Chemical Analysis Flashcards
What is a pure substance in chemistry
A substance is a single element or compound that is not mixed with any other substance
What is a pure substance in everyday language
A substance that has had nothing added to it
What is a formulation
A mixture that has been designed as a useful product, with carefully measured components so the product has desired and required properties.
What does Paper Chromatography do
Separates the different dyes in an ink
Describe paper chromatography method (7 steps)
1- take filter paper and draw line in pencil near bottom (base line)
2 - add sample of ink to baseline
3 - Fill beaker with shallow amount of solvent
4 - Place filter paper into solvent
5 - Don’t submerge ink in solvent
6 - Place lid on top of beaker to stop the solvent evaporating
7 - Wait for solvent to seep up paper, dyes will dissolve in solvent and move up with it at different rates
8 - Take paper out and leave to dry
What happens to un soluble substances in paper chromatography
Stay on the base line
What is the mobile phase
Substance the molecules can move in (solvent)
What is the stationary phase
Substance the molecules can’t move in (paper)
Why do more soluble substances move up further
Spend more time in the mobile phase, so move faster
Less soluble are more attracted to the paper and spend more time in the stationary phase
How to calculate Rf value
Distance travelled by substane / distance travelled by solvent
Test for hydrogen
- Burning splint held at the open end of a test tube of the gas
- Hydrogen burns rapidly with a pop sound
Test for oxygen
- Glowing splint inserted into a test tube of the gas
- The splint relights in oxygen
Test for carbon dioxide
- Use aqueous solution of limewater, will turn cloudy when co2 is bubbled through it
Test for chlorine
- Damp litmus paper bleaches and turns white in presence of chlorine gas
What do lithium compounds result in during flame test
Crimson flame
What do sodium compounds result in during flame test
Yellow flame
What do potassium compounds result in during flame test
Lilac flame
What do calcium compounds result in during flame test
Orange/red flame
What do copper compounds result in during flame test
Green flame
What solutions form white precipitate and when
When sodium hydroxide solution is added,
Aluminium
Calcium
Magnesium
But magnesium hydroxide precipitate dissolves in excess sodium hydroxide solution
When sodium hydroxide is added, what colour precipitate does copper (ii) form
Blue
When sodium hydroxide is added, what colour precipitate does iron (ii) form
Green
When sodium hydroxide is added, what colour precipitate does iron(iii) form
Brown
Test for carbonates
Will react with dilute acids to form co2, which can be identified using limewater
Test for halides
Produces precipitates with silver nitrate, if in the presence of dilute nitric acid
What colour precipitate is silver chloride
White
What colour precipitate is silver bromide
Cream
What colour precipitate is silver iodide
Yellow
Test for sulphates
Produce a white precipitate with barium chloride solution in the presence of HCL
Give an example of an instrumental method of analysing elements and compounds
Flame emission spectroscopy
Explain briefly how to carry out flame emission spectroscopy
Place sample into a flame and the light given out is passed through a spectroscope.
The output is a line spectrum that can be analysed to identify metal ions and their concentration
