T8 chemical analysis Flashcards

1
Q

what is a pure substance

A

single element or compound, not mixed with any other substance

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2
Q

what is a formulation and how is it made

give examples

A
  • mixture of compounds in measured quantities that has been designed as a useful product
  • formulations include fuels, cleaning agents, alloys, medicines, fertilisers
    e. g. alloys are mixtures of metals, harder than pure metals so have a particular purpose
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3
Q

describe paper chromatography

A
  1. start line is drawn near the bottom of the paper. Mixture is spotted on the line
  2. beaker is filled with small amount of solvent
  3. paper is hung on a rod and placed in a beaker
  4. solvent travels up the paper, separating the components
  5. before solvent level reaches the end, paper is taken out and the finish line is marked, paper is dried
  6. procedure works when different compounds have different affinities for the solvent/paper. Stronger attraction for the paper - travels slowly with the solvent
  7. paper is called the stationary phase - doesn’t move, solvent is the mobile phase
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4
Q

how is Rf calculated

A

distance moved by the spot / distance moved by solvent

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5
Q

describe the tests for hydrogen, oxygen, carbon dioxide and chlorine

A

H - pop with burning split over gas
O - glowing split relights
D - turns limewater (Ca(OH)2) milky
C - bleaches damp litmus paper and makes it white

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6
Q

describe the flame test results

A
lithium compounds - crimson red flame
sodium compounds - yellow flame
potassium compounds - lilac flame
calcium compounds - orange red flame
copper compounds - green flame
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7
Q

describe the test for carbonate anions

A

add dilute acid e.g. HCl

fizzing observed as CO2 released

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8
Q

describe sulfate tests

A

add a solution containing Ba2+ cations

white precipitate pf BaSO4 forms

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9
Q

describe silver nitrate tests

A

add a solution of AgNO3 (acidified with HNO3)
chlorines - white precipitate, silver chloride
bromides - cream precipitate, silver bromide
iodides - yellow precipitate, silver iodide

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10
Q

what are instrumental methods

A

accurate, sensitive and rapid methods which are useful when the amount of sample is very small

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11
Q

describe the flame emission spectroscopy

A

a) instrumental method used for identifying metal ions in solution or measuring their concentration
b) Spectroscope measures the exact wavelength of the light emitted by a metal ion

c) That allows for definite identification - sometimes colours are difficult to
distinguish.

d) Concentrations are found by measuring the intensity of light emitted. The more intense light, the greater the concentration of the metal ion in a solution.

e) From the intensity vs concentration graph, you can read off a relevant
concentration value at a given intensity.

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12
Q

what are cations and anions

A

c - positive ions

a - negative ions

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13
Q

describe the sodium hydroxide test results

A

copper (II) forms a blue precipitate

iron (II) forms a dirty green precipitate

iron (III) forms a brown precipitate

Al3+, Ca2+, Mg2+ forms white precipitate but only Al(OH)3 dissolves in excess NaOH to form a colourless solution

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14
Q

in paper chromatography experiment, a compound A was found to have an Rf value of 0.85 - what does it tell you about the compound

A

has a higher affinity for the solvent than for the paper

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