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Chemistry GCSE 2020 > Foundation: C8 - Chemical Analysis > Flashcards

Foundation: C8 - Chemical Analysis Flashcards

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1
Q

Pures substances are substnace that only contain one type of _____ or ______

A

Element

Compound

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2
Q

Melting and boiling point can be used to determine if a substance is pure. Explain why.

A

If a substance is pure it will melt and boil at specific temperatures.

If it melts or boils above or below this temperature it is not pure (contains impurities).

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3
Q

What is a formulation?

A
  • A mixture with specific proportions/concentrations of some of the components.
  • For example, milk is a mixture but chocolate milkshake is a formulation as it has specific concentrations of some of the components.
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4
Q

Which of the following are formulations?

  1. Petrol
  2. Crude oil
  3. Sea water
  4. 0.5 M hydrochloric acid
  5. Paint
  6. Orange juice (staright from an orange)
  7. Perfume
  8. Steel
A
  • Petrol
  • 0.5 M hydrochloric acid
  • Paint
  • Perfume
  • Steel (it’s an alloy which is a mixture of metals with specific proportions of some of the components)
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5
Q

What is chromatography used for?

A

Seperating different substances (solutes) in a mixture (e.g seperating different chemical in ink or food dye)

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6
Q

Chromatography:

What are the two phases called in chromatography?

What is each pahse made from?

A

Mobile phase: A solvent (e.g water)

Stationary phase: Usually a solid (e.g paper)

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7
Q

Chromatography:

During chromatography some substances move further along the stationary phase (e.g paper) than others, explain why this happens?

A

Substances that are more soluble move further because they spend longer in the mobile phase.

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8
Q

Chromatography:

In the image shown (the right part of it) , how many substances did the ink contain? How can you tell?

A

3 (or more): Because there are 3 spots

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9
Q

Chromatography:

In the image shown, which substance (purple, blue or red) was the most soluble? How can you tell?

A

Blue: It travelled the furthest

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10
Q

Chromatography:

In the image shown, which substance (purple, blue or red) would have the highest Rf value?

A

Blue

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11
Q

Chromatography:

In the image shown, which substance (purple, blue or red) was the least soluble? How can you tell?

A

Red: It travelled the least far

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12
Q

Chromatography:

In the image shown, which substance (purple, blue or red) would have the lowest Rf value?

A

Red

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13
Q

Chromatography:

Chromatography was used to seperate the substances in four different inks. What can you conclude about the substances in the four inks from looking the chromatogram below?

A
  1. Ink 1, 2 and 3 contained 1 substance.
  2. Ink 1, 2 and 3 contained different substances
  3. Ink 4 contained 2 substances.
  4. The substance in ink 1 was the least soluble.
  5. The substance in ink 3 was also in ink 4.
  6. The substance in ink 3 was the most soluble substance.
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14
Q

In the exam they often show you examples of people doing chromatography where they have made mistakes.

What are the common types of mistakes they show? Why are these mistakes a problem?

A
  1. The line is drawn in ink: Ink is soluble
  2. The solvent is above the start line (spots of ink/dye): The ink or dye ill move into the solvent not up the paper.
  3. The wrong solvent (e.g water instead of ethanol) is used: The substances are insoluble in the solvent.
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15
Q

Chromatography:

Rf value =

A

Rf​ value = distance travelled by substance ÷ distance travelled by solvent

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16
Q

Chromatography:

  1. How do you measure distance travelled by a substance in chromotography?
  2. What units do they normally ask you to use in the exam?
A
  1. Measure from the start line to the middle of the spot.
  2. mm
17
Q

Chromatography:

  1. How do you measure distance travelled by the solvent?
  2. What units do they normally ask you to use in the exam?
A
  1. Measure from the start line to the solvent front.
  2. mm
18
Q

Describe the test you would use to identify if a gas is Chlorine.

A
  1. Place a damp piece of litmus paper in the gas.
  2. If chlorine is present the limus paper will turn white
19
Q

Describe the test you would use to identify if a gas is oxygen.

A
  1. Place a glowing splint in the gas
  2. If the gas is oxygen the splint will relight
20
Q

Describe the test you would use to identify if a gas is hydrogen.

A
  1. Place a burning splint in the gas.
  2. If it’s hydrogen you wil hear a squeaky pop.
21
Q

Describe the test you would use to identify if a gas is carbon dioxide?

A
  1. Pass/bubble the gas through limewater.
  2. If the gas is carbon dioxide it will go a milky colour.
22
Q

Triple:

Describe how to test for carbonate (CO32-) ion.

A
  • Add dilute acid.
  • Test if the gas produced is carbon dioxide (which is made if carbonate ions are present).
    • Pass the gas through limewater.
23
Q

Triple:

Describe how to test for sulfate (SO42-) ions?

A
  • Add 2 drops of dilute hydrochloric acid
  • Add 2 drops of barium chloride
  • A white precipitate will form if sulfate ions are present
24
Q

Triple:

Describe how to test for chloride (Cl-), bromide (Br-) and iodide (I-) ions.

A
  • Add 2 drops of dilute nitric acid
  • Add 2 drops of silver nitrate
  • Chloride ions: GIve a white precipitate
  • Bromide ions: Give a cream precipitate
  • Iodide ions: Give a yellow precipitate
25
Q

Triple:

What type of ions give a crimson flame?

A
  • Lithium (Li+)
26
Q

Triple:

What type of ions give a yellow flame?

A
  • Sodium (Na+)
27
Q

Triple:

What type of ions give a lilac flame?

A
  • Potassium (K+)
28
Q

Triple:

What type of ions give an orange-red flame?

A
  • Calcium (Ca2+)
29
Q

Triple:

What type of ions give an green flame?

A
  • Copper (Cu2+)
30
Q

Triple:

Describe how to test for metal ions using the flame test.

A
  1. Use a clean nichrome wire loop
  2. Dip the loop in the sample (salt or solution)
  3. Record the colour of the flame
31
Q

Triple:

Describe how to test for metal ions using sodium hydroxide.

A
  1. Add a few drops of sodium hydroxide to a solution containing the unidentified ions.
  2. Different metal ions will give different colour precipitates.
32
Q

Triple:

  1. When sodium hydroxide is added to a solution what colour precipitate is given if calcium (Ca2+), magnesium (Mg2+) or aluminium (Al3+) ions are present?
  2. How can you distiguish the aluminium ions from the calcium and magnesium ions?
A
  1. White
  2. If you keep adding sodium hydroxide the white precipitate eventually redissolves with aluminium ions.
33
Q

Triple:

When sodium hydroxide is added to a solution what colour precipitate is given if copper (II) (Cu2+) ions are present?

A

Blue

34
Q

Triple:

When sodium hydroxide is added to a solution what colour precipitate is given if Iron (II) (Fe2+) ions are present?

A

Green

35
Q

Triple:

When sodium hydroxide is added to a solution what colour precipitate is given if iron (III) (Fe3+) ions are present?

A

Brown

36
Q

Triple:

Why do ions emit light when heated?

A
  1. As ion is heated electrons gain energy
  2. They become exited/move to a higher energy level
  3. When electrons move back to their original energy level, energy is released as light.
37
Q

Triple:

Why do different ions emit different wavelengths of light when heated?

A

They have different charges (e.g Li1+ and Be2+)

or

Different electron arrangements (e.g Ca2+ and Mg2+)

Chemistry GCSE 2020 (20 decks)

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