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Chemistry: Module 3 > Qualitative Analysis > Flashcards

Qualitative Analysis Flashcards

test for ions

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1
Q

what is the formula for carbonate ions?

A

CO3(2-)

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2
Q

what is formed when carbonates react with acids?

A

carbon dioxide gas

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3
Q

how do you test for the presence of carbonate ions?

A
  • in a test tube, add dilute nitric acid to an unknown solution
  • if effervescence is produced/seen, test with limewater
  • if limewater turns cloudy, CO2 is confirmed and thus carbonate ions present
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4
Q

what is the formula for sulfate ions?

A

SO4(2-)

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5
Q

how do you test for the presence of sulfate ions?

A
  • add barium chloride (BaCl2) to an unknown solution
  • if white precipitate (barium sulfate) is formed, sulfate ions are present
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6
Q

what is the formula for halide ions?

A

Cl-, Br-, I-

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7
Q

how do you test for the presence of halide ions?

A
  • add silver nitrate (AgNO3) to the unknown solution
  • coloured precipitate forms depending on the halide ion present
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8
Q

what colour precipitate are chloride ions?

A

white

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9
Q

what colour precipitate are bromide ions?

A

cream

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10
Q

what colour precipitate are iodide ions?

A

yellow

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11
Q

why do flouride ions not have a test?

A

they are soluble so dont give a precipitate

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12
Q

how can you differentiate between the halide ions precipitates?

A
  • add dilute aqueous ammonia to AgCl = dissolve precipitate
  • add concentrated aqueous ammonia to AgBr = dissolve precipitate
  • add concentrated aqueous ammonia to AgI = doesn’t dissolve
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13
Q

what is the formula for ammonium ions?

A

NH4(+)

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14
Q

how do you test for the presence of ammonium ions?

A
  • add sodium hydroxide (NaOH) to the unknown solution
  • ammonia gas is produced but cannot be seen as it is very soluble in water
  • the mixture is warmed and ammonia gas is released
  • to test if the gas is ammonia gas use damp red litmus paper which will turn blue
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15
Q

what are the anions being tested?

A

sulfate, carbonate and halide ions

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16
Q

what are the cations being tested?

A

ammonium ions

17
Q

what order do we test the ions?

A

carbonate, sulfate and halide (cringing so hard)

18
Q

what is the ionic equation for ammonium ions?

A

NH4+(aq) +OH-(aq) –> NH3(aq)+ H20(l)

19
Q

why does the sequence of test for ions matter?

A

BaCO3 and Ag2SO4 are insoluble

Chemistry: Module 3 (12 decks)

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