damp universal indicator purple
Calculating electrolysis product amounts
Write out half equation
Calculate coulombs from current
Calculate electron moles (coulombs/faradays)
Scale factor electron moles to get product moles
Calculate mass
Test for chlorine
Bleaches damp litmus paper white
Test for sulphate ions
(Sulphate)+ HCl + Barium Chloride -> barium sulphate precipitate ( white)
Tests for chlorine, bromine and iodine
Test with nitric acid and silver nitrate
Chlorine - White precipitate
Bromine - cream precipitate
Iodine - yellow precipitate
Flame test - Lithium ions
Red flame
Flame test - sodium ions
Orange flame
Flame test -potassium ions
Lilac flame
Flame test - Calcium ions
Brick red flame
Test for positive ions
Metal salt + sodium hydroxide = precipitate in a few cases i.e insoluble metals
Sodium hydroxide + copper ions =
Blue precipitate of copper hydroxide
Sodium Hydroxide + Iron 3 ions =
Orange brown precipitate
Sodium hydroxide + iron 2 ions =
Green precipitate
Sodium hydroxide + ammonium salt =
No precipitate but smell of ammonia
Test for carbonates
Add acid ( preferably nitric) and look for carbon dioxide bubbles
Solubility Rules
All sodium, potassium and ammonium compounds are soluble
All carbonates and hydroxides are insoluble apart from above
All chlorides are soluble except lead chloride and silver chloride
All sulphates are soluble except Barium Sulphate, lead sulphate and Calcium sulphate
Salt preparation
React the alkaline metal with the acid to form a salt mixture - In the cold if carbonate or magnesium, otherwise by heating
Use an excess of the alkali to maximise output
Filter off excess alkali and heat concentrated salt solution .
Test by dipping a glass rod in to see if crystals form.
Alternatively do a titration.
Rules for making salts
If not soluble, use precipitation method
If soluble but not sodium, potassium or ammonium, react with an excess of metal
If soluble and one of three above, use a titration method
