Paper 2 Chemical Analysis Flashcards
(24 cards)
What does Pure mean?
A substance containing only one type of element or compound
What properties do pure substances have?
- It all melts and solidifies at the same temperature called the melting point
- Boil and condense at the same temperature called the boiling point
What are impure substances?
Substances which do not all melt and boil at the same time, they have a range of boiling and melting temperature points
What are formulations?
Mixtures which are chemically designed to have specific properties.
In chromatography what is the stationary phase and the mobile phase?
Stationary Phase- The absorbent paper
Mobile Phase- The solvent (often water)
What does chromatography do?
Separates the mixture into their components by the solvent dissolving the sample and carrying it up the paper.
(Chromatography) Why do each components in a mixture move to different distances?
Depending whether it is most attracted to the solvent or paper.
Required Practical- Chromatography
- Draw a pencil line on paper
- Put samples of known colourings on the line (A B C D…) along with an unknown (X)
- Dip the paper into a solvent
- Wait for solvent to travel to the top of the paper
- Identify X by comparing to the other known substances
What is the equation for Rf values?
Rf = distance moved by substance / distance moved by substance
Hydrogen gas test
Lit splint should make a squeaky pop when hydrogen is present.
Chlorine gas test
Will turn damp indicator paper white
Oxygen gas test
Relights a glowing splint
Carbon dioxide gas test
When bubbled through limewater it will turn the limewater cloudy
Instrumental Methods
Flame emission spectroscopy
Produces a line spectrum which can be used to identify metal ions and measure the concentration of the metal ions
What can flame tests be used to identify and what are the examples ?
It can be used to identify metal ions. Lithium, sodium, potassium, calcium and copper compounds can be recognised by their distinctive colour which they give off.
Required Practical- Flame Tests
- Heat a nichrome wire in a Bunsen burner and dip it into a concentrated hydrochloric solution to clean it
- Dip the wire into the compound
- Put over Bunsen flame and observe the colour it burns
What are the distinctive colours for copper, calcium, lithium, potassium and sodium?
Copper- Green Calcium- Brick Red Lithium- Crimson Red Potassium- Lilac Sodium- Yellow
Why can a flame test be unreliable?
If a sample contains more than one type of ion then the colour can be masked
What does carbon dioxide do to limewater?
Turn it cloudy
What do solutions of metal compounds contain?
Metal ions
What do some metal ions form when sodium hydroxide solution is added to them?
Precipitates
What are the precipitates formed when sodium hydroxide is added to them (aluminium calcium magnesium copper iron2 iron3)
Aluminium- white Calcium- white Magnesium- white Copper- blue Iron 2- green Iron 3- brown
What happens when a dilute hydrochloric acid and barium chloride are added to a solution containing sulfate ions?
A white precipitate or barium sulfate is produced
What precipitates are produced when halide ions react with silver nitrate and dilute nitric solution?
Silver Chloride is white
Silver Bromide is cream
Silver Iodide is yellow
