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chemistry gcse > topic 9 - separate chemistry 2 > Flashcards

topic 9 - separate chemistry 2 Flashcards

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1
Q

why must the test for any ion be unique?

A

you would never be able to know which specific ion it was if more than one ion gave the same result

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2
Q

what are flame tests used to identify?

A

metal ions (cations)

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3
Q

describe the method for flame tests

A
  1. dip wire (platinum/nichrome) in dilute acid
  2. hold in blue flame of bunsen flame
  3. dip loop into solid and place back into blue flame
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4
Q

what colour does lithium (Li+) turn in the flame test?

A

red

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5
Q

what colour does sodium (Na+) turn in the flame test?

A

yellow

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6
Q

what colour does potassium (K+) turn in the flame test?

A

lilac

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7
Q

what colour does calcium (Ca2+) turn in the flame test?

A

orange-red

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8
Q

what colour does copper (Cu2+) turn in the flame test?

A

blue-green

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9
Q

why do we use nichrome alloy and platinum wire?

A

both unreactive (inert) - will not interfere with results

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10
Q

what is a precipitate?

A

an insoluble solid suspended in a liquid

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11
Q

without using flame tests, how can you test for aqueous metal ions?

A

add sodium hydroxide (NaOH)
observe colour change

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12
Q

what is the result of a precipitation reaction with aluminium (Al3+) and sodium hydroxide?

A

white precipitate - adding excess NaOH will dissolve

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13
Q

what is the result of a precipitation reaction with calcium (Ca2+) and sodium hydroxide?

A

white precipitation
adding excess remains

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14
Q

what is the result of a precipitation reaction with copper (Cu2+) and sodium hydroxide?

A

blue precipitate

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15
Q

what is the result of a precipitation reaction with iron II (Fe+) and sodium hydroxide?

A

green precipitate

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16
Q

what is the result of a precipitation reaction with iron III (Fe3+) and sodium hydroxide?

A

brown precipiate

17
Q

what is the result of a precipitation reaction with ammonia (NH4+) and sodium hydroxide?

A

pungent gas produced
forms white smoke of aluminium chloride when hydrogen chloride gas from HCl is held near

18
Q

what is the test for ammonia?

A

warm mixture to produce ammonia gas the put damp red litmus paper near it and it will turn blue

19
Q

what anions do we specifically test for?

A

carbonate, sulfate, and halides

20
Q

how do you test for carbonate (CO32-) ions?

A

add dilute HCl
effervescence could be due to any gas so needs a confirmatory test
gas should be CO2 so can bubble it through like water and see if it turns milky/cloudy

21
Q

how do you test for sulfate (SO42-) ions?

A

add dilute HCl and barium chloride (BaCl2)
positive result = white precipitate formed

22
Q

why do we add dilute HCl when testing for sulfate?

A

to acidify same and remove any carbonate ions

23
Q

how do you test for halide ions?

A

add dilute nitric acid then silver nitrate solution to unknown sample
record colour of ppt. formed

24
Q

what colour ppt does chloride (Cl-) give?

A

white

25
Q

what colour ppt does bromide (Br-) give?

A

cream

26
Q

what colour ppt does iodide (I-) give?

A

yellow

27
Q

what does instrumental methods of analysis mean and examples?

A

methods which use machinery
examples: gas chromatography

28
Q

what are benefits of using instrumental methods of analysis? (3)

A

accurate, sensitive, speed

29
Q

what does a flame photometer measure?

A

light intensity and uses data to determine the concentration of a metal ion in a dilute solution

30
Q

what is a flame photometer graph called?

A

a calibration curve

31
Q

how does a flame photometer work?

A

sample put into flame and light given off is passed through. output is put on a line spectrum and can be analysed

32
Q

why is flame photometry good?

A

can analyse a mixture of ions not just one

chemistry gcse (9 decks)

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