8.1 Purity, formulations and chromotography Flashcards
(11 cards)
What is a pure substance?
A single element (e.g., pure silicon rod) or compound (e.g. sodium chloride) which is not mixed with any other substance.
What are the chemical properties of pure and impure substances? (2)
- Pure substances have a specific boiling and melting point.
- Impure substances melt and boil over a range of temperatures.
What is a formulation?
A complex mixture that has been designed as a useful products.
How is a formulation made?
The quantity of each components in the formulation is carefully measured so that the product has the properties needed.
What are some examples of formulations? (≥2)
- Fuels
- Cleaning products
- Paints
- Medicines
- Alloys
- Fertiliser
- Food
What is the use of paper chromatography?(1)
Enables the separation of different substances in a mixture due to / based on their different solubilities.
What is the stationary and mobile phase in paper chromatography? (2)
- Stationary: the paper - does not move
- Mobile: the solvent - moves
How can a pure and impure compounds be detected in paper chromatography? (2)
- Pure: produce single spot in all solvents
- Mixture: may separate into different spots depending on solvent
What does the distance travelled by a spot in paper chromatography determine? (1)
The further up the spot travels, the more soluble it is in that solvent.
Why do we draw our starting line in pencil in paper chromatography? (1)
Pencil is insoluble in the solvents used - if pen ink was used, it would travel up with the solvent.
What is the equation for Rf value?
Rf = distance moved by substance / distance moved by solvent
