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GCSE Chemistry > C8 Chemical analysis > Flashcards

C8 Chemical analysis Flashcards

1
Q

define pure scientifically

A

consists of only 1 element or compound

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1
Q

define alloy

A

a mixture of 2 or more elements (usually metals)

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2
Q

how many carats gold is 100% gold?

A

24

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3
Q

calculate the percentage of gold if the gild is 9 carat

A

37.5% gold
9/24 x 100

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4
Q

what makes a substance impure?

A

one different atom of molecule

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5
Q

give 3 examples of an alloy

A

steel, bronze, brass

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6
Q

what is steel made out of?

A

iron + carbon

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7
Q

what is steel bronze out of?

A

copper + iron

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8
Q

what is brass made out of?

A

copper + zinc

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9
Q

what is the main property of an impure substance?

A

the melting point is less then that of a pure substance

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10
Q

if a substance is impure, why is the melting point less than that of a pure substance?

A

because it often melts over a range of temperatures of the substances that its made up

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11
Q

how do you know the purity of a substance?

A

the greater the difference between tis known pure melting point, the lower the purity

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12
Q

what is a formulation?

A

a useful mixture with each substance having a precise purpose

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13
Q

how are formulations made?

A

by mixing the components in carefully measured quantities

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14
Q

what are 2 important stages of chromatography?

A

-the stationary phase
-the mobile phase

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15
Q

what are the 2 factors that the travel of a substance in chromatography depend upon?

A

-how soluble the substance is in the mobile
-the affinity to the stationary phase

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16
Q

if there is higher affinity in chromatography how does it affect the travel time?

A

the slower the substance moves in a set time

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17
Q

if there is more solubility in the substance for chromatography how does it affect the travel time?

A

it moves quicker in a set time

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18
Q

in the apparatus setup for chromatography why is there a lid on top?

A

prevents evaporation of solvent

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19
Q

in the apparatus setup for chromatography why is the line a pencil?

A

the pencil doesn’t dissolve in the solvent

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20
Q

in the apparatus setup for chromatography why is water used?

A

it dissolves colours and is absorbed through the paper

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21
Q

describe a method to work out a mixture of colours in the unknown sample is made up of

A

-use a ruler to draw a pencil line 2cm away from the edge of the paper
-put a small spot of known colourings and the unknown on the line equal distance apart
-label each spot in pencil
-pour water into the beaker but make sure the surface isnt toughing the colourings
-keep the paper vertical and ensure it doesn’t touch the beaker walls
-wait for the water to travel 3/4 up the paper
-remove the paper and wait for it to dry
-calculate the Rf values pf all the coloured spots

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22
Q

why do the ink spots in chromatography travel at different distances?

A

they have different solubilities/ affinities

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23
Q

how do you calculate Rf values?

A

distance moved by the substance / distance moved by the solvent

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24
Q

what will a pure compound show after a test of chromatography?

A

only one spot/ Rf value

25
Q

what is the test for hydrogen?

A

-quarter fill a test tube w/ hydrochloric acid and add a small piece of magnesium
-block the end of the test tube to allow the gas to build up
-test the gas with a lighted splint

26
Q

what is the test for oxygen?

A

-quarter fill a test tube with hydrogen peroxide and add a tiny bit of manganese dioxide powder
-block the end of the test tube to allow the gas to build up
-test the gas with a glowing splint

27
Q

what is the test for carbon dioxide?

A

-half fill a test tube with limewater
-quarter fill a boiling tube with hydrochloric acid and add some marble chips
-put a bung with a delivery tube quickly into the boiling tube and the other end into the limewater

28
Q

what is the test for chlorine?

A

-switch on the power supply to the electrolysis of sodium chloride
–wet a piece of litmus paper and hold it over the positive electrode
[if positive then it will blech the damp paper blue]

29
Q

why must the level of solvent in the beaker be below the level of spots in chromatography?

A

the spots will dissolve in the solvent instead of moving up

30
Q

what can flame tests NOT be used for?

A

to identify the metals present in a mixture of metal ions

31
Q

what will the stronger colours do in a flame test?

A

block out the weaker colours

32
Q

what is the line spectrum of a mixture of metal ions?

A

a combination of the line spectra of each individual metal ion present in the sample

33
Q

what are the pros of chemical analysis?

A

-often simple to do
-cheap

34
Q

what are the cons of chemical analysis?

A

-uses up the sample
-not quantitative

35
Q

what are the pros of instrumental analysis?

A

-uses small samples (sensitive)
-fast
-accurate

36
Q

what are the cons of instrumental analysis?

A

-machines can be expensive

37
Q

what is the flame colour for lithium?

A

crimson

38
Q

what is the flame colour for sodium?

A

yellow

39
Q

what is the flame colour for potassium?

A

lilac

40
Q

what is the flame colour for calcium?

A

orange-red

41
Q

what is the flame colour for copper?

A

green

42
Q

what are the Hydroxide precipitates test’s method?

A

Add a few drops of dilute sodium hydroxide solution. Observe and record the colour of any precipitate formed.

43
Q

what precipitate does the positive metal ion aluminium turn (+does it dissolve)?

A

white - yes

44
Q

what precipitate does the positive metal ion calcium turn (+does it dissolve)?

A

white - no

45
Q

what precipitate does the positive metal ion magnesium turn (+does it dissolve)?

A

white - no

46
Q

what precipitate does the positive metal ion copper turn?

A

blue

47
Q

what precipitate does the positive metal ion iron (II) turn?

A

green

48
Q

what precipitate does the positive metal ion iron (III) turn?

A

brown

49
Q

what is the method for the Test for halide ions?

A

Add a few drops of dilute nitric acid, then a few drops of silver nitrate solution. Observe and record the colour of any precipitate formed.

50
Q

what precipitate colour does chloride form?

A

white

51
Q

what precipitate colour does bromide form?

A

cream

52
Q

what precipitate colour does iodide form?

A

pale yellow

53
Q

what is the test for sulphate ions and what do u see if there is a positive result?

A

Add a few drops of dilute hydrochloric acid, then a few drops of barium chloride solution. A white precipitate forms if sulphate ions are present.

54
Q

Sulfate ions can be tested for using a dilute acid and which other solution?

A

barium chloride; Sulfate ions react with barium chloride to form a white precipitate.

55
Q

Some unknown solutions were tested with silver nitrate solution in the presence of dilute nitric acid. The results are shown in the table. Solution 3 did not contain the expected type of ion but another negative ion that reacted with the acid. Name this negative ion.

A

carbonate ion; Carbonate ions react with the nitric acid to form carbon dioxide gas.

56
Q

In flame emission spectroscopy, a sample is put into a flame and the light that is given out is passed through an instrument. What is the name of the instrument?

A

spectroscope

57
Q

Complete the sentence. Carbon dioxide gas is produced when an __________ is added to a carbonate.

A

acid; Acids react with carbonates to form carbon dioxide gas

58
Q

Instrumental methods of identifying ions are particularly useful when the amount of the sample is very __________. What is the missing word in this sentence? large or small

A

small; Instrumental methods are very sensitive, which means that they can detect very small amounts of a sample.

59
Q

Name a carbonate that is soluble in water.

A

sodium; The group 1 carbonates are soluble in water, as is ammonium carbonate.

60
Q
A
61
Q
A

GCSE Chemistry (6 decks)

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