Topic C8 - Chemical Analysis Flashcards

1
Q

What is PURE SUBSTANCE chemical definition?

A

A substance containing only one element or compound.

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2
Q

What is PURE SUBSTANCE everyday definition?

A

A substance with nothing added to it, e.g milk

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3
Q

What two things will a chemically pure substance do?

A

1) Melt at a specific temperature

2) Boil at a specific temperature

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4
Q

How can you test the purity of a sample?

A

By comparimg its melting or boiling point with that of the pure substance.

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5
Q

What 2 things will impurities in a sample do?

A

1) lower the melting point and increase the melting range

2) increase the boiling point and may also increase the boiling range

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6
Q

Formulations definition?

A

Useful mixtures with a precise purpose.

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7
Q

Examples of FORMULATIONS

A

1) metal alloys
2) medicines
3) fertilisers
4) paints
5) food
6) fuels
7) cosmetics
8) cleaning products

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8
Q

Chromotography defintition

A

An analytical method used to seperate the substances in a mixture. It can be used to identify the substances.

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9
Q

What is the CHROMOTOGRAPHY STATIONARY PHASE?

A

Where the molecules can’t move.

e.g chromotography paper

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10
Q

How can you tell if a substance is pure using CHROMOTOGRAPHY?

A

A pure substance will only ever form one spot in any solvent.

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11
Q

What is the CHROMOTOGRAPHY MOBILE PHASE?

A

Where the molecules can move
(the solvent)
e.g water or ethanol

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12
Q

What does CHROMOTOGRSPHY show?

A

How pure or impure a substance is

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13
Q

What is the CHROMOTOGRAPHY pathway?

A

1) Substances dissolve in the mobile phase
2) The mobile phase moves through the stationary phase
3) Substances that are more soluble or less attracted to the stationary phase move further

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14
Q

What is Rf value?

A

The ratio between the distanced travelled by the dissolved substance, and the distance travelled by the solvent.

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15
Q

Rf value formula

A

Distance travelled by substance
Rf = ——————————-——————
Distance travelled by solvent

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