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Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

Pure substance

A

A substance that contains only one element or only one type of compound.

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2
Q

Why wouldn’t ‘pure’ orange juice be chemically pure?

A

It’s not pure in the chemical sense because it contains different substances mixed together.

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3
Q

Mixture

A

A substance which consists of two or more different substances, which are not chemically bonded/ joined together.

Components of mixtures can be separated easily (without chemical reactions).

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4
Q

Element

A

Contains one type of atom.

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5
Q

Pure element and Mixture of elements
+ Examples

A

Pure element: only contains one type of atom (oxygen. O2)
Mixture of elements: contains different types of atoms (Helium and oxygen. He + O2)

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6
Q

Pure compound and Mixtures of compounds
+ Examples

A

Pure compound: Only one type of compound (Carbon dioxide. CO2)
Mixtures of compound: Different types of compounds, not chemically bonded. (Water+Carbon dioxide. H2O+CO2)

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7
Q

Mixtures of elements and compounds
+ example

A

Air:
Elements O2
Compounds CO2

These are mixed but not chemically bonded.

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8
Q

Pure substances features
+ Examples

A
  • Melting and boiling points are at specific temperatures
    E.g pure water (H2O) has a boiling point of 100 ‘C and a melting point of 0 ‘C
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9
Q

Impure substances features
+ Example

A

-Melting and boiling points are over a range of temperatures
-Impurities in samples cause:
* Higher boiling points
* Lower melting points
E.g Salt Water has a melting point of -2 ‘C and a boiling point of 100.5 ‘C

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10
Q

Physical test?

A

Testing the physical properties of that substance

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11
Q

Formulations
+ Examples

A

A mixture that is always made with the same proportions of the same substances.

Particular mixtures for different things such as: paint, fuel, medicine, etc.

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12
Q

Chemical test

A

React the substance with another chemical to figure out the substance.

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13
Q

Explain formulations

A

Mixtures which have been made using a specific formula so they contain precise amounts of different components.

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14
Q

Chemical analysis (also known as analytical chemistry) is about?

A

Methods we use to Identity, Separate,and Quantify different substances.

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15
Q

Separating examples

A

-Filtration
-Chromatography
-Distillation

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16
Q

True or False
Pure substances melt at specific temperatures.

A

True

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17
Q

Senku is given a substance.
How would he work out if it is pure water, (a substance that only contains H2O)?

A

Freeze it, see if it’s freezing point is 0 ‘C
Boil it, see if it’s boiling point is 100 ‘C

18
Q

Senku tests the melting point of Salon.
How can he work out if the substance is pure or impure?

A

If the melting point ranges over temperatures (and does not have a specific melting point), then it is impure.

Range of temperature means that it starts melting at one temperature and finishes fully at another temperature.

19
Q

Formulations are made from…

A

…precise amounts of different components, and each component has a particular/specific function.

20
Q

Test for Carbon Dioxide gas.

A

Turns limewater ( Ca(OH)2 ) milky.

21
Q

Test for Oxygen

A

Relights a glowing splint.

22
Q

Rf value.

A

Distance traveled by the substance
____________________________________
Distance traveled by the solvent

23
Q

What will happen when you do chromatography with a pure substance.

A

There will only be a single spot, so we can calculate a specific Rf value.

24
Q

What changes the Rf value?

A

Different type of paper
Different solvent

25
Q

Why would the Rf value change when changing the solvent or type of paper?

A

Because the mobile and stationary phases of the substance changes.

26
Q

What is paper chromatography used for?

A

To separate mixtures of soluble substances in liquids.

27
Q

Why don’t we use pen for the baseline?

A

Pen ink would dissolve in the solvent and move up the paper.

28
Q

Chromatogram

A

The results of separating mixtures by chromatography.

29
Q

What is the mobile phase in paper chromatography?

A

The mobile phase refers to the molecules that can move.
It is the solvent in paper chromatography.

30
Q

Senku carried out a paper chromatography experiment.
Why did chemical A move more than all the others?

A

A substance which is more soluble in the mobile phase, will spend more time in the mobile phase. This means it will move faster and travel a further distance up the paper.

31
Q

How can we tell when two substances are the same in paper chromatography?

A

They have:
-Produced the same number of spots
-The spots have the same colour
-The spots have the same Rf value

32
Q

What is the Rf value and what does it show?

A

The Rf value is between 0 and 1
The closer to 1, the more the substance is attracted to the mobile phase.
The closer to 0, the more attracted the substance is to the stationary phase.

33
Q

What would a chromatogram of a pure substance look like?

A

There will be a single spot, so we can calculate a specific Rf value.

34
Q

What is chromatography?

A

A chemical analysis that is used to separate substances in a mixture.

35
Q

Should the baseline be submerged in water?

A

No

36
Q

What are the common solvents used for paper chromatography?

A

Ethanol
Water

37
Q

Where would the
-insoluble substances
-substances with a relatively slow rate of travel
-substances with a relatively fast rate of travel
…be located?

A

Insoluble: On the baseline
Slow rate: Near to the baseline
Fast rate: Further from the baseline

38
Q

What is the mobile phase in paper chromatography?
(An example)

A

The solvent.

39
Q

What is the stationary phase in paper chromatography?
(An example)

A

The paper

40
Q

What is the test for Chlorine gas?

A

Damp blue litmus paper turns red and then bleached white.

41
Q

What is the test for hydrogen gas?

A

A lit splint reacts with hydrogen and produces a squeaky pop when it explodes.

Chemistry (6 decks)

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