Unit 8:Chemical analysis
- Created by: 14pollardr
- Created on: 28-04-18 15:52
View mindmap
- chemical analysis
- flame tests
- if a sample contains a mixture of ions, the colours could be masked
- colours
- copper - Green
- Calcium - Brick red
- lithium - crimson
- Potassium - lilac
- Sodium - yellow
- Chromotography
- involves a stationary phase and a mobile phase
- Rf=distance moved by substance divided by the distance moved by the solvent
- different components have different Rf values
- providing the same temp and solvent are used, the Rf value for a specific compound is constant
- separates mixtures into their constituent components
- pure substances produce a single spot in all solvents
- can be used to identify artificial colours
- pure substances and mixtures
- A pure substance is one made up of just one substance, either an element or a compound
- formulations are mixtures that have been carefully designed to have specific properties
- the components in a formulation are heavily controlled
- impure substances are mixtures
- the melting or boiling points of an element or compound are called its fixed points
- gas tests
- hydrogen - when mixed with air, burns with a squeaky pop
- Chlorine - turns damp indicator paper white
- Oxygen - relights a glowing splint
- Carbon dioxide - When bubbled through lime water, turns it cloudy
- Precipitation of metal ions
- Aluminium (aluminium hydroxide) white precipitate redissolves in excess hydroxide solution
- Calcium (calcium hydroxide) white precipitate
- Magnesium (magnesium hydroxide) white precipitate
- Copper(II) (copper(II) Hydroxide) light blue precipitate
- Iron(II) (iron(II) hydroxide) green precipitate
- Iron(III) (iron(III) hydroxide) brown precipitate
- required practicals
- investigate how paper chromatography can be used to separate.
- 1. draw a start line in pencil on absorbent paper
- 2. Put samples of 5 food colourings and the unknown substance on the line,
- 3. dip the paper into solvent (water)
- 4. wait for the solvent to travel to the top of the paper
- 5. Identify solvent x by cross comparing
- Identify the ions in a single ionic compound using chemical tests
- 1. Heat a piece of nichrome wire in a Bunsen flame and then dip it in concentrated hydrochloric acid o clean it.
- 2.Dip the wire in the compound
- 3.place it into the Bunsen flame and observe the colour
- investigate how paper chromatography can be used to separate.
- metal hydroxides
- AlCl3+3NaOH->Al(OH)3+3NaCl
- CaCl2+2NaOH->Ca(OH)+2NaCl
- MgCl2+2NaOH->Mg(OH)+2NaCl
- Tests for anions
- carbonate test
- sodium carbonate solution in a test tube and limewater in another. add a few drops of hydrochloric acid to the first test tube and collect gas to bubble through the limewater
- sodium carbonate solution will present a white precipitate
- A white precipitate means carbon dioxide present
- halide test
- pour sodium chloride solution, sodium bromide solution and sodium iodide solution into three separate test tubes
- add a few drops of silver nitrate into each test tubes
- sodium chloride solution presents a white precipitate
- Sodium bromide solution presents a cream precipitate
- Sodium iodide solution presents a yellow precipitate
- sulphate test
- pour sodium sulphate into a test tube
- add a few drops of barium chloride solution
- sodium sulphate solution present a white precipitate
- carbonate test
- flame tests
Comments
No comments have yet been made