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GCSE Chemistry > Chemical Analysis > Flashcards

Chemical Analysis Flashcards

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1
Q

Chlorine test?

A

Hold damp litmus paper at the neck of a test tube, if chlorine is present, the damp litmus paper will be bleached by the chlorine

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2
Q

Oxygen test?

A

Hold a glowing splint at the neck of a test tube, if oxygen is present, it will relight

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3
Q

Hydrogen test?

A

Hold a lit splint at the neck of a test tube. If hydrogen is present, a squeaky pop sound is observed

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4
Q

Carbon dioxide test?

A

Bubble the gas being tested through lime water, if the gas is/contains CO2, the lime water will turn cloudy

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5
Q

How to carry out paper chromatography?

A
  1. Draw a line near the bottom of a sheet of paper
    - use pencil as it is insoluble
  2. Add a spot of ink the line using a capillary tube, and place the sheet in a beaker of solvent (water, ethanol…)
    - make sure the ink isn’t touching the solvent so that it doesn’t dissolve in it
  3. Optional - place a lid on the beaker to stop the solvent evaporating
  4. The solvent seeps up the paper, carrying the ink (solute) with it
  5. Each different dye in the ink will move up the paper at a different rate so the dyes will separate out. Each dye will form a spot in a different place
  6. When the solvent has nearly reached the top of the paper, remove it from the beaker and leave it to dry
  7. The end result is a pattern of spots called a chromatogram
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6
Q

What determines how far up the dyes travel up the paper?

A

The relative solubility of components making up a mixture determines how far they travel up the paper, The more soluble, the further it is carried

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7
Q

What is the mobile phase?

A

The mobile phase is the solvent that moves through the paper, carrying different substances with it

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8
Q

What is the stationary phase?

A

The stationary phase, is what the mobile phase moves through

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9
Q

What does it mean for a substance to be pure? examples

A

A substance made up of just 1 element or compound

  1. oxygen
  2. carbon dioxide
  3. distilled water
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10
Q

What is a mixture? examples

A

A mixture is a material made up of two or more different substances which are not chemically combined.

  1. air
  2. crude oil
  3. sea water
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11
Q

What is chromatography used for?

A

Chromatography is used to separate mixtures of substances into their components

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12
Q

What is simple distillation used for?

A

Simple distillation is used to separate a solvent from a solution

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13
Q

How does simple distillation work?

A
  1. The solution is heated. The part of the solution that has the lowest boiling point evaporates first
  2. The vapor is then cooled, condenses and collected
  3. The rest of the solution is left behind in the flask
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14
Q

What is the problem with simple distillation?

A

You can only use it to separate things with very different boiling points if the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again.

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15
Q

What is fractional distillation used for?

A

To separate a mixture of liquids

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16
Q

How does fractional distillation work?

A
  1. You put the mixture in a flask and place a fractionating column on top. Then you heat it
  2. The different liquids will have different boiling points and therefore evaporate at different temps
  3. The liquids with the lowest boiling point evaporates first - when the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column
  4. If liquids with higher boiling points start evaporating, because the flask is cooler up top, they will condense and run back down
  5. When the first liquid has been cooled, condensed and collected, the temperature is rising till the next one reaches the top to be cooled, condescended and collected
17
Q

What is filtration used for?

A

To separate insoluble solids from liquids

18
Q

How does filtration work?

A

Filter paper is folded into a cone shape and placed in a funnel. The mixture is then poured through and the liquid pases through however the insoluble solid is to large to pass through the filter paper and is therefore left behind as residue

19
Q

What is evaporation used for?

A

To separate a soluble solid from a solution

20
Q

How does evaporation work?

A
  1. The solution is poured into an evaporation disk
  2. The solution is slowly heated, this causes the solvent to evaporate and the solution to get more concentrated, eventually crystals will start to form
  3. The evaporating dish is heated till all that is left are dry crystals
21
Q

What is crystallisation used for?

A

To separate a soluble solid from a solution

22
Q

How does crystallisation work?

A
  1. The solution is poured into an evaporation disk
  2. The solution is slowly heated, this causes the solvent to evaporate and the solution to get more concentrated
  3. Once the solvent has evaporated or when crystals start to form - the point of crystallisation - remove the dish from the heat and leave to cool
  4. Salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
  5. finally leave the crystals to dry in a warm place - or a drying oven/ desiccator
23
Q

What is a formulation?

A

Formulations are useful mixtures with exact amounts of components - they have a precise purpose and are made by following a formula
each component in a formulation has a measured Quantity and contributes to the properties of the formulation so that it meets its required function

24
Q

RF value =

A

distance traveled by substance / distance traveled by solvent

25
Q

What tells you how pure a substance is?

A

The boiling point. A chemically pure substance will boil at a specific temperature. Impurities in a substance will lower the boiling point and increase the boiling range of the substance

26
Q

Examples of formulations

A
  1. paints
  2. drugs
  3. alloys
  4. fuels
  5. fertilisers
27
Q

Mistakes with chromatography

A
  1. Line in pencil
  2. Pencil line must be above surface of water
  3. Paper sides must not touch beaker
  4. Lid can be used
28
Q

How does chromatography work?

A

It works because some of the substances dissolve in the solvent used better than others, so they travel further up the paper because the solvent carries them up further.

29
Q

Relative atomic mass?

A

total mass of all atoms/total number of atoms
total mass = mass number * abundancy
- for all isotopes
total number of atoms = sum of all abundances

GCSE Chemistry (5 decks)

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