measurement Flashcards
(84 cards)
1
Q
Gas syringe purpose
A
collect and measure the volume of gas up to 100cm3
2
Q
rough calibration
A
known volume
3
Q
SI unit for time
A
second (same as record timing)
4
Q
si unit for temp
A
kelvin (K)
5
Q
record temp to the nearest
A
0.5 degree celsius
6
Q
conversion of temp to kelvin
A
273 + degree celcius
7
Q
si unit for mass
A
kilogram
8
Q
record mass to the nearest
A
0.1g without plastic cover, 0.01 with
9
Q
SI unit for volume of gas
A
m3
10
Q
record volume of gas depend on
A
instrument
11
Q
volume is commonly measured in
A
cubic centimetre and cubic decimeter
12
Q
1dm3 is
A
1000cm3
13
Q
the methods of gas collection depends on
A
solubility of gas in water and density of gas to air
14
Q
downward delivery is for gases that are
A
denser than air
15
Q
gases that are denser than air are
A
carbon dioxide CO2 and chlorine gas Cl2
16
Q
upward delivery of gas is for gases that are
A
less denser than air
17
Q
less dense than air are gases like
A
ammonia NH3 and hydrogen H2
18
Q
displacement of water is for gases that are
A
insoluble or slightly soluble in water
19
Q
gases that are insoluble or slightly soluble are gases like
A
hydrogen, nitrogen N2, oxygen O2 and carbon dioxide
20
Q
why can you not use concentrated sulfuric acid to dry ammonia
A
ammonia is an alkaline gas and will react with the acid
21
Q
why can you not use quicklime (calcium oxide) to dry sulfur dioxide and hydrogen chloride
A
since quicklime will react with acidic gases
22
Q
fused calcium is a calcium chloride that has been
A
heated to remove water
23
Q
fused calcium can dry most gases but cant dry ammonia because
A
it reacts to form a complex
24
Q
what is purification
A
its a process to separate pure substances from mixures or impurities
25
filtration is used to separate
insoluble solids from a liquid-solid mixture
26
when to use evaporation to dryness
to obtain a soluble solid from its solvent until the all solvent is boiled off. For the solid that does not decompose during strong heating
27
1st step for evaporation to dryness
heat the solution until all the water has evaporated
28
2nd step for evaporation to dryness
ensure the soluble solid must be stable to heat so that it does not decompose on heating and must not contain water of crystallisation. Solid obtained is not always pure, any soluble impurities will be left with the solid
29
water of crystallisation refers to
water molecules that make up the structure of a salt crystal
30
when to use crystallisation
to obtain a soluble PURE solid from its concentrated solution is the solid decomposes on strong heating
31
crystallisation occurs when
a saturated solution (a solution in which no more solid can be dissolved) is cool
32
1st step to obtain pure crystals
dissolve impure solid in water until no more can be dissolved
33
crystallisation is based on the principle that the
solubility of compounds increases with temp
34
2nd step to obtain pure crystals
filter the solution to remove extra undissolved solid and insoluble impurity
35
3rd step to obtain pure crystals
heat the solution till saturation
36
4th step to obtain pure crystals
leave the hot saturated solution to cool. crystals will start to form in the solution
37
5th step to obtain pure crystals
the cooled solution is then filtered to obtain the pure crystals. The crystals are dried by pressing them gently between sheets of filter paper
38
a crystal is pure because
only the particles of the compound arrange together to form a highly ordered structure. impurities are left behind in the solution
39
how to check for saturation
dip a clean glass rod into the solution and remove it. if small crystals form on the rod when the solution cools, the solution is saturated. The slower the rate of cooling, the larger the crystals.
40
when is sublimation used
to separate a mixture of solids, in which one of the solids will become a gas when heated
41
1st step to sublimation
heat the mixture. the vapour of the sublimed solid is cooled to yield the solid.
42
solids that sublime on heating include
ammonium chloride, iodine and carbon dioxide
43
when to use simple distillation
when separating a pure solvent from a solution
44
1st step to distillation
heat the solution in a distillation flask connected to a condenser
45
2nd step to distillation
the liquid boils and its vapour enters the cold condenser where condensation takes place
46
3rd step to distillation
the vapour is converted back to its pure liquid form and collected as the distillate
47
when to use fractional distillation
to obtain a pure liquid from a solution of two or more miscible liquids with different boiling points
48
miscible liquids are those that are
completely soluble in one another when mixed
49
the liquids in fractional distillation are separated according to their
boiling points
50
for fractional distillation, the liquid with the lowest boiling point will be
distilled first
51
whats the principle of fractional distillation
the liquid with the lowest boiling point distills off first
52
when to use a separating funnel
when separating immiscible liquids
53
immiscible liquids are liquids that
do not mix with one another
54
a separating funnel has
a stopper covering the top and a tap at the bottom
55
a mixture of two immiscible liquids will form
two separate layers
56
the less dense liquid will be on top while the denser liquid will
sink to the bottom of the funnel
57
paper chromatography is used to
separate and identify of both coloured and colourless mixtures such as drugs and dyes
58
the solvent comes into contact with the
bottom of the chromatography paper and moves up by capillary action
59
(chromatography) different substances in the mixture become separated as they
travel at different rates due to the varying solubilities in the solvent
60
some inks are water soluble and some are not. To separate non soluble water components, use
ethanol
61
separated substances are identified by
comparing their positions on paper with that of known substances, calculating the retention factor
62
retention factor is obtained by
dividing the distance travelled by the solute up the paper by the distance travelled by the solvent
63
for substances that share the same retention factor value, choreography can be performed with
a different solvent to distinguish them
64
for separating colourless compounds,use
locating agents are used to show the position of these compounds in the chromatogram
65
locating agents are substances that
react to form coloured products with the colourless compounds
66
state the 3 drying agents
concentrated sulfuric acid, quicklime (calcium oxide), calcium chloride
67
pure substances are made of
one single element or compound
68
state the process of filtration
1. pour the mixture into a filter funnel that is lined with filter paper. 2. collect the filtrate that passes through the filter paper in a beaker. 3. wash the residue with some distilled water to remove impurities. 4. dry the residue between pieces of filter paper
69
during crystallisation, water is
removed when heated
70
during crystallisation, heating is stopped when
a hot saturated solution is formed
71
crystallisation procedure
1. using a glass rod, stir and dissolve the impurities in water. 2. pour the mixture into filter funnel lined with filter paper, filter to remove any insoluble impurities, and collect filtrate in a beaker. 3. Heat solution till saturated. 4. when solution is saturated, leave it it to cool at room temp, crystals will start to form in the solution. 5. filter to collect the crystals, wash the crystals with cold distilled water to remove impurities. 6. Dry the crystals with filter paper
72
Using a suitable solvent when a mixture of two solids in which
only one is soluble in the solvent
73
a substance that sublimes has the same
melting and boiling point
74
examples of solids that sublimes
iodine, ammonium chloride, carbon dioxide, and naphthalene
75
during sublimation, the surface must be
lower temp than the mp and bp of the solid
76
describe an advantage of chromatography over other physical methods of separation
chromatography only requires filter paper and a solvent, it is not as costly as other physical methods
77
explain why test tubes are enclosed with a cork during chromatography
to make the atmosphere in the container become saturated with solvent vapour, so that it can prevent the solvent from evaporating as it rises up the paper
78
Mixture in chromatography is when there are ____ spots
more than 1
79
caveats for simple distillation (thermometer and condenser)
Thermometer should be placed near the outlet of the flask, ensures the thermometer measures the boiling point of the vapour instead of the heat from the flame. Water should be flowing against the flow of vapour. This ensures the presence of a permenant cold surface in which all vapour condenses into liquid effectively before leaving the condenser.
80
Volatile liquid is
near room temp
81
important role of fractionating column
provides large surface area for evaporation and condensation of vapour of different liquids so that the separation of liquids can be more efficient.
82
eg for physical changes
liquid to gas, solid to liquid
83
principle of chromatography
different dyes have different solubility in the solvent (water) so they travel from the center of the paper at different speeds. The more soluble the dye, the further it will travel from it
84
ascending chromatography is faster because
it moves in the same direction as gravity
