C12 Chemical Analysis Flashcards

1
Q

positive test for hydrogen

A

lighted splint into test tube ‘pops’

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2
Q

positive test for oxygen

A

glowing splint relights

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3
Q

positive test for carbon dioxide

A

turns limewater cloudy

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4
Q

positive test for chlorine

A

turns damp blue litmus paper white

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5
Q

positive test for water

A

cobalt chloride paper changes from blue to pink
or
white anhydrous copper sulfate changes from white to blue

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6
Q

what are flame tests for?

A

to identify the metal ion (cation) by the colour of its flame.

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7
Q

flame colour tests

A

lithium: crimson
sodium: yellow
potassium: lilac
calcium: orange-red
copper: green

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8
Q

describe the steps of a flame test

A
  • dip into hydrochloric acid and high temperature to clean the loop,
  • dip loop into metal compound being tested,
  • hold it in blue flames,
  • use the colour the flames turn to to identify what is the metal compound
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8
Q

describe the steps of a flame test

A
  • dip into hydrochloric acid and high temperature to clean the loop,
  • dip loop into metal compound being tested,
  • hold it in blue flames,
  • use the colour the flames turn to to identify what is the metal compound
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9
Q

ions that form white precipitates with sodium hydroxide solution

A

calcium
and magnesium ions

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10
Q

which metal ions form which-coloured precipitates in sodium hydroxide solution

A

copper II ions form blue precipitate
iron II ions form green precipitate
iron III ions form brown

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11
Q

3 negative ions you can perform chemical tests for

A

sulfates
carbonates
halides (group 7)

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12
Q

how to test for carbonates

A

add dilute acid: if it produces carbon dioxide effervescence (checked with limewater), it is a carbonate

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13
Q

how to test for halides

A
  1. add dilute nitric acid,
  2. add silver nitrate solution,
  3. if precipitate forms, halide ions are present and can be identified by the colour of the precipitate.
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14
Q

precipitate colours for halide ions when added to dilute nitric acid and silver nitrate solution

A

iodide: yellow
bromide: cream
chloride: white

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15
Q

how to test for sulfate ions

A

add dilute hydrochloric acid and barium chloride solution,
white precipitate means sulfate ions are present.

16
Q

what are the advantages and disadvantages of instrumental methods of chemical analysis?

A

advantages
- very accurate and sensitive,
- quicker,
- very small samples can be analysed,

disadvantages
- expensive,
- require special training,
- data can often only be interpreted in comparison to other data *complex and difficult to interpret)

17
Q

which ions does flame emission spectroscopy identify and how?

A

identifies metal ions
by heating a metal substance
and matching the wavelengths of light that it emits to the wavelengths of light emitted by specific metal ions.

18
Q

main advantage of flame emission spectroscopy

A

you can more easily identify multiple metal ions in one substance by matching up the emitted wavelengths to those of many metal ions,
unlike flame tests which - when mixed with many colours - rely on visual estimation