C8 - Chemical Analysis

How can you test for a pure substance?

Using its very specific melting / boiling point

What is a formulation?

A mixture of certain quantities of substances designed to fulfil a specific purpose eg paints, fuels, alloys, fertilisers

Chromotography

The seperating of a mixture to identify its constituent substances e.g. pigments in ink, drugs in a urine sample

What happens in the first stage of chromotography?

The mobile phase (solvent eg water) moves up the stationary phase (eg chromotography / filter paper) due to capillary action

What happens in the second stage of chromotography?

Capillary action pulls the substances in the mixture upwards, with the lighter particles being moved further up the staitionary phase

Where is the starting line drawn during chromatography?

Just above the water line, in pencil (so it isnt dissolved by the solvent). All measurements are made from this

How are Rf values used?

To compare those in the sample against the Rf values of known substances to identify them

Rf Value =

Rf value = distance substance moved / distance mobile phase moved

How do you test for Hydrogen?

Lit splint produces a squeaky pop

How do you test for Oxygen?

Will relight a glowing splint

How do you test for Carbon Dioxide?

Causes limewater to turn cloudy when bubbled through it

How do you test for Chlorine?

Bleaches blue litmus paper