purity, formulations, chromatography, instrumental analysis Flashcards

1
Q

chemical definition of a pure substance

A

a single element or compound not mixed with any other substance

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2
Q

everyday definition of a pure substance

A

a substance that has had nothing added to it and is in its natural state

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3
Q

how to distinguish between pure and impure substances

A

pure substances boil and melt and specific temperatures, so any variation in the melting and boiling point means substance is impure.

impure = melt and boil over a range of temperatures

impure decrease melting points and increase boiling point

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4
Q

what is a formulation (3 points)

A

a mixture designed as a useful product where each chemical involved has a particular purpose and is added in measured quantities (ensures right properties)

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5
Q

7 examples of formulations

A
  1. fuels
  2. cleaning agents
  3. paints
  4. medicines
  5. alloys
  6. fertilisers
  7. foods
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6
Q

chromatography (for full method refer to topic 1): used for? (2)

A

separate mixtures and identify substances

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7
Q

Rf value: what is it and how to calculate

A

distance moved by the compound (the centre of the spot to the original line) : distance moved by solvent

distance moved by substance / distance moved by solvent

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8
Q

how to use chromatography to identify same compounds and a pure compounds

A

compound have different Rf values in different solvents

a pure compound will produce 1 single spot.

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9
Q

how does chromatography separate mixtures

A

different compounds in the mixture has different solubility therefore they rise to different points- most soluble furthest-. create series of spots on chromatogram. attraction to the paper

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10
Q

what are instrumental methods of analysis

A

ways to detect elements and compounds using machinery

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11
Q

3 advantages of instrumental analysis

A
  1. sensitive- detect tiny amounts of substance
  2. fast
  3. accurate
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12
Q

3 types of instrumental analysis

A
  1. flame emission spectroscopy
  2. mass spectroscopy
  3. infrared spectroscopy
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13
Q

process of flame emission spectroscopy + how is concentration detected

A
  1. sample placed in a flame
  2. heat causes electrons to excite and move to higher energy levels
  3. when they drop back into original energy levels, they release energy as light
  4. light passes through a spectroscope which detects the wavelengths of light emitted

concentration = intensity of light

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14
Q

how to use flame emission spectroscopy to identify ions in a compound

A

no 2 ions have the same spectroscope as their electron arrangements different

tell ions in a compound by seeing which ions’ spectroscope matches up, concentration of the ion = intensity

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