Purity, Formulations and Chromotography

What are pure substances?

• single element or compound

• worked out by looking at melting and boiling points of samples

• closer the values of oyur experiment are, the purer a sample is

• e.g Water, copper sulfate, glucose, sodium chloride and oxygen gas

What are the effects of impurities in a sample?

• decreases melting point

• increases boiling point

• increases rate of temperatures

What are formulations?

• mixtures of chemicals that are designed to create useful products

• e.g fertilisers, cleaning agents, medicines, fuels and metal alloys

What is chromotography?

a process that separates a mixture into its different components

What are the 2 phases?

• Substances are picked up and carried by a mobile phase (liquid or gas)

• The mobile phase then moves through a stationary phase (solid or viscous liquid)

• If a substance moves far if it's more attracted to the mobile phase

• ubstance doesn't move far if it's more attracted to the stationary phase

What are steps in paper chromotagrpahy?

• dip chromatography paper into solvent

• solvent travels up the chromotography paper

• as solvent moves, it picks up the substances being tested and carries them up the chromatography paper

What are the phases in chromotatogrophy?

• Stationary- chromotography paper

• Mobile- solvent

Why do we use chromatograms?

• to identify compounds in mixtures by calcualting Rf values

• Rf= distanceby substance/ distance by solvent

What is the required practical for paper chromatography?

• Use a pencil to draw a horizontal line near the bottom of the chromatography paper

• On this ‘start line’, put samples of known food colourings (A - D) alongside an unknown substance (X)

• Place the paper in a beaker containing a small volume of solvent.

• Wait for the solvent to travel to near the top of the paper

• By comparing spots produced by X with those produced by A - D, it should be possible to identify the unknown substance

Hydrogen test?

• test is done with burning splint

• result is squeaky pop

CO₂ test?

• test is done with bubbles, gas limewater

• result is limewater goes cloudy

• transfer gas using delivery tube

Chlorine test?

• test is inserting damp litmus paper into a test tube containing a chlorine gas

• result is litmus paper will bleach red to white

Oxygen test?

• test is inserting glowing split into test tube containing oxygen

• the result is the splint relighting