C2. Purity and separation Flashcards
What is relative atomic mass?
Number of protons
What is relative formula mass?
Number of protons and neutrons
What is the empirical formula?
Simplest whole number ratio of atoms
What does pure mean?
consists of just one element or compound
What is an alloy?
Mixture of metal with one or more elements
What is a solute?
The substance which dissolves
What is the solvent?
substance solute dissolves in
What can filtration be used for?
An insoluble substance in the solid state and a substance in a liquid state
How does filtration work?
Separates insoluble substance from liquid with filter paper
What can crystallisation be used for?
A solvent and solute
How does crystallisation work?
Slowly evaporate solution until crystals form then cool down
What does simple distillation separate?
A solvent from a solution
How does simple distillation work?
When solution is heated, the solvent boils but the solute doesn’t as they have different boiling points. Solvent can be condensated back down is needed, if not open container
What does fractional distillation separate?
two or more substances from a mixture in the liquid state
How does fractional distillation work?
When the mixture is heated: vapours rise through a column which is hot at the bottom, and cooler at the top. vapours condense when they reach a part of the column that is below the temperature of their boiling point.
What stops two or more substances rising at the same time?
Fractionating column - the substances with lower boiling points reach the top of the column, while those with higher boiling points condense and fall back down.
What phases does chromatography rely on?
Stationary and mobile
What is the stationary phase?
Does NOT move
What is the mobile phase?
Does move
What are the three types of chromatography?
Paper
Thin-Layer
Gas
What is the stationary phase in paper chromatography?
Absorbent paper
What is the mobile phase in paper chromatography?
Solvent in the liquid state
What is paper chromatography used for?
Separate coloured substances in ink or sweets
How is thin-layer chromatography different from paper?
The stationary phase is a thin layer of silica or alumina powder spread of plate of glass or plastic
What is stationary phase in gas chromatography?
Stationary phase is silica or alumina powder packed into metal column
What is mobile phase is gas chromatography?
unreactive carrier gas such a nitrogen
Why is thin-layer chromatography the best type?
Quickest
Most sensitive - smaller sample can be used
Large range of stationary phases and solvents to use
