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Chemistry > Chemical Tests > Flashcards

Chemical Tests Flashcards

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1
Q

test for chlorine

A

chlorine bleaches damp blue litmus paper, turning it white. (it may turn red for a moment first though - thats because a solution of chlorine is acidic)

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2
Q

how can you show whether a sample of water is pure?

A
  • pure = one substance, which means SET physical properties like boiling and freezing point
  • water boils at 100 and freezes at 0. if it boils over a range of temps it is impure
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3
Q

how can you test for the presence of water?

A
  • when copper(II) sulphate is bound to water it forms lovely blue crystals
  • if you heat the blue hydrated copper(II) sulphate crystals it drives the water off
  • this leaves a white anhydrous copper(II) sulphate copper sulphate powder, which doesn’t have any water bound to it.
  • if you add a couple of drops of water to the white powder you get the blue crystals back again
  • if you want to test for water, add water to anhydrous copper(II) sulphate and see if it turns blue.
  • this will tell you if water is present but not if its pure
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4
Q

how can you test for halides?

A
  • halides = Cl-, Br-, I-
  • add dilute nitric acid (HNO3) followed by silver nitrate solution.
  • a CHLORIDE ion gives a WHITE precipitate of silver chloride
  • a BROMIDE ion gives a CREAM precipitate of silver bromide
  • an IODIDE ion gives a YELLOW precipitate of silver iodide
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5
Q

how can you test for sulphates?

A
  • sulphate ions produce a white precipitate
  • add dilute HCl, followed by barium chloride solution BaCl2
  • a white precipitate of barium sulphate means the original compound was a sulphate
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6
Q

how can you test for carbonates?

A
  • add dilute hydrochloric acid to your test sample
  • if carbonates (CO32-) are present then carbon dioxide will be released
  • you can test for carbon dioxide using limewater
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7
Q

how can you test for the cation Fe3+?

A
  • add a few drops of sodium hydroxide solution to a solution of your mystery compound in a test tube.
  • if you get a coloured insoluble hydroxide you can then tell which metal was in the compound
  • iron (III) should be REDDISH BROWN
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8
Q

how can you test for the cation Fe2+?

A
  • add a few drops of sodium hydroxide solution to a solution of your mystery compound in a test tube.
  • if you get a coloured insoluble hydroxide you can then tell which metal was in the compound
  • iron (II) should be SLUDGY GREEN
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9
Q

how can you test for the cation Cu2+?

A
  • add a few drops of sodium hydroxide solution to a solution of your mystery compound in a test tube.
  • if you get a coloured insoluble hydroxide you can then tell which metal was in the compound
  • copper (II) should be BLUE precipitate
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10
Q

how can you test for the cation NH4+?

A
  • first test for ammonia gas using damp red litmus paper. if theres ammonia present it will turn blue
  • then test whether a substance contains ammonium ions (NH4+).
  • add some sodium hydroxide to a solution of the mystery substance in a test tube. if theres ammonia gas given off (which smells like cat wee) this means there are ammonium ions in the substance
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11
Q

what colour does the cation COPPER burn with?

A

BLUE-GREEN

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12
Q

what colour does the cation CALCIUM burn with?

A

ORANGE-RED

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13
Q

what colour does the cation POTASSIUM burn with?

A

LILAC

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14
Q

what colour does the cation SODIUM burn with?

A

YELLOW

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15
Q

what colour does the cation LITHIUM burn with?

A

RED

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16
Q

how do you carry out a flame test?

A
  • clean a platinum wire loop by dipping it in dilute HCl then holding it in a flame. once you hold the loop in the flame and it burns without any colour
  • you can dip it in the sample you want to test and put it in the clear blue part of the bunsen flame (hottest part)
  • then say oooooh and aaahhhhh :)
17
Q

test for ammonia

A

ammonia turns damp red litmus paper blue. (it also has a very strong smell)

18
Q

test for hydrogen

A

hydrogen makes a “squeaky pop” noise with a lighted splint. (the noise comes from the hydrogen burning with the oxygen in the air to form H2O)

19
Q

test for carbon dioxide

A

carbon dioxide turns limewater cloudy - just bubble the gas through a test tube of limewater.

20
Q

test for oxygen

A

oxygen relights a glowing splint

Chemistry (24 decks)

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