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Chemistry > Chapter 8 - Chemical Analysis > Flashcards

Chapter 8 - Chemical Analysis Flashcards

1
Q

What do we use flame tests for?

A

To determine what metal ions are in a metal compound

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2
Q

What is the flame test method?

A
  1. Put Nichrome wire in the acid
  2. Put looped end into chemical you are testing
  3. Put loop into the hottest part of a roaring blue flame
  4. Observe colour change
  5. Clean wire by dipping in acid and checking no colour is produced in the flame before repeating with other chemicals
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3
Q

Lithium (Li+) Flame Colour

A

Crimson

-crimson lipstick - lipstick for lithium

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4
Q

Sodium (Na+) Flame Colour

A

Yellow

-sodium = so damn loud > YELLow

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5
Q

Potassium (K+) Flame Colour

A

Lilac

-lilac flowers in pots - pots = potassium

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6
Q

Calcium (Ca2+) Flame Colour

A

Orange-red

-CALum Scott is so hot - hot connotes red

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7
Q

Copper (Cu2+) Flame Colour

A

Green

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8
Q

Why do the flames have colours?

A

When heated the electrons jump to another energy level (shell) as they have more energy. As they fall back to their original energy level, the energy is emitted as a light wavelength.

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9
Q

What do we use a flame emission spectroscope for?

A

To use to produce a line emission spectra which shows what colour is given off at specific energy levels

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10
Q

What are the advantages of using instrumental methods over a flame test?

A
  • more accurate
  • higher sensitivity
  • faster
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11
Q

What is the graph that is used to find the concentration of ions called?

A

Calibration curve

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12
Q

Practical: Adding NaOH - what is the method?

A
  1. Dissolve solid sample in distilled water
  2. Put solution into test tube (about 2cm depth)
  3. Add NaOH drop by drop
  4. Mix after each drop and check for any precipitate
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13
Q

What happens when you add NaOH to aqueous Cu2+?

A

Light blue precipitate formed

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14
Q

What happens when you add NaOH to aqueous Fe2+?

A

Green precipitate - slowly turns brown

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15
Q

What happens when you add NaOH to aqueous Fe3+?

A

Reddish-brown precipitate formed

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16
Q

If no precipitate is formed when NaOH is added, what do we do to test for ammonia ions?

A

Warm the solution
If ammonia present:
-Gives off NH3 smell
-Turns litmus paper blue

17
Q

What happens when you add NaOH to aqueous non-transition metals e.g. Al3+ Ca2+ and Mg2+?

A

White precipitate formed

18
Q

How can we differentiate between Al3+ Ca2+ and Mg2+?

A

Add more NaOH
If the precipitate dissolves then it is Al3+
If it does not dissolve either Ca2+ or Mg2+ are present

19
Q

What is the gas test for hydrogen?

A

Put a lit splint in a test tube and if hydrogen is present there will be a squeaky pop

20
Q

What is the gas test for oxygen?

A

If a glowing splint relights oxygen is present

21
Q

What is the gas test for chlorine?

A

Use damp litmus paper. If chlorine is present it will bleach the litmus and turn it from blue to white

22
Q

What is the gas test for carbon dioxide?

A

Bubble through limewater and if carbon dioxide is present it well turn from colourless to cloudy/milky

23
Q

Define pure in chemical terms

A

Only one type of element / compound with no other substance

24
Q

What is a formulation?

A

A mixture that has been designed as a useful product e.g. fuels, medicines, paints and cleaning agents

25
Q

What can be used to identify if something is pure or impure?

A

Melting or boiling point

26
Q

What is the equation for finding the retention factor during chromatography?

A

Rf = distance of spot from baseline/distance of solvent from baseline
Rf < or = 1

27
Q

What is chromatography used for?

A

To separate mixtures of colours

28
Q

What is the method for testing for carbonate ions?

A
  1. Dissolve carbonate in water
  2. Add dilute HCl (it will fizz)
  3. Use bung to capture gas and transport gas through delivery tube to be bubbled through limewater
  4. Limewater turns milky/cloudy if CO2 is present.
29
Q

What is the method for testing for halide ions?

A
  1. Dissolve halide in water
  2. Add dilute nitric acid
  3. Add silver nitrate drop by drop
  4. If precipitate forms observe the colour
30
Q

What colour precipitate does chlorine form?

A

White

31
Q

What colour precipitate does bromine form?

A

Cream

32
Q

What colour precipitate does iodine form?

A

Yellow

33
Q

What is the method for testing for sulfate ions?

A
  1. Dissolve sulfate in water
  2. Add dilute HCl (won’t fizz)
  3. Add barium chloride [TOXIC] drop by drop
  4. If dense white precipitate forms (barium sulfate) sulfate ions are present

Chemistry (11 decks)

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