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C8 Chemical Analysis

Last updated about 1 month ago
32 questions
4.8.1.1 Pure substances
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A pure substance has to be an element

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A mixture is always an impure substance.

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Impure substances have higher boiling points

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Salt is put on ice to increase the melting point.

2

Identify 2 differences between pure and impure substances

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What happens to the melting point of water when impurities are added?

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Many people would say that spring water is pure. Is this a pure substance? Explain your answer.

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A student compared a sample of isooctane with some petrol. The student found that the octane boiled at 99°C while the petrol boiled between 45 and 95°C. Which of these is a pure substance? Explain your answer.

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Explain why salt is placed on roads in winter months?

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4.8.1.2 Formulations
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A green ink contains 85% yellow dye and 15% blue dye.
Determine the simplest whole number ratio of yellow dye : blue dye in the green ink.

Yellow dye : Blue dye =

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A fertiliser contains 0.225 g of iron per 3.0 g of fertiliser.

Which calculation gives the percentage of iron in the fertiliser?

Tick one

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Formulations have specific amounts of each chemical

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Diesel is a formulation. What is a formulation?

4.8.1.3 Chromatography
4.8.2 Identification of common gases
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Use the ruler tool on this chromatogram - you will need this to answer the next questions.

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How many substances are in dye A?

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How many substances are in Dye B?

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Calculate the Rf value for substance P

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Calculate the Rf value for substance Z

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Calculate the Rf value for substance Y

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Calculate the Rf value for substance X

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Explain how the chromatogram shows that A is a pure substance and B is a mixture.

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Why is the start line drawn in pencil rather than pen?

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In chromatography, ink is the solvent.

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In chromatography, the dyes are soluble in water.

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Chromatography allows us to separate different elements in a compound.

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Simple distillation allows us to separate liquids with different boiling points.

2

What colours are in substance P?

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Put the order of Chromatography in order

  1. Lay the paper flat and leave it to dry
  2. Draw a line with a pencil and ruler to one end of the strip of filter paper
  3. Suspend the filter paper in a beaker so it isn't touching the sides or the bottom
  4. Cover the beaker and wait a few minutes
  5. When the solvent has almost reached the top of the filter paper, remove it from the beaker
  6. Place a spot of ink on the pencil line
  7. Use a ruler to measure the distance the ink spot has travelled (Rf values)
  8. Carefully add the solvent to a level just below the ink spot, taking care not to splash the paper
1

Match the gas test to its positive result

Draggable itemCorresponding Item
Place a glowing splint in a test tube of the gas
Limewater turns milky (cloudy)
Put Damp litmus paper into the gas
Litmus paper is bleached and turns white
Shakes or bubble the gas through limewater
A squeaky pop sound is produced
Hold a burning splint at the open end of a test tube of the gas
The splint relights.
…
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This question is about gas tests - sort into Tests and Results

  • Hold a burning splint at the open end of a test tube of the gas
  • The splint relights
  • A squeaky pop sound is produced
  • Limewater turns milky (cloudy)
  • Place a glowing splint in a test tube of the gas
  • Shakes or bubble the gas through limewater
  • Put Damp litmus paper into the gas
  • Litmus paper is bleached and turns white
  • Test
  • Result
…
4.8.3.1 Flame Tests
4.8.3.2 Metal Hydroxides
4.8.3.3/4/5 Antions (Carbonate, Halide, Sulfate)
4.8.3.6 Instrumental Methods
4.8.3.7 Flame Emission Spectroscopy