Chem Flashcards
1
Q
Alkaline Earth metals
A
Group 2 - 2 electrons in outer shell
2
Q
When a metal is descended
A
They get more reactive
3
Q
When a non-metal group is descended
A
They become less reactive
4
Q
Lithium flame?
A
Crimson red flame when ignited
5
Q
Lithium + cold water
A
Floats, no melting and dissolves to give lithium hydroxide + hydrogen gas
6
Q
Sodium flame
A
Yellow-orange flame
7
Q
Sodium + water
A
Much stronger and melts/quickly dissolves to produce sodium hydroxide
8
Q
Potassium flame
A
Self-ignites to give a lilac flame
9
Q
Potassium reaction with water
A
Moves rapidly on the surface and then quickly dissolves
10
Q
How to figure out position on periodic table
A
Number of numbers = period
Group = number of electrons in outer shell (7 or IUPAC group 17)
11
Q
Saturated solution
A
No more solute will dissolve at a given temperature
12
Q
Gases
A
Become less soluble as temperature increases
13
Q
Salts
A
Solubility increases with temperature
14
Q
Group 1 melting points
A
Low for metals and decrease down the group (decrease in the strength of metallic bonding)
15
Q
Alkali metals density
A
Low - increase down the group
16
Q
Alkali metal hardness
A
Soft and become softer down the group
17
Q
Alkali metal conductivity
A
Good conductors of water and electricity
18
Q
Why does density increase?
A
Increasing masses of individual ion cores within metallic solids
19
Q
Why do group 1 metals become softer?
A
Decreasing strength of metallic bonding within solid structures
20
Q
Alkalis freshly cut
A
Shiny metals will react with oxygen and tarnish forming metal oxide
21
Q
Potassium + water
A
So Exothermic that hydrogen spontaneously ignites and burns with a lilac flame
22
Q
Bromine
A
Orange
23
Q
Iodine
A
Brown
24
Q
Why do melting points increase down non,E gases?
A
Size of intermolecular forces increase - number of electrons increase
25
Density increases
Increasing mass of the atoms
26
Electrolysis
Electrolyte is a mixture of mobile ions - direct current is applied using two electrons
Positive ions attracted to negative cathode
Negative ions attracted to positive anode
27
Cathode
Reduction occurs
28
Anode
Oxidation
29
What electrodes are used?
Platinum - inert ; do not interfere with reactions occurring at the electrode, simply acts as a point of connection between electrical circuit and solution
30
Which of the following could NOT precipitate silver ions from a solution of AgNO3?
NaNO3 ; provides more nitrate ions that would not cause silver ions to precipitate
31
Decanting
Solid and liquid separated : solid will settle to the bottom and all that is required is a steady hand to carefully pour the liquid without disturbing the solid
32
Separating funnel
Used to separate two immiscible liquids ; they form two layers ; upper layer has lower density and then lower layer can be poured out
33
Fractional Distillation
Separates miscible liquids (ones soluble in each other) ; mixture is heated and when temperature of mixture reaches boiling point of component with lowest boiling point ; it rises up the fractionating column towards condenser where it is collected
Them or,enter used to monitor the temperature of vapour being condensed
34
Fractionating column
Provides a surface for condensing - higher boiling point is more likely to condense on glass beads in column ; continual evaporation and condensing on glass beads
Separation of two liquids occurs all the way up the fractionating column
35
Evaporation and crystallisation
Not sensible to heat to dryness because solids may decompose if heated too strongly
36
Chromatography
Solvent rises through capillary action ; different components have a different tendency to adsorb to paper (stationary phase)
37
Rf
(Distance travelled by sample)/(distance travelled by solvent)
38
Lid on chromatography
Kept on the tank to ensure that atmosphere in tank has a saturated solvent vapour - prevents solvent from evaporating rather than rising
39
Centrifugation
Separate heterogenous mixtures based on differences in particle mass ; separates mixture of gases but more common to separate solids from liquids
40
Liquid + solid
Solid particles settle to the bottom as they are more dense ; thus encourages settling by spinning the mixture at high speed in a horizontal circle - heaviest particles settle out first becoming a pellet
Remaining liquid may be pure - this is called the supernatant and it may be decanted into a new tube/spun at higher speed to separate the smaller particles
41
Centrifugation used in medicine
Separate blood opponents like RBCs and platelets from plasma
42
Gas gas mixtures
Centrifugation or cryogenic distillation
43
Chromatography
Different rf values indicates impurity
But impurity might have the same rf value as a desired compound by coincidence so not possible to be 100% sure of purity after analysis
44
Distillation
If liquid boils off at higher temperature than expected
45
Impure substance freezing point
Is lowered
46
Impure substances
Melt over a range of temperatures
47
Evaporation (impurity)
If solution is evaporated to dryness - any solid residue is a dissolved impurity
48
Reaction between metal and acid
Only occurs if metal is more reactive than hydrogen
49
Strong acid
Goes to completion - full dissociation in water (HCl, H2SO4 and HNO3)
50
Weak acid
Reversible - carboxylic acids
Organic acids will react less rapidly and will have a higher ph than strong acids
51
As the concentration of H+ ions decreases by a factor of 10
The ph value at increases by 1
52
Monoprotic/diprotic/triprotic acids
HCl -> H+
H2SO4 -> 2H+
H3PO4 -> 3H+
53
Strong base
Alkali which undergoes full dissociation in water (to completion)
Sodium hydroxide (releases OH-)
54
Weak base
Partially dissociates (weak base)
Ammonia +H2O -> <- NH4+ + OH-
55
Neutralisation
Exothermic - release heat to surroundings
56
Bond forming
Releases energy
57
Bond breaking
Needs energy
58
Where do bend energies only apply?
To reactants and products that are in gaseous states
59
Limitations of bond energies
Average values and not specific to molecules used (thus difference may be over 10%)
Can only be done for those reactions entirely in the gaseous state
60
In aqueous solutions SHC?
SHC specific to to the substance being heated - in this case it is water
61
When using q=mcΔt reactions?
Use moles of the limiting reactant
Use SHC of water
Use volume of total solution
62
Errors when calculating combustion Enthalpy change?
Incomplete combustion
Dissipation to surroundings
Heat is lost to the calorimeter
63
Power supply of electrolysis?
Must be dc so that current passes in one direction only
64
Electrolysis if molten lead bromide
Easy - cations attracted to cathode to form lead
Bromide anions are attracted to anode to form molecules of bromine gas (lose electrons - oxidised) - brown fumes
65
Hydrogen gas during electrolysis?
Formed at negative electrode (cathode) if HYDROGEN IS LESS REACTIVE THAN CATION
66
Metals less reactive than hydrogen
Copper silver gold platinum
67
When is oxygen formed at the positive electrode?
Oxygen is formed at the anode UNLESS halide ions are present
68
Electroplating
Anode is silver (not inert)
Silver atoms lose an electron to become cations
At the cathode these Ag+ ions each gain an electron (reduced) to form silver atoms which plate on to the object
69
Object to be electroplated
Is always made the negative electrode (cathode) to attract the positive ions
70
Electrolyte during electroplating
Should contain the metal ions to be plated on to the jug
71
Purification of copper using electrolysis?
Small piece of pure copper is chosen at the cathode ; anode and electrolyte supply Cu2+ ions for electrolysis
At the anode - copper atoms are oxidised to form Cu2+ ions ; half equation is Cu -> Cu2+ + 2e-
Cathode - these cu2+ ions gain electrons to form copper atoms which are a plated on to the pure copper electrode
72
Hydrogen test
Burning splint is placed in hydrogen ; hydrogen burns to produce water - leads to a “squeaky pop” noise
73
Oxygen test
Requires a glowing splint ; if a burning splint is blown out to leave red glowing embers - if this splint is added to a tube containing oxygen, it relights
74
Carbon dioxide
Limewater is a solution of calcium hydroxide ; when carbon dioxide is bubbled through limewater - reacts to form insoluble calcium carbonate - this goes cloudy
75
Chlorine test
Piece of damp blue litmus paper ; chloride forms an acidic solution which turns litmus red - chlorine is also a bleach so read and blue colours will both fade to leave a white colour
76
CO32- ions
React with acid to produce carbon dioxide ; effervescence is observed and thus can be confirmed using limewater
77
Halide ions
Hydroxide and carbonate ions must be removed by adding excess dilute nitric acid
78
Test for halide
Add silver nitrate ; precipitate (milk cream butter)
79
Sulfate test
Barium nitrate/barium chloride to form a white precipitate
80
Order of tests
Carbonate ions
Sulfate ions (HCl)
Halide ions (HNO3)
81
Flame test
Thin wire is washed in acid (cleaned)
Dipped in unknown substance
Passed through blue flame
Metal cations change colour
82
What metal is used in wire for flame test?
Nichrome or platinum because they have high melting points and are inert
83
Flame test colours
Lithium = crimson red
Sodium = yellow/orange
Potassium = lilac
Calcium = red orange
Copper = green
84
Group 1 metal hydroxides
More soluble down the group
85
If sodium hydroxide added to a metal ion solution with a concentration more than 0.1 and not from group 1
Precipitates will form
Mg 2+ = white
Calcium = white
Aluminium = white (dissolves in excess sodium hydroxide giving a colourless solution)
Copper = blue
Iron (2+) = green (will turn brown as it oxides in air)
Fe3+ = brown
86
Neutralisation
Exothermic
87
Crude oil
Complicated mixture of many hydrocarbon molecules ; needs to be refined - starts with fractional distillation (vaporised and passed into a column which is hot at the bottom and cool at the top ; rise until they reach a point where temperature is below their boiling point - here they condense)
88
Large molecules
High BP
Not very volatile
Do not flow easily
Do not ignite easily
89
Second stage of refining process
Production of more of the shorter chain molecules ; catalytic cracking - longer chain molecules are passed over a heat catalyst and broken down into shorter ones
Produce smaller hydrocarbons - some of which are Alkenes
90
Condensation polymerisation
A small molecule of H2O or HCl is eliminated each time a linkage is made ; often involves different types of monomer molecules with each monomer must have at least 2 functional groups to form linkages at different positions in the molecule
91
Main types of condensation polymers
Polyesters/polyamides
92
Ester is formed
Carboxylic acid + alcohol
93
Polyamide
Carboxylic acid group combines with an amine NH2 ; molecule of water is eliminated
Nylon-6,6 is an example of a condensation polymerisation
94
Biodegradable polymers
Degrease after indented use to produce natural products like CO2/N2/H2O - brought about by enzymes/microorganisms
95
Most polymers
Non-biodegradable ; resistant to breakdown by microorganisms/enzymes due to strong bonding between carbon chains
96
Sodium + ethanol/methanol (slow)
Formed sodium ethoxide + H2
Ethoxide ion being the C2H5O-
Organic bit written first as is for ethanoates
97
Carboxylic acids
Weak - partially dissociate
98
Carboxylic acid + alcohol
Ester + water
Concentrated sulfuric acid needed
99
Why are group 1 metals more reactive than group 2?
Group 1 metals only need to lose 1 electron while group 2 need to lose 2 ; aluminium is even worse
100
Ease of extraction of metals?
Position of metal in reactivity series
Metals below carbon in reactivity series can be extracted from their ores by reduction using carbon or carbon monoxide (iron ore)
101
Metals above carbon in reactivity
Cannot be extracted using carbon and therefore must be extracted using electrolysis - electricity is sued to break down molten ionic compounds into ions and they are attracted to cathode
This is very expensive
102
Viable methods
Cheapest
103
What is above carbon in reactivity
Potassium sodium calcium magnesium aluminium
104
Alloy
Particles are different sizes and this disrupts structure - prevents them from sliding over one another - increases strength of the material
105
Silver
Best thermal and electrical conductor of all metals
106
Transition metals
Form stable ions in different oxidation states
They are very useful catalysts
Often coloured because they absorb visible light of a particular wavelength and then reflect off the complementary colour
107
Testing for water
Solid copper Sulfate is white - turns blue when hydrated
CuSo4 + 5H2O -> CuSO4.5H2O(s)
108
Gases in dry air
Nitrogen - 78.1%
Oxygen - 20.95%
Argon - 0.9%
CO2 - 0.04%
109
Fractional distillation of air
Liquids with different boiling points are separated ; air has to be cold enough to condense to a liquid
Compress the air to 150 times atmospheric pressure ; passed over pipes carrying cold water
Carbon dioxide and water are now removed from the mixture (they are now solids) otherwise they would block the fine jets used in the expansion phase
110
Separated oxygen
Used to increase the supply of oxygen to people with impaired lung function or wounds that are difficult to deal with in hospital (also removes impurities from iron in steel making)
111
Greenhouse gases
Carbon dioxide, methane and water vapour
Greenhouse gases allow short wavelength radiation such as UV/visible to pass through and heat the surface of the earth ; as the earth cools it emits longer wavelength radiation such as IR
CO2 and CH4 absorb IR and this is trapped in the atmosphere and temperature rises
Increase of co2 by deforestation and burning
Increase of methane by rice field and cattle farming/landfill sites
112
Air pollution
Caused by release of poisonous/harmful chemicals into the air ; damage buildings/environment/living things etc
113
Carbon monoxide
Incomplete combustion of fossil fuels (engines of cars/gas boilers etc)
Binds more strongly to haemoglobin than oxygen and reduces oxygen content
114
Carbon dioxide
Enters the air through respiration/decay and dissolved CO2 escaping from sea water
Removed from the air via photosynthesis and co2 dissolving in water
115
Sulfur dioxide
Oxidised to give sulfur dioxide ; poisonous, colourless, acidic
Reacts with water and oxygen to produce sulfuric acid (acid rain)
Can cause asthma attacks (so2)
S + O2 -> SO2
116
Oxides of nitrogen
High temperatures/pressures in car engines for example ; can give different oxides of nitrogen NOx
React with oxygen and water in atmosphere to generate nitric acid (acid rain)
Trigger asthma attacks and are toxic
117
Chlorine and fluoride ions
Cl2 - added to sterilise water as it kills harmful bacteria
F- ions - fluoride helps protect against tooth decay
