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Chemistry _Amma > Elements Compound & mixtures > Flashcards

Elements Compound & mixtures Flashcards

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1
Q

What does the term ‘pure’ mean in chemistry?

A

A single element or compound with no other substances added.

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2
Q

What is a cooling curve used to show?

A

Influence of impurities

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3
Q

What is the relative atomic mass of an element?

A

Larger number on the Periodic Table

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4
Q

What is an empirical formula?

A

Simplest whole number ratio of atoms of each element in a molecule

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5
Q

How is the percentage by mass of an element in a compound calculated?

A

Percentage composition formula

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6
Q

What happens chemically when a mixture is formed?

A

The chemicals are physically mixed but not chemically combined.

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7
Q

What kind of temperature data can be used to produce a graph for a liquid?

A

Cooling and freezing

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8
Q

How is the empirical formula related to the molecular formula?

A

The empirical formula can be deduced from the molecular formula

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9
Q

What is filtration used for?

A

Separate undissolved solid from a mixture

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10
Q

What is the boiling point of pure water?

A

100°C

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11
Q

What does a horizontal part in a cooling curve indicate?

A

Sharp melting point

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12
Q

What is the empirical formula of hexane with the molecular formula C6H14?

A

C3H7

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13
Q

How can melting and boiling points help distinguish pure substances from mixtures?

A

Pure substances have specific, sharp melting/boiling points; mixtures have ranges.

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14
Q

How does a cooling curve for an impure substance differ from that of a pure substance?

A

Gradual decrease in temperature

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15
Q

What is the empirical formula of the ionic compound?

A

Empirical formula is based on ions and charges

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16
Q

What does a melting point apparatus allow you to do?

A

Slowly heat up a small amount of the sample

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17
Q

What is a common topic for percentage change calculations?

A

Calculate Percentage Change

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18
Q

How is the purity of a sample determined using melting point data?

A

Closer measured value to actual melting point indicates higher purity

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19
Q

What is relative molecular mass?

A

Average mass of atoms of a molecule relative to carbon-12

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20
Q

According to the Law of Conservation of Mass, what remains the same in a balanced chemical equation?

A

Sum of relative molecular masses

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21
Q

Can the empirical formula and molecular formula be the same?

A

Yes

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22
Q

How to determine the empirical formula of a compound in a 3D lattice structure?

A

Identify ions, balance charges to zero

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23
Q

What are the steps to determine the empirical formula of a compound?

A

Identify ions, balance charges, determine ratio

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24
Q

What is placed above the beaker in filtration?

A

Filter paper

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25
Q

What will pass through the filter paper in filtration?

A

Small liquid particles

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26
Q

By what means can substances in a mixture be separated?

A

Physical means.

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27
Q

What is an example of a pure substance?

A

Pure water (H2O).

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28
Q

For what purpose is melting point analysis routinely used?

A

To assess the purity of drugs.

29
Q

How do you calculate the relative formula mass?

A

Add up atomic masses in the formula

30
Q

What is the empirical formula related to?

A

2.1.3 Empirical Formula

31
Q

What should you do after calculating the percentage by mass to convert it into a percentage?

A

Multiply by 100

32
Q

What is used to separate a liquid and soluble solid from a solution?

A

Heating, evaporation, and condensation.

33
Q

What is Fractional Distillation used for?

A

Separating miscible liquids

34
Q

What is chromatography used for?

A

Separate substances and provide information

35
Q

What is the process by which the solvent moves up the paper in paper chromatography?

A

Capillary action

36
Q

What is the stationary phase in Thin-Layer Chromatography?

A

Thin layer of inert substance (e.g. silica)

37
Q

What happens in the condenser?

A

Vapour cools and condenses into pure liquid.

38
Q

Which substance is more likely to evaporate out of a fractionating column?

A

Substance with lower boiling point

39
Q

Why do different substances in paper chromatography spread apart?

A

Different solubilities

40
Q

How does the mobile phase move in Thin-Layer Chromatography?

A

Solvent

41
Q

What is collected in the beaker?

A

The pure liquid.

42
Q

What happens when a mixture of water and ethanol is heated to 78 ºC?

A

Ethanol boils and distills out

43
Q

How do substances with higher solubility behave in paper chromatography?

A

Travel further

44
Q

What is the formula to calculate the retention factor (Rf) value?

A

Distance moved by compound ÷ Distance moved by solvent

45
Q

What’s left behind after all the water is evaporated from the solution?

A

Only the solid solute.

46
Q

What are the two phases used in all chromatography techniques?

A

Mobile phase and stationary phase

47
Q

What will pure substances produce on the chromatogram?

A

One spot

48
Q

How does Fractional Distillation work?

A

By heating to the boiling point of the substance with the lowest boiling point

49
Q

How are components separated in chromatography?

A

Different solubilities in a solvent

50
Q

How will a mixture appear on the chromatogram?

A

Separate spots for different components

51
Q

What happens to the pure water during the separation process?

A

It evaporates, producing a vapour.

52
Q

When should heating be stopped when separating water and ethanol?

A

When the temperature reaches 100 ºC

53
Q

In paper chromatography, what is the mobile phase?

A

Solvent

54
Q

What does an impure substance produce on the chromatogram?

A

More than one spot

55
Q

Where does the vapour go after it rises through the neck of the round bottomed flask?

A

Through the condenser.

56
Q

Why is a fractionating column used in Fractional Distillation?

A

To increase surface area for contact with evaporated substances

57
Q

Why is a pencil line used in paper chromatography?

A

Prevent ink from running into chromatogram

58
Q

What determines the speed at which substances move in paper chromatography?

A

Affinities for phases

59
Q

Why are Rf values important in TLC?

A

To identify components of mixtures

60
Q

How do chemists use Rf values to identify unknown substances?

A

Compare with Rf values of known substances

61
Q

What are the units of Rf value?

A

No units (ratio)

62
Q

What will identical substances produce on the chromatogram?

A

Identical chromatograms

63
Q

What is Gas Chromatography used for?

A

Separating a mixture of gases

64
Q

Which compounds were present in equal amounts?

A

B and C

65
Q

What is the mobile phase in Gas Chromatography?

A

Unreactive carrier gas e.g nitrogen

66
Q

What is the stationary phase in Gas Chromatography?

A

Thin layer of unreactive liquid e.g silica or aluminium powder

67
Q

What information does a gas chromatogram provide?

A

Number of peaks, height of peaks, position of peaks

68
Q

How is a chromatogram generated in Gas Chromatography?

A

By a computer

69
Q

How is retention time defined in Gas Chromatography?

A

The time it took for a compound to move through the column

Chemistry _Amma (8 decks)

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