8.1 Purity, Formulations & Chromatography

What is a pure substance?

Substance that contains only one type of element or compound

What is a mixture?

Substance that contains two or more elements or compounds not chemically bonded together

Mixtures have a _______ of ________ and _________ points while _____ __________ have fixed/sharp __________ and _________ points.

• range

• melting

• boiling

• pure substances

• melting

• boiling

Impurities cause the melting point of a substance to _________ and the boiling point of a substance to __________.

• decrease

• increase

Is this a pure substance or a mixture?

Pure substance

This is a ______ ___________ because it has a ______ melting point.

• pure substance

• fixed

Is this a pure substance or a mixture?

Mixture

This is a ________ because it melts over a _______ of different temperatures.

• mixture

• range

What is a formulation?

A mixture that has been designed to have useful properties.

Formulations are made by mixing the components carefully in ___________ quantities to ensure that the product has the required properties.

measured

What are some examples of formulations?

• Fuels

• Fertilisers

• Paints

Why should the line be drawn in pencil in chromatography?

Pencil is insoluable so it won’t affect the chromatogram.

Which of the inks are pure substances?

• Red

• Blue

• Yellow

Which of the inks are impure substances?

Brown

How many spots does a pure substance produce on a chromatogram?

1

How do you calculate an R_f value?

distance travelled by substance / distance travelled by solvent

When measuring the distance travelled by the substance you go from the pencil line to the _________ of the spot.

middle

The more attracted a substance is to the stationary phase, the closer to _ its R_f value is going to be.

0

The less attracted a substance is to the stationary phase, the closer to _ its R_f value is going to be.

1

The more attracted a substance is to the mobile phase, the closer to _ its R_f value is going to be.

1

The less attracted a substance is to the mobile phase, the closer to _ its R_f value is going to be.

0

What is the range that an R_f value can be?

0 - 1

A value of 0 for the R_f value indicates that the substance has no attraction to the _______ phase — it is ___________.

• mobile

• insoluble

In chromatography, separation depends on the ___________ of substances between the phases.

distribution

What is the stationary phase?

The phase that doesn’t move — e.g. paper.

What is the mobile phase?

The phase that moves — e.g. solvent.