c4.2 identifying the products of chemical reactions Flashcards

1
Q

how can you detect carbon dioxide

A

you can use limewater (calcium hydroxide)

it turns cloudy white in the presence of carbon dioxide

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2
Q

how can you detect chlorine

A

it dissolves in water to form an acidic solution.

  1. use some water to dampen a blue litmus paper
  2. hold it near to the to the container
  3. if chlorine is present, the paper turns red first and then white
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3
Q

how should you smell in laboratories

A
  1. with the container away from you breathe in enough air to fill your lungs
  2. hold the container a few cm away from you and take a cautious sniff.
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4
Q

detect hydrogen

A

place a lighted splint near the mouth. it should ignite with a squeaky pop.

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5
Q

detect oxygen

A

place a glowing splint near the mouth. it should relight.

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6
Q

what is the flame test colour for lithium

A

red

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7
Q

what is the flame test colour for sodium

A

yellow

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8
Q

what is the flame test colour for potassium

A

lilac

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9
Q

what is the flame test colour for calcium

A

orange-red

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10
Q

what is the flame test colour for copper

A

green-blue

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11
Q

why do elements change colour when heated

A

energy is transferred to their electrons, which makes them move to higher electron shells. When they move back to their normal shell, the energy is transferred to their surroundings by radiation, which we see as light.

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12
Q

what are hydroxide precipitate tests

A

you have to add a few drops of sodium hydroxide solution to a solution containing metal ions.

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13
Q

what is the hydroxide precipitate tests change of colour for iron (II)

A

green

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14
Q

what is the hydroxide precipitate tests change of colour for iron (III)

A

orange-brown

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15
Q

what is the hydroxide precipitate tests change of colour for copper (II)

A

blue

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16
Q

what is the hydroxide precipitate tests change of colour for calcium

A

white

17
Q

what is the hydroxide precipitate tests change of colour for zinc

A

white

18
Q

detect sulfate ions

A

add some drops of dilute hydrochloric acid
then some drops of barium chloride solution
you should get a white precipitate

19
Q

detect carbonate ions

A

add some drops of dilute hydrochloric acid

bubble of gas should be produced if carbonate is there

20
Q

detect halide ions

A
add a few drops of dilute nitric acid
add a few drops of silver nitrate solution. 
chloride: white
bromide: cream
iodide: yellow
21
Q

instrumental methods of analysis advantages

A

sensitivity- they can analyse small amounts of the substance (useful if it is expensive)
accuracy- instruments are very accurate
speed- can carry out analyses very quickly and can be run all the time

22
Q

how to interpret a gas chromatogram

A
  • each peak represents one substance
  • the areas under each peak show the relative amount of that substance in the mixture
  • the retention time is different for each substance
23
Q

how to interpret a mass spectra

A
  • each peak represents a fragement of a molecule
  • the peak on the far right represents a molecular ion
    (the mass to charge ratio of the molecular ion peak is equal to the relative formula mass. )
24
Q

what does a mass spectra show you

A

it measures the masses of atoms and molecules. it is used to analyse the relative amounts of different isotopes of an element, and the structure of molecules.
The mass spectrometer is particularly useful for analysing molecules. The sample molecules are ionised by the machine to form molecular ins. These may break up to form fragments, which the machine can separate and detect.