C8 - Chemical Analysis Flashcards
How are pure substances tested?
All pure substances have specific melting/boiling points which can be used to test for them.
What are formulations?
Formulations are mixtures of certain quantities of substances designed to fulfil a specific purpose e,g. fuels/alloys.
Why are mixtures not pure?
Mixtures contain compounds which holds a risk of contamination.
What is chromatography?
Separation of a mixture to identify its constituent substances, e.g, pigments in ink.
Chromatography method
Mobile phase (solvent, e.g, water) moves up the stationary phase (e.g, chromatography paper) due to capillary action.
The substance in the mixture is pulled upwards, with lighter particles moved further up the stationary phase.
Starting line is drawn just above the water line (in pencil, so it doesn’t move). All measurements are made from this.
What are Rf values used for?
The Rf values can be used to compare against that of known substances to identify them.
Equation for Rf value
distance substance moved/distance mobile phase moved
How do you test for hydrogen?
A lit splint produces a squeaky pop, known as the ‘squeaky pop test’.
How do you test for oxygen?
Oxygen will relight a glowing splint.
How do you test for carbon dioxide?
CO2 causes limewater to turn cloudy when bubbled through it.
How do you test for chlorine?
Chlorine will bleach blue litmus paper white.
