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BMAT > Chem > Flashcards

Chem Flashcards

1
Q

Alkaline Earth metals

A

Group 2 - 2 electrons in outer shell

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2
Q

When a metal is descended

A

They get more reactive

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3
Q

When a non-metal group is descended

A

They become less reactive

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4
Q

Lithium flame?

A

Crimson red flame when ignited

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5
Q

Lithium + cold water

A

Floats, no melting and dissolves to give lithium hydroxide + hydrogen gas

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6
Q

Sodium flame

A

Yellow-orange flame

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7
Q

Sodium + water

A

Much stronger and melts/quickly dissolves to produce sodium hydroxide

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8
Q

Potassium flame

A

Self-ignites to give a lilac flame

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9
Q

Potassium reaction with water

A

Moves rapidly on the surface and then quickly dissolves

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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)

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11
Q

Saturated solution

A

No more solute will dissolve at a given temperature

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12
Q

Gases

A

Become less soluble as temperature increases

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13
Q

Salts

A

Solubility increases with temperature

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14
Q

Group 1 melting points

A

Low for metals and decrease down the group (decrease in the strength of metallic bonding)

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15
Q

Alkali metals density

A

Low - increase down the group

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16
Q

Alkali metal hardness

A

Soft and become softer down the group

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17
Q

Alkali metal conductivity

A

Good conductors of water and electricity

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18
Q

Why does density increase?

A

Increasing masses of individual ion cores within metallic solids

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19
Q

Why do group 1 metals become softer?

A

Decreasing strength of metallic bonding within solid structures

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20
Q

Alkalis freshly cut

A

Shiny metals will react with oxygen and tarnish forming metal oxide

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21
Q

Potassium + water

A

So Exothermic that hydrogen spontaneously ignites and burns with a lilac flame

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22
Q

Bromine

A

Orange

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23
Q

Iodine

A

Brown

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24
Q

Why do melting points increase down non,E gases?

A

Size of intermolecular forces increase - number of electrons increase

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25
Q

Density increases

A

Increasing mass of the atoms

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26
Q

Electrolysis

A

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

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27
Q

Cathode

A

Reduction occurs

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28
Q

Anode

A

Oxidation

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29
Q

What electrodes are used?

A

Platinum - inert ; do not interfere with reactions occurring at the electrode, simply acts as a point of connection between electrical circuit and solution

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30
Q

Which of the following could NOT precipitate silver ions from a solution of AgNO3?

A

NaNO3 ; provides more nitrate ions that would not cause silver ions to precipitate

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31
Q

Decanting

A

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

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32
Q

Separating funnel

A

Used to separate two immiscible liquids ; they form two layers ; upper layer has lower density and then lower layer can be poured out

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33
Q

Fractional Distillation

A

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

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34
Q

Fractionating column

A

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

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35
Q

Evaporation and crystallisation

A

Not sensible to heat to dryness because solids may decompose if heated too strongly

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36
Q

Chromatography

A

Solvent rises through capillary action ; different components have a different tendency to adsorb to paper (stationary phase)

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37
Q

Rf

A

(Distance travelled by sample)/(distance travelled by solvent)

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38
Q

Lid on chromatography

A

Kept on the tank to ensure that atmosphere in tank has a saturated solvent vapour - prevents solvent from evaporating rather than rising

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39
Q

Centrifugation

A

Separate heterogenous mixtures based on differences in particle mass ; separates mixture of gases but more common to separate solids from liquids

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40
Q

Liquid + solid

A

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

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41
Q

Centrifugation used in medicine

A

Separate blood opponents like RBCs and platelets from plasma

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42
Q

Gas gas mixtures

A

Centrifugation or cryogenic distillation

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43
Q

Chromatography

A

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

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44
Q

Distillation

A

If liquid boils off at higher temperature than expected

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45
Q

Impure substance freezing point

A

Is lowered

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46
Q

Impure substances

A

Melt over a range of temperatures

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47
Q

Evaporation (impurity)

A

If solution is evaporated to dryness - any solid residue is a dissolved impurity

48
Q

Reaction between metal and acid

A

Only occurs if metal is more reactive than hydrogen

49
Q

Strong acid

A

Goes to completion - full dissociation in water (HCl, H2SO4 and HNO3)

50
Q

Weak acid

A

Reversible - carboxylic acids
Organic acids will react less rapidly and will have a higher ph than strong acids

51
Q

As the concentration of H+ ions decreases by a factor of 10

A

The ph value at increases by 1

52
Q

Monoprotic/diprotic/triprotic acids

A

HCl -> H+
H2SO4 -> 2H+
H3PO4 -> 3H+

53
Q

Strong base

A

Alkali which undergoes full dissociation in water (to completion)
Sodium hydroxide (releases OH-)

54
Q

Weak base

A

Partially dissociates (weak base)
Ammonia +H2O -> <- NH4+ + OH-

55
Q

Neutralisation

A

Exothermic - release heat to surroundings

56
Q

Bond forming

A

Releases energy

57
Q

Bond breaking

A

Needs energy

58
Q

Where do bend energies only apply?

A

To reactants and products that are in gaseous states

59
Q

Limitations of bond energies

A

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
Q

In aqueous solutions SHC?

A

SHC specific to to the substance being heated - in this case it is water

61
Q

When using q=mcΔt reactions?

A

Use moles of the limiting reactant
Use SHC of water
Use volume of total solution

62
Q

Errors when calculating combustion Enthalpy change?

A

Incomplete combustion
Dissipation to surroundings
Heat is lost to the calorimeter

63
Q

Power supply of electrolysis?

A

Must be dc so that current passes in one direction only

64
Q

Electrolysis if molten lead bromide

A

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
Q

Hydrogen gas during electrolysis?

A

Formed at negative electrode (cathode) if HYDROGEN IS LESS REACTIVE THAN CATION

66
Q

Metals less reactive than hydrogen

A

Copper silver gold platinum

67
Q

When is oxygen formed at the positive electrode?

A

Oxygen is formed at the anode UNLESS halide ions are present

68
Q

Electroplating

A

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
Q

Object to be electroplated

A

Is always made the negative electrode (cathode) to attract the positive ions

70
Q

Electrolyte during electroplating

A

Should contain the metal ions to be plated on to the jug

71
Q

Purification of copper using electrolysis?

A

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
Q

Hydrogen test

A

Burning splint is placed in hydrogen ; hydrogen burns to produce water - leads to a “squeaky pop” noise

73
Q

Oxygen test

A

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
Q

Carbon dioxide

A

Limewater is a solution of calcium hydroxide ; when carbon dioxide is bubbled through limewater - reacts to form insoluble calcium carbonate - this goes cloudy

75
Q

Chlorine test

A

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
Q

CO32- ions

A

React with acid to produce carbon dioxide ; effervescence is observed and thus can be confirmed using limewater

77
Q

Halide ions

A

Hydroxide and carbonate ions must be removed by adding excess dilute nitric acid

78
Q

Test for halide

A

Add silver nitrate ; precipitate (milk cream butter)

79
Q

Sulfate test

A

Barium nitrate/barium chloride to form a white precipitate

80
Q

Order of tests

A

Carbonate ions
Sulfate ions (HCl)
Halide ions (HNO3)

81
Q

Flame test

A

Thin wire is washed in acid (cleaned)
Dipped in unknown substance
Passed through blue flame
Metal cations change colour

82
Q

What metal is used in wire for flame test?

A

Nichrome or platinum because they have high melting points and are inert

83
Q

Flame test colours

A

Lithium = crimson red
Sodium = yellow/orange
Potassium = lilac
Calcium = red orange
Copper = green

84
Q

Group 1 metal hydroxides

A

More soluble down the group

85
Q

If sodium hydroxide added to a metal ion solution with a concentration more than 0.1 and not from group 1

A

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
Q

Neutralisation

A

Exothermic

87
Q

Crude oil

A

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
Q

Large molecules

A

High BP
Not very volatile
Do not flow easily
Do not ignite easily

89
Q

Second stage of refining process

A

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
Q

Condensation polymerisation

A

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
Q

Main types of condensation polymers

A

Polyesters/polyamides

92
Q

Ester is formed

A

Carboxylic acid + alcohol

93
Q

Polyamide

A

Carboxylic acid group combines with an amine NH2 ; molecule of water is eliminated
Nylon-6,6 is an example of a condensation polymerisation

94
Q

Biodegradable polymers

A

Degrease after indented use to produce natural products like CO2/N2/H2O - brought about by enzymes/microorganisms

95
Q

Most polymers

A

Non-biodegradable ; resistant to breakdown by microorganisms/enzymes due to strong bonding between carbon chains

96
Q

Sodium + ethanol/methanol (slow)

A

Formed sodium ethoxide + H2
Ethoxide ion being the C2H5O-
Organic bit written first as is for ethanoates

97
Q

Carboxylic acids

A

Weak - partially dissociate

98
Q

Carboxylic acid + alcohol

A

Ester + water
Concentrated sulfuric acid needed

99
Q

Why are group 1 metals more reactive than group 2?

A

Group 1 metals only need to lose 1 electron while group 2 need to lose 2 ; aluminium is even worse

100
Q

Ease of extraction of metals?

A

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
Q

Metals above carbon in reactivity

A

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
Q

Viable methods

A

Cheapest

103
Q

What is above carbon in reactivity

A

Potassium sodium calcium magnesium aluminium

104
Q

Alloy

A

Particles are different sizes and this disrupts structure - prevents them from sliding over one another - increases strength of the material

105
Q

Silver

A

Best thermal and electrical conductor of all metals

106
Q

Transition metals

A

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
Q

Testing for water

A

Solid copper Sulfate is white - turns blue when hydrated
CuSo4 + 5H2O -> CuSO4.5H2O(s)

108
Q

Gases in dry air

A

Nitrogen - 78.1%
Oxygen - 20.95%
Argon - 0.9%
CO2 - 0.04%

109
Q

Fractional distillation of air

A

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
Q

Separated oxygen

A

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
Q

Greenhouse gases

A

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
Q

Air pollution

A

Caused by release of poisonous/harmful chemicals into the air ; damage buildings/environment/living things etc

113
Q

Carbon monoxide

A

Incomplete combustion of fossil fuels (engines of cars/gas boilers etc)
Binds more strongly to haemoglobin than oxygen and reduces oxygen content

114
Q

Carbon dioxide

A

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
Q

Sulfur dioxide

A

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
Q

Oxides of nitrogen

A

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
Q

Chlorine and fluoride ions

A

Cl2 - added to sterilise water as it kills harmful bacteria
F- ions - fluoride helps protect against tooth decay

BMAT (7 decks)

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