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Chemistry - S1 > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

What is an element?

A

An element is a substance that is made of only one type of atom.

Elements are substances that cannot be decomposed into simpler substances

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2
Q

What are molecules?

A

Molecules are made up of two or more atoms covalently bonded together.
Molecules can be formed by two atoms of the same element, or by atoms from two or more different elements.

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3
Q

What are the properties of metals?

A

Shiny, sonority, High density, electrical and thermal conductor, malleable, ductile, usually high melting and boiling point

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4
Q

What are the Properties of Non metals

A

Dull, low density, brittle, electrical and thermal insulators and have a low melting and boiling point

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5
Q

What is a compound

A

A compound is a substance that consists of two or more elements that are chemically bonded together

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6
Q

What is a mixture?

A

Contains two or more substances which are not chemically bonded together and are easily separated

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7
Q

What is a pure substance?

A

Made up of a single element or compound
•Is not mixed with any other substance
•Has a definite melting and boiling point

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8
Q

What is a formulation?

A

A mixture that has been designed as a useful product
•Made by mixing several different substances in carefully measured quantities
•To ensure the products has required properties
•E.g. medicines, fertilizers

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9
Q

What is a solute?

A

a solid that dissolves in the solvent

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10
Q

What is a solvent?

A

the liquid that the solid dissolves in

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11
Q

What is the solution?

A

a mixture of the dissolved solute and solvent

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12
Q

What does soluble mean?

A

a substance that dissolves

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13
Q

What does insoluble mean?

A

a substance that does not dissolve

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14
Q

What does filtration do?

A

Separates an insoluble solid from a solution

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15
Q

What is the residue?

A

It is an insoluble solid that is caught in the filter paper when the solution is filtered through the filter funnel

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16
Q

What is the filtrate?

A

The liquid which passes through the filter paper and is collected as it drips out of the spout of the funnel.

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17
Q

What is the distillate?

A

pure liquid which collects at the lower end of the condenser

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18
Q

What does miscible mean?

A

liquids that do mix e.g. alcohol & water

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19
Q

What does immiscible mean?

A

Liquids that do not mix e.g. oil & water

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20
Q

Name 3 - Separating mixtures of 2 liquids techniques

A

Separating funnel
Simple distillation
Fractional distillation

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21
Q

Diagrams of techniques of separating two liquids

A

Look in book and also think about labels

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22
Q

What does potable mean?

A

Water that is safe to drink.

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23
Q

Can potable water be obtained from fresh or seawater?

A

Potable water can be obtained from fresh water or seawater but the water source needs to be treated before it is fit to drink.

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24
Q

For potable water to be obtained Fresh water must go through which 3 processes?

A

Filtration, Sedimentation and Chlorination

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25
Q

What does Filtration do?

A

Removes insoluble solids
e.g. stones, soil, leaves

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26
Q

What does Sedimentation do?

A

Al2(S04)3, Aluminium sulphate clumps tiny particles together. New large particles settle out at bottom.

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27
Q

What does Chlorination do?

A

Chlorine gas is bubbled into kill microbes and sterilise water

28
Q

Describe Filtration when used for obtaining potable freshwater?

A

The water is sprayed onto specialized layers of sand and gravel called filter beds.

Different-sized insoluble solids are removed as the water trickles through the filter beds; the sand and gravel acts like filter paper.

The filter beds are then cleaned every so often by pumping clean water through the filter backwards.

29
Q

Describe Sedimentation?

A

In a sedimentation tank, aluminium sulphate is added to clump tiny particles together to make larger particles.

Then water is passed through a fine filter such as carbon granules, to remove very small particles.

30
Q

Describe Chlorination?

A

Chlorine gas is bubbled into the water to kill microbes and sterilise the water.

31
Q

What process is used to obtain potable water from seawater.

A

Desalination

32
Q

Describe Desalination?

A

Desalination removes dissolved substances from sea water and is carried out by distillation.

33
Q

How much does desalination cost and how do countries get around it?

A
  • Expensive as a large amount of energy is needed to boil water.
  • Many countries use solar power to reduce costs.
34
Q

Explain separating technique - Separating Funnel

A

Works by separating a mixture of immiscible liquids

The lower liquid layer is drained off carefully using a tap.

Examples: oil (upper layer) and water

35
Q

Explain separating technique - Simple distillation

A

Works by separating a solution which contains a mixture of a solid (a solute) and a liquid (a solvent).

The liquid is boiled off in a flask then its vapour is cooled, using a Liebig condenser, so that it condenses back to the liquid.

The collected liquid is called the distillate.

Hence 2 processes are involved: evaporation and condensation.

36
Q

Explain separating technique - Fractional Distillation

A

Same as simple distillation but each but very specific so each liquid boils at separate temps

37
Q

How do you test for water?

A

Anhydrous copper (II) sulfate is white and can be used to test for the presence of water (as it will turn blue in the presence of water).

Anhydrous copper sulfate + water —> hydrated copper sulfate
CuSO4 + 5H2O —> CuSO4.5H2O
White blue

38
Q

Method for carrying out paper chromatography?

A
  1. Using a pencil, draw a base line on the chromatography paper around 1-2cm from the bottom. Use pencil as it will not dissolve in the solvent
    1. Using a capillary tube, place a spot of the substance to be analysed on the base line. When this is dry add another spot on top to make it concentrated.
    2. Place the paper in a beaker with the solvent at the bottom. The pencil line and spots must be above the level of the solvent so that the spots do not dissolve into the solvent in the beaker.
    3. The solvent travels up the paper.
    4. When the solvent is near the top, take the paper out of the solvent and mark the level that the solvent reached This is the solvent front.
    5. Leave the paper to dry. The mixture should have separated into different components, which are seen as spots on the paper.
39
Q

What is chromatography used for?

A

Chromatography is used for separating and analysing mixtures of soluble substances.

40
Q

How do the substances separate during chromotography?

A

Components in a mixture are attracted to both phases and become distributed between them. It is the relative strength of the attraction of each phase for the components which is important.

Different components travel at different rates depending on their strength of attraction to each phase.

A component strongly attracted to the stationary phase (the paper) will be largely dissolved in it, and will be held back.

One with a relatively strong attraction for the mobile phase (the solvent), will be largely dissolved in it, and will move along quickly in it.

41
Q

What is the solvent front on chromatography paper?

A

The further point the solvent rises too

42
Q

How to you calculate the retardation factor of each substance using chromatography paper?

A

Rf values: Retardation factor = Distance moved by spot/ Distance moved by solvent

43
Q

Diagram of chromatography paper

A

Look in book

44
Q

What is a precipitate?

A

A precipitate is a solid formed when two solutions are mixed together

45
Q

What do you call a solid turning into a liquid?

A

Melting

46
Q

What do you call a liquid turning into a gas?

A

evaporation

46
Q

What do you call a gas turning into a liquid?

A

condensation

47
Q

What do you call a liquid turning into a solid?

A

frezzing

48
Q

What do you call a solid turning into a gas?

A

sublimation

49
Q

What do you call a gas turning into a solid?

A

disposition

50
Q

Ionic equation for neutralisation?

A

OH- (aq) + H+ (aq) = H2O (l)

51
Q

Explain the method for Testing for positive ions with a bunson burner:

A

Method:
1. Dip nichrome wire into concentrated hydrochloric acid
2. Dip the wire into the test solid
3. Place nichrome wire in the Blue Bunsen flame
4. Note the colour of the flame

52
Q

Explain the method for Testing for positive ions with precipitate reactions:

A
  1. Make a solution of the salt to be tested (dissolve solute in water)
  2. Place about 5cm3 of the metal ion solution into a test tube and add a few drops of NaOH solution
  3. Record the colour of the precipitate
  4. Add NaOH until it is in excess and record the effect
53
Q

What colour will the Bunson flame burn in a positive test for -

Lithium
Sodium
Potassium
Calcium
Copper (II)

A

Crimson Red
Orange
lilac
brick- red
green-blue

54
Q

Result on adding dilute NaOH or NH3 solution for -

Cu2+ Copper (II)
Fe2+ Iron (II)
Fe3+ Iron (III)
Mg2+ Magnesium
Al3+ Aluminium
Zn2+ Zinc

A

Blue ppt of copper (II) hydroxide

Green ppt of iron (II) hydroxide

Brown ppt of iron (III) hydroxide

White ppt of magnesium hydroxide

White ppt of aluminium hydroxide

White ppt of zinc hydroxide

55
Q

Effect of adding excess NaOH solution for -

Cu2+ Copper (II)
Fe2+ Iron (II)
Fe3+ Iron (III)
Mg2+ Magnesium
Al3+ Aluminium
Zn2+ Zinc

A

Blue ppt remains

Green ppt remains

Red-brown ppt remains

White ppt remains

White ppt dissolves and a colourless solution is produced

White ppt dissolves and a colourless solution is produced

56
Q

Effect of adding excess NH3 solution for -

Cu2+ Copper (II)
Fe2+ Iron (II)
Fe3+ Iron (III)
Mg2+ Magnesium
Al3+ Aluminium
Zn2+ Zinc

A

Blue ppt dissolves and a deep blue solution is produced

Green ppt remains

Brown ppt remains

White ppt remains

White ppt remains

White ppt dissolves and a colourless solution is produced

57
Q

Example of ionic equation for the precipitation reaction to test for the presence of cations:

A

Fe2+(aq) + 2OH-(aq) –> Fe(OH)2(s)
Fe3+(aq) + 3OH-(aq) –> Fe(OH)3(s)

58
Q

Method for testing for halides:

A
  1. Make a solution of the halide salt e.g. if soluble- add a spatula of solid and dissolve in water
    If insoluble- add a spatula of solid to nitric acid
  2. To (1cm3 of) the solution add (1cm3 of) dilute nitric acid.
  3. Add a few drops of silver nitrate solution.
59
Q

Result on adding silver nitrate solution to find halide ions -

Chloride
Bromide
Iodide

A

White ppt of silver chloride
Cream ppt of silver bromide
Yellow ppt of silver iodide

60
Q

Example of the ionic equation for testing for halides:

A

Ag+(aq) + Cl-(aq) –> AgCl(s)

61
Q

Explain the method for testing for sulfate ions:

A

Method:
1. Make a solution of the halide salt e.g.
if soluble- add a spatula of solid and dissolve in water
If insoluble- add a spatula of solid to nitric acid
2. Add a few drops of barium chloride solution

62
Q

Example of a positive test for sulfate ions

A

If a white ppt forms, the solid contains sulfate ions.

63
Q

Explain the method to test for carbonate ions:

A
  1. Add dilute hydrochloric acid to the solid
  2. Test the gas produced with limewater
63
Q

Ionic equation for testing for sulfate ions:

A

Ba+(aq) + SO42-(aq) –> BaSO4(s)

64
Q

Ionic equation for testing for carbonate ions:

A

CO32-(aq) + H+(aq) –> CO2(g) + H2O(l)

Chemistry - S1 (8 decks)

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