Chemical Analysis (seneca) Flashcards
1
Q
A chemically pure substance is a
A
single element or compound that only contains only one substance
2
Q
Chemical purity is worked out by looking at
A
melting and boiling points of a sample
3
Q
what are some examples of pure substances?
A
- water
- copper sulfate
- oxygen gas
- sodium chloride
4
Q
Impurities 1. the melting point of a sample and 2. the range of temperatures at which the sample will melt.
A
- lower
- widen
5
Q
Impurities 1. the boiling point and 2. the range of temperatures at which the sample will boil.
A
- increase
- widen
6
Q
Formulations are …
A
mixtures of chemicals that have been designed to create useful products.
7
Q
In a formulation, each component helps to decide what the mixture’s …
A
overall properties are.
8
Q
To make sure that a formulation does what it is supposed to, each chemical component must be present in a …
A
precisely measured quantity.
9
Q
Formulations are everywhere around us in day-to-day life. Examples include:
A
- Fuels
- Cleaning agents
- Metal alloys
- Fertilisers
- Medicines
10
Q
The closer the experimentally recorded melting or boiling points are to those found in the data book, the greater the —– of a sample.
A
purity
11
Q
Chromatography is a process that separates …
A
a mixture into its different components.
12
Q
what are the 2 phases in chromatography?
A
- Substances are picked up and carried by a mobile phase (liquid or gas).
- The mobile phase then moves through a stationary phase (solid or viscous liquid).
13
Q
In chromatography, this depends on the distribution of a substance across the 2 phases:
A
- A substance moves far if it’s more attracted to the mobile phase.
- A substance doesn’t move far if it’s more attracted to the stationary phase.
14
Q
In chromatography, A substance moves far if it’s more attracted to the …
A
mobile phase.
15
Q
In chromatography, A substance doesn’t move far if it’s more attracted to the …
A
stationary phase.
16
Q
In chromatography, different components can sometimes be ———- to a solvent.
A
equally attracted
17
Q
Different components can sometimes be equally attracted to a solvent.
So, the number of spots a mixture produces can …
A
vary depending on the solvent used.
18
Q
What are the chromatography phases?
A
- mobile phase
- stationary phase
19
Q
In paper chromatography, mixtures of soluble substances are separated. A solvent (1.) is run through the mixture on paper (2.).
A
- mobile phase
- contains the stationary phase
20
Q
In chromatography, the substances will move up the paper at different rates. The most soluble substance will move the …
A
furthest.
21
Q
In chromatography, the components that travel furthest are highly soluble (dissolve easily) in the solvent. They are also ——– to the chromatography paper.
A
minimally attracted
22
Q
What are the steps of chromatography?
A
- Dip the bottom of the chromatography paper into the solvent.
- The solvent travels up the chromatography paper.
- As the solvent moves, it picks up and transports the substances being tested up the chromatography paper.
23
Q
What is the mobile phase in paper chromatography?
A
A solvent
24
Q
Chromatography produces …
A
chromatograms
25
We use chromatograms to identify compounds in mixtures by calculating ...
Rf value.
26
We use chromatograms to identify ...
compounds in mixtures by calculating Rf value.
27
Rf values =
distance travelled by substance / distance travelled by solvent
28
Rf values depends on the ...
solvent.
29
We can learn more about the identity of the components by ...
testing any references and the unknown mixture in a range of solvents.
30
A reference substance is a ----------------- These substances provide valuable evidence, but not proof.
pure sample that's run next to the tested substance to see if it's a component in the mixture.
31
A reference substance is a pure sample that's run next to the tested substance to see if it's a component in the mixture. These substances provide ...
valuable evidence, but not proof.
32
What 2 distances are important when calculating Rf values in chromatography?
- Distance travelled by substance
- Distance travelled by solvent
33
What does the process of chromatography produce that can be analysed?
chromatogram
34
what are the states of Chromatography phases?
- Mobile phase - Liquid or gas.
- Stationary phase - Solid or viscous liquid.
35
The mobile phase is...
the solvent
36
the stationary phase is ...
chromatography paper
37
What can we say if the Rf values of a reference and a spot match in all solvents?
It is very likely that the mixture contains the reference compound.
38
This practical investigates the use of paper chromatography in separating mixtures. The process is:
1. Use a pencil to draw a horizontal line near the bottom of the chromatography paper.
2. Place samples of known food colourings (A-D) next to an unknown substance (X) on this ‘start line’.
3. Place the paper in a beaker containing a small volume of solvent.
4. Let the solvent move to a few cm below the end of the paper.
5. By comparing spots produced by X with those produced by A-D, you will be able to identify the unknown substance.
39
Which direction does the solvent move in paper chromatography?
upwards
40
What are the apparatus required for paper chromatography?
- Chromatography paper
- Beaker
- Solvent
- Pencil
41
Place a ------------- close to the mouth of a test tube that contains a gas.
If the gas is hydrogen, a "squeaky pop" sound will be produced.
This noise is generated because hydrogen burns rapidly in the presence of oxygen to give H2O.
lit splint
42
Place a lit splint close to the mouth of a test tube that contains a gas.
If the gas is hydrogen, a "-----------" sound will be produced.
This noise is generated because hydrogen burns rapidly in the presence of oxygen to give H2O.
squeaky pop
43
Place a lit splint ------------------------
If the gas is hydrogen, a "squeaky pop" sound will be produced.
This noise is generated because hydrogen burns rapidly in the presence of oxygen to give H2O.
close to the mouth of a test tube that contains a gas.
44
A "squeaky pop" sound is generated when hydrogen burns rapidly in the presence of ----- to give water (h2o)
oxygen
45
A "squeaky pop" sound is generated when hydrogen burns rapidly in the presence of oxygen to give ...
water (h2o)
46
If a lit splint is held at the mouth of a test tube containing hydrogen, what will happen?
A squeaky pop sound will be produced
47
Insert a -------- into a test tube that contains a gas.
If the gas is oxygen, the splint will relight.
glowing splint
48
Insert a glowing splint -------------
If the gas is oxygen, the splint will relight.
into a test tube that contains a gas.
49
Insert a glowing splint into a test tube that contains a gas.
If the gas is oxygen, ...
the splint will relight.
50
What are the apparatus required when testing for oxygen?
- Test tube
- Glowing splint
51
What are the apparatus required when testing for hydrogen?
- test tube
- lit splint
52
Take an —————- and bubble through the gas.
If the gas is carbon dioxide, the limewater solution will turn from clear to cloudy.
aqueous solution of limewater (calcium hydroxide)
53
Take an aqueous solution of limewater (calcium hydroxide) and ーーーーー.
If the gas is carbon dioxide, the limewater solution will turn from clear to cloudy.
bubble through the gas
54
Take an aqueous solution of limewater (calcium hydroxide) and bubble through the gas.
If the gas is carbon dioxide, the 。。。
limewater solution will turn from clear to cloudy.
55
What are the apparatus required when testing for carbon dioxide
- Limewater
- test tube
56
Insert ———— into a test tube that contains a gas.
If the gas is chlorine, the litmus paper will bleach and change colour from red to white.
damp litmus paper
57
Insert damp litmus paper into a test tube that contains a gas.
If the gas is chlorine, the litmus paper will …
bleach and change colour from red to white.
58
Insert damp litmus paper into a test tube that contains a gas.
If the gas is ———-, the litmus paper will bleach and change colour from red to white.
chlorine
59
Insert damp litmus paper into a test tube that contains a —-.
If the gas is chlorine, the litmus paper will bleach and change colour from red to white.
gas
60
Insert damp litmus paper into ae that contains a gas.
If the gas is chlorine, the litmus paper will bleach and change colour from 1. to 2..
1. red.
2. white
61
Some metal ions can be identified using …
flame tests.
62
The following positive metal ions all produce a characteristic flame colour when burned:
- Copper (Cu2+)
- Lithium (Li+)
- Potassium (K+)
- Calcium (Ca2+)
- Sodium (Na+)
63
When Copper (Cu2+) is burned is produces a …
Green flame.
64
When Lithium (Li+) is burned is produces a …
Crimson flame
65
When Potassium (K+) is burned is produces a …
Lilac flame
66
When Calcium (Ca2+) is burned is produces a …
Orange-red flame
67
When Sodium (Na+) is burned is produces a …
Yellow flame
68
We can use flame tests to identify the metal ions in an …
ionic compound.
69
What are the steps Flame Test Practical
1. Submerge a nichrome wire loop in dilute hydrochloric acid to make sure that it is clean.
2. Place the nichrome wire loop into the sample to be tested.
3. Hold the nichrome wire loop in a Bunsen burner's blue flame.
4. Observe any change in colour of the Bunsen flame.
70
In flame tests, what must the nichrome wire loop be submerged in to be cleaned
Dilute hydrochloric acid
71
In flame tests, a wire loop that has been cleaned and dipped in the sample to be tested, should be held in the ——- flame of a Bunsen burner.
blue
72
What are the flame test apparatuses?
- Bunsen burner
- nichrome wire loop
73
Metal ions can be found in …
aqueous solutions of metal compounds.
74
Metal ions can precipitate out of solution when they react with a ———————. This produces insoluble solids (don't dissolve in water) called precipitates.
sodium hydroxide solution (NaOH).
75
Metal ions can precipitate out of solution when they react with a sodium hydroxide solution (NaOH). This produces ————————- called ...
- insoluble solids (don't dissolve in water)
- precipitates
76
Metal ions can be found in —————— of metal compounds.
aqueous solutions
77
Metal ions can be found in aqueous solutions of metal compounds. These ions can 1. out of solution when they react with a …
1. precipitate
2. sodium hydroxide solution (NaOH).
78
Metal ions can be found in aqueous solutions of metal compounds. These ions can precipitate out of solution when they react with a sodium hydroxide solution (NaOH). This produces …
insoluble solids (don't dissolve in water) called precipitates.
79
Magnesium ions (Mg2+) form the ——— precipitate magnesium hydroxide.
white
80
Mg2+(aq) + 2OH-(aq) →
Mg(OH)2(s)
81
Aluminium ions (Al3+) form the —— precipitate aluminium hydroxide.
white
82
Al3+(aq) + 3OH-(aq) →
Al(OH)3(s)
83
Unlike the other two white precipitates, aluminium hydroxide can be dissolved in ——. This produces a ...
Excess NaOH
colourless solution
84
Calcium ions (Ca2+) form the —— precipitate calcium hydroxide
white
85
Solutions of halide ions
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of
dilute nitric acid to produce
silver halide precipitates:
silver chloride is …
white
86
Solutions of halide ions
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of dilute nitric acid to produce
silver halide precipitates:
silver bromide is …
cream
87
Solutions of halide ions
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of
dilute nitric acid to produce
silver halide precipitates:
silver iodide is ...
yellow
88
Solutions of halide ions
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of
dilute nitric acid to produce
…
silver halide precipitates.
89
Solutions of —————
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of
dilute nitric acid to produce
silver halide precipitates.
halide ions
90
Solutions of halide ions
(chloride, bromide and iodide
ions) react with silver nitrate
solution in the presence of
———— to produce
silver halide precipitates.
dilute nitric acid
91
Solutions of halide ions (chloride, bromide and iodide
ions) react with ————- in the presence of dilute nitric acid to produce
silver halide precipitates?
silver nitrate solution
