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Chemistry IGCSE > Unit 12 - Experimental techniques and chemical analysis > Flashcards

Unit 12 - Experimental techniques and chemical analysis Flashcards

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1
Q

Common variables in chemistry

A
  • Time
  • Temperature
  • Mass
  • Volume
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2
Q

Units of time

A
  • Seconds (s)
  • Minutes (min)
  • Hours (h)
  • Days (d)
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3
Q

Units of temperature

A
  • Celsius (˚C)
  • Kelvin (˚K)
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4
Q

Units of mass

A
  • Kilogram (kg)
  • Gram (g)
  • Tonne (t)
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5
Q

Units of volume

A
  • Cubic meters (m^3)
  • Cubic decimeters (dm^3)
  • Cubic centimetres (cm^3)
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6
Q

Apparatus to measure time

A
  • Stopwatch
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7
Q

Apparatus to measure temperature

A
  • Thermometer
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8
Q

Apparatus to measure mass

A
  • Mass balance
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9
Q

Apparatus to measure volume

A
  • Burettes
  • Volumetric pipettes
  • Measuring cylinders
  • Gas syringes
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10
Q

Measuring cylinder

A
  • Used for volume of liquids
  • Units of measurements are usually in cm^3
  • Increments are usually in every 0.2 or 0.1cm^3
  • Not very accurate for small values
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11
Q

Volumetric pipette

A
  • Used for volume of liquids
  • Transfers small volumes of liquids from one vessel to another
  • Accurate for smaller volumes
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12
Q

Burette

A
  • Used for volume of liquids
  • Long tube that usually stores up to 50cm^3
  • Very accurate
  • Increments of 0.1cm^3
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13
Q

Gas syringes

A
  • Used for volume of gases
  • Inner chamber with a ground glass surface around a ground glass surface
  • Gas-tight seal
  • Can hold between 500cm^3 - 0.25cm^ and be accurate up to 0.01cm^3 depending on size
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14
Q

Solvent

A

Usually a liquid which dissolves a solute

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14
Q

Solute

A

The substance being dissolved by the solvent

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15
Q

Suspension

A

Mixture of substances, usually a liquid or solution with an insoluble solid due to separation of solid substances through solvents

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15
Q

Residue

A

The insoluble portion of the mixture/suspension

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16
Q

Filtrate

A

The soluble portion of the mixture/suspension

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17
Q

Solubility of a solid

A

Dependent on the temperature of the solvent

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18
Q

Saturated solution

A

A solution which contains as much of the solute as possible at a particular temperature of the solvent

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19
Q

Titration use

A

Finds out how much acid or alkali reacts with a certain volume of acid or alkali

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20
Q

Indicators

A

A substance that changes color depending if it is in the pretense of an acid or base

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21
Q

Common indicators in chemistry

A
  • Litmus
  • Thymolphthalein - Blue - colorless
  • Methyl orange
  • Phenolphthalein - colorless - Pink
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22
Q

Process of titration

A
  • Acid is added to alkali through a burette until indicator changes color
  • Alkali is in a conical flask and is constantly swirled
  • Slowly let the acid in drop by drop until a color change
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23
Q

Equipment in a titration

A
  • Beaker xcm^3
  • Filter funnel
  • 3x conical flasks of xcm^3
  • 50cm^3 burette
  • 25cm^3 volumetric pipette
  • Retort stand
  • Clamp
  • xcm^3 of acid and alkali solution
  • Indicator
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24
Q

Steps of a titration

A

1.Add a small volume of alkali to the burette attached to a retort stand by a clamp and rinse out burette with the solution x3
2.add 50cm^3 of alkali to the beaker and then add with a funnel to the top of the burette
3.Remove funnel, and excess solution to the beaker
4.Rinse volumetric pipette with distilled water and x3 with hydrochloric acid
5.Add 25cm^3 of acid to the conical flask
6.Add a few drops of indicator
7.Add the alkali from the burette to the acid in conical flask while swirling until full color change
8.Read the volume from the burette and repeat experiment 2 more times

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25
Q

Concordant volume

A

A volume within +- 0.10cm^3

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26
Q

Use of paper chromatography

A

To separate and identify small quantities of unknown substances with a solution

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27
Q

Process of chromatography

A
  • Unknown substance (solutes) are carried up a sheet of filter paper by a solute
  • Solutes will move at different rates according to their mass and solubility
  • Each substance has a unique retardation factor (Rf) - value of distance a substance travels from the reference line
  • Rf of pure substance is compared to Rf of unknown solute
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28
Q

Chromatogram

A

Filter paper with solute spread across after chromatography procedure is finished

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29
Q

Rf value calculation

A

Rf value = Distance travelled by the solute ÷ Distance travelled by the solvent

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30
Q

Rf value

A

The ratio of distance moved by the solute to the overall distance moved by the solvent - both measured from the reference line

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31
Q

Locating agents

A

Chemical substances that react with colorless solutes in chromatography e.g. amino acids to produce a colored substance that is clearly visible on the chromatogram

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32
Q

Equipment for paper chromatography

A
  • 250 cm^3 beaker
  • Distilled water (solvent)
  • Glass rod
  • 30cm ruler
  • Four capillary tubes
  • 10x15cm rectangle of chromatography paper
  • Pencil - is insoluble
  • Retort stand
  • Clamp
  • Blue, yellow, red and green food coloring - 250cm^3 of each
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33
Q

Steps of paper chromatography

A

1.Place using capillary tube a small volume of each food coloring on the baseline - around 2cm from the bottom edge and spaced out
2.Insert filter paper into a beaker with small volume of water, depth is slightly lower than baseline, top of paper is wrapped around a glass rod
3.Leave the beaker and paper for a suitable period of time to allow the solvent to migrate - keep beaker at constant temperature
4.Remove chromatography paper from the beaker and discard unused solvent

34
Q

Filtration

A
  • Used to separate an insoluble solid from a liquid within a suspension
35
Q

Requirements of filtration

A
  • Use of a filter funnel - insoluble solid material separates from the liquid because it can’t pass through the small hole
  • Conical flask with filter funnel and paper, filtrate/liquid is in the flask and residue is caught in the paper/funnel
36
Q

Crystallization

A
  • Allows pure crystals of a solid to be obtained from a solution as it cools
  • Separates solid and liquid
37
Q

Process of crystallization

A
  • Works best with large difference of solubilities of a solid at high and low temperatures
  • As solution temperature decreases, less space is in the liquid for solid particles, so they push out and grow crystals on the sides
38
Q

Distillation

A

Used to separate one liquid from another in a solution

39
Q

Process of distillation

A
  • Turns one liquid to a gas temporarily
  • Round flask over a bunsen burner with a thermometer at the top, connected to tube where cold water flows
  • Liquid with the lower boiling point will boil, go through the tube and be cooled by the cold water, and drip into the beaker as a liquid
  • Boiling point difference is at least 50˚C
40
Q

Fractional distillation

A

Used to separate two liquids whose boiling points are within 25˚C
- Uses a fractionating column as well made of cool beads to make the liquid with the highest boiling point condense and go back into the flask

41
Q

Fixed points in pure substances

A

Experimentally defined melting and boiling points

42
Q

Types of properties used to determine purity of a substance

A

Physical properties e.g. melting and boiling point

43
Q

Equipment for water purification

A
  • 250cm^3 beaker
  • 250cm^3 conical flask
  • 50cm^3 of 35g/dm^3 of sodium chloride or other substance
  • Bunsen burner
  • Tripod
  • Gauze mat
    Rubber bung with hollow glass tube inserted
  • Plastic tubing
  • Retort stand
  • Clamp
  • Boiling tube
  • Ice
44
Q

Steps of water purification

A

1.Place 50cm^3 of sodium chloride or other substance into the conical flask on top of the gauze mat on the tripod supported by a clamp attached to a retort stand
2.Attach bung connected to plastic tubing to the conical flask and put the end of the tubing into a boiling tube which is placed in a beaker with ice
3.Start eating the conical flask with the bunsen burner
4.As salt water begins to boil collect the distillate in the boiling tube
5.Continue until around 15cm^3 of distillate is collected

45
Q

Gas test for Ammonia (NH3)

A

Damp red litmus paper turn blue

46
Q

Gas test for Carbon dioxide (CO2)

A

Limewater turns milky

47
Q

Gas test for Chlorine (Cl2)

A

Damp litmus paper bleaches white

48
Q

Gas test for Hydrogen (H2)

A

Lighted splint ignites gas with a ‘pop’ sound

49
Q

Gas test for Oxygen (O2)

A

Glowing splint relights

50
Q

Gas test for Sulfur dioxide (SO2)

A

Turns acidified aqueous potassium manganate(VII) from purple to colorless

51
Q

Equipment for Hydrogen gas test

A
  • Test tube
  • 50 cm^3 conical flask
  • 50cm^3 measuring cylinder
  • 2cm magnesium ribbon
  • Dilute solution of dilute hydrochloric acid solution
  • Splint
52
Q

Steps to Hydrogen gas test

A

1.Add 20cm^3 of dilute hydrochloric acid to the flask using a measuring cylinder
2.Add the magnesium strip to the flask
3.Once bubbles form, place the test tube over the mouth of the beaker for a few minutes
4.Quickly remove the test tube, facing down and place a lit split near the mouth of the test tube and invert the tube - audible squeaky pop

53
Q

Flame color of Lithium

A

Red

54
Q

Flame color of sodium

A

Yellow

55
Q

Flame color of potassium

A

Lilac

56
Q

Flame color of copper

A

Blue-green

57
Q

Flame color of barium

A

Light green

58
Q

Flame color of calcium

A

Orange-red

59
Q

Equipment for metal cations flame tests

A
  • Nichrome wire
  • 50cm^3 beaker
  • Bunsen burner
  • Concentrated hydrochloric acid
  • 1mol/dm^3 of each metal
60
Q

Steps of metal cations flame tests

A

1.Using nichrome wire with a loop at one end, clean the loop in some hydrochloric acid
2.Dip the loop in one metal solution and pick up a small volume
3.Place the loop in the hottest pair of the Bunsen flame
4.observe the color
5.Clean the nichrome wire in hydrochloric acid and repeat with the other metals

61
Q

Equation & Product of Aluminum (Al^3+) and aqueous sodium hydroxide

A
  • White precipitate that is soluble in excess and gives a colorless solution
  • Al^3+(aq) + 3OH^-(aq) –> Al(OH)3(s)
62
Q

Equation & Product of Ammonium (NH4^+) and aqueous sodium hydroxide

A
  • Ammonia gas produced on warming - turns red litmus blue
  • NH4^+(aq) + OH^-(aq) –> NH4OH(aq)
  • NH4OH(aq) –> NH3(g) + H2O(l)
63
Q

Equation & Product of Calcium (Ca^2+) and aqueous sodium hydroxide

A
  • White precipitate insoluble in excess
  • Ca^2+(aq) + 2OH^-(aq) –> Ca(OH)2(s)
64
Q

Equation & Product of Chromium(III) (Cr^3+) and aqueous sodium hydroxide

A
  • Green precipitate - soluble in excess
  • Cr^3+(aq) + 3OH^-(aq) –> Cr(OH)3(s)
  • Cr(OH)3(aq) + 3OH^-(aq) –> [Cr(OH)6]^3-(aq)
65
Q

Equation & Product of Copper(II) (Cu^2+) and aqueous sodium hydroxide

A
  • Light blue precipitate - insoluble in excess
  • Cu^2+(aq) + 2OH^-(aq) –> Cu(OH)2(s)
66
Q

Equation & Product of Iron(II) (Fe^2+) and aqueous sodium hydroxide

A
  • Green precipitate - insoluble in excess - precipitate turns brown near surface on standing
  • Fe^2+(aq) + 2OH^-(aq) –> Fe(OH)2(s)
67
Q

Equation & Product of Iron(III) (Fe^3+) and aqueous sodium hydroxide

A
  • Red-brown precipitate - insoluble in excess
  • Fe^3+(aq) + 3OH^-(aq) –> Fe(OH)3(s)
68
Q

Equation & Product of Zinc(II) (Zn^2+) and aqueous sodium hydroxide

A
  • White precipitate - soluble in excess - gives a colorless solution
  • Zn^2+(aq) + 2OH^-(aq) –> 2n(OH2(s)
  • Zn(OH)2(aq) + 4OH^-(aq) –> [Zn(OH)6]^4-(aq)
69
Q

Equation & Product of Aluminum (Al^3+) and aqueous ammonia

A
  • White precipitate - insoluble in excess
  • NH3(aq) + H2O(l) –> NH4OH(aq)
  • Al^3+(aq) + 3OH^-(aq) –> Al(OH)3(s)
70
Q

Equation & Product of Ammonium (NH4^+) and aqueous ammonia

A
  • Doesn’t react
71
Q

Equation & Product of Calcium (Ca^2+) and aqueous ammonia

A
  • No precipitate or very slightly white precipitate
  • Ca^2+(aq) + 6NH3(aq) –> Ca(NH3)6^2+(aq)
72
Q

Equation & Product of Chromium(III) (Cr^3+) and aqueous ammonia

A
  • Green precipitate - insoluble in excess
  • NH3(aq) + H2O(l) –> NH4OH(aq)
  • Cr^3+(aq) + 3OH^-(aq) –> Cr(OH)3(s)
  • Cr^3+(aq) + 6NH3(aq) –> [Cr(NH3)6]^2+(aq)
73
Q

Equation & Product of Copper(II) (Cu^2+) and aqueous ammonia

A
  • Light blue precipitate - soluble in excess - gives a dark blue solution
  • NH3(aq) +H2O(l) –>NH4OH(aq)
  • Cu^2+(aq) + 2OH^-(aq) –> Cu(OH)2(s)
  • Cu^2+(aq) + 4NH3(aq) –> [Cu(NH3)4]^2+(aq)
74
Q

Equation & Product of Iron(II) (Fe^2+) and aqueous ammonia

A
  • Green precipitate - insoluble in excess - precipitate turns brown near surface on standing
  • NH3(aq) + H2O(l) –> NH4OH(aq)
  • Fe^2+(aq) + 2OH^-(aq) –> Fe(OH)2(s)
75
Q

Equation & Product of Iron(III) (Fe^3+) and aqueous ammonia

A
  • Red-brown precipitate - insoluble in excess
  • NH3(aq) + H2O(l) –> NH4OH(aq)
  • Fe^3+(aq) + 3OH^-(aq) –> Fe(OH)3(s)
76
Q

Equation & Product of Zinc(II) (ZN^2+) and aqueous ammonia

A
  • White precipitate - soluble in excess - gives a colorless solution
  • NH3(aq) + H2O(l) –> NH4OH(aq)
  • Zn^2+(aq) + 2OH^-(aq) –> Zn(OH)2(s)
  • Zn^2+(aq) + 4NH3(aq) –> [Zn(NH3)4]^2+(aq)
77
Q

Test & Result for Carbonate (CO3^2-)

A
  • Add dilute acid
  • Effervescence, carbon dioxide produced
78
Q

Test & Result for Chloride (Cl^-)

A
  • Acidify with dilute nitric acid, then add aqueous silver nitrate
  • White precipitate
79
Q

Test & result for Bromide (Br^-)

A
  • Acidify with dilute nitric acid, then add aqueous silver nitrate
  • Cream precipitate
80
Q

Test & result for Iodide (I^-)

A
  • Acidify with dilute nitric acid then add aqueous silver nitrate
  • Yellow precipitate
81
Q

Test & result for Nitrate (NO3^-)

A
  • Add aqueous sodium hydroxide then foil; warm carefully
  • Ammonia produced (turns damp red litmus paper blue
82
Q

Test & result for Sulfate (SO4^2-)

A
  • Acidify, then add aqueous barium nitrate or barium chloride
  • White precipitate
83
Q

Test & result for Sulfite (SO3^2-)

A
  • Add a small volume of acidified aqueous potassium manganate(VII)
  • The acidified aqueous potassium manganate(VII) changes color from purple to colorless

Chemistry IGCSE (12 decks)

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