Upload
emery-kelley
View
242
Download
0
Embed Size (px)
Citation preview
2j Preparing and analysing
Last lesson - Precipitation reactions
• Reactions that produce an INSOLUBLE SALT
Testing for Cl-, Br- and I- ions
• Add SMALL amounts of silver nitrate solution to salts containing halogen ions that have been dissolved in dilute nitric acid.
Type of ion (dissolved in HNO3(aq))
Result of adding dilute silver nitrate
Cl- White precipitate of silver chloride
Br- Cream precipitate of silver bromide
I- Pale yellow precipitate of silver iodide
Testing for sulphate ions SO42-
(aq)
• Add SMALL amounts of barium chloride solution to salts containing sulphate ions that have been dissolved in dilute hydrochloric acid.
• If sulphate ions are present, a white precipitate of barium sulphate is formed.
Testing for sulphite ions SO32-
(aq)
• Add dilute hydrochloric acid.• Test the gas given off for sulphur dioxide by
passing through pink acidified potassium manganate solution which turns colourless.
Testing for carbonate ions CO32-
(aq)
• You know this one!• Add dilute hydrochloric acid• Test the gas given off for carbon dioxide (turns
limewater “milky”)
Today’s lesson – Gas tests
You know all these already!
Gas tests?
AmmoniaCarbon dioxideChlorineHydrogenOxygenSulphur dioxide
Gas tests?
Ammonia – Turns damp red litmus paper blueCarbon dioxide – turns limewater “milky”Chlorine – bleaches damp litmus paper (white) Hydrogen – lighted splint – “popping sound”Oxygen – relights a glowing splintSulphur dioxide - pink acidified potassium
manganate solution turns colourless
Solubility of different salts
Which dissolve?Salt Soluble?
Sodium chloride
Sodium bromide
Sodium carbonate
Sodium sulphate
Potassium chloride
Potassium bromide
Etc.
When you have finished can you write down some general rules for which slats are soluble/insoluble
Solubility of salts• all common sodium, potassium and ammonium
salts are soluble• ⎯ all nitrates are soluble• ⎯ common chlorides are soluble, except silver
chloride• ⎯ common sulphates are soluble, except barium
and calcium sulphates• ⎯ common carbonates and hydroxides are
insoluble, except those of sodium, potassium and ammonium