unit 2 definitions

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  • Created by: Yasmin
  • Created on: 25-04-13 22:32
enthalpy change (... H)
the heat energy change measured under conditions of constant pressue
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standard enthalpy change - standard conditions
pressure 100kPa temperature 298k
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standard enthalpies of combustion
is the enthalpy change when one mole of compund is completely burned in oxygen under standard conditions, all reactants and products in their standard states
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standard enthalpies of formation
is the enthalpy change when one mole of compound is formed from its constituent elements under standard conditions, all reactants & products in their standard states
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heat change
q= m c ... T
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calculating enthalpy change for combustion
..
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calculating enthalpy change for formation
...
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reactions can only occur when ..
collisions take place between particles having sufficient energy
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activation energy
the minimum energy that a particle needs in order to react
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catalyst
substance that affect the rate of chemical reactions without being chemically changed themselves
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effect of temp on rate of reaction
increases - greater prrportion of particles have a higher activation energy, so more successful collisions
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effect of conc on rate of reaction
increases rate of reaction - increasing the conc results in more frequent collions
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how a catylst works
increases rate f reaction by providing an alternative reaction pathway with a lower activation energy
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dynamic nature of equilibria
althought the concentrations of reactants and products remain the constant, both forward and reverse reactions are still proceeding at equal rates
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oxidation
is the process of electron loss
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oxidising agents are..
electron acceptors
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reduction
is the process of electron gain
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reducing agents are...
electron donors
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oxidation numbers
F (-1) O (-2) H (+1) Na (+1) Cl (-1)
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group 7 (the halogens) electronegativity
DECREASES - more electron shells , nuclear charge decrease, bigger atom
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group 7 (the halogens) bp
INCREASE larger molecules, larger VDW's forces
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group 2 (alkaline earth metals) atomic radius
INCREASE - additional level of electrons
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group 2 (alkaline earth metals) first ionisation energy
DECREASE- atoms larger, outmost elecrtons futher away from nucleus, increase shielding
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group 2 (alkaline earth metals) mp
DECREASE - strength of metallic bonding decreased, atoms larger distance between delocalised electrons and nucleus
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Mg-Ba reaction with water
INCREASE - metals more reactive/vigouros
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realtive soubilities of HYDROXIDIES
MORE SOLUBLE -Mg(OH)almost insoluble as a suspension in water it is a solid rather than in a solution
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Mg(OH)
'milk of magnesia' used in indigestion remedies to neutralise excess stomach acid
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Ca(OH)
'slaked lime' used to treat acidic soil
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relative solubilities of sulfates Mg-Ba
DECEASE- less soluble Ba is almost insoluble
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acidified BaCl
used as a reagent to test for sulfate ions (the addition of acid removes carbonate ions as carbondioxide
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BaSO
'barrium meal' taken by the mouth to outline the gut in medicine x-rays
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mechanism of methane with chlorine
free-radical SUBSTITUTION (1st Initiation, 2nd Propagation, 3rd Termination)
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chlorine atoms catalyse the decomposition of ..
ozone and contribute to the formation of a hole in the ozone layer
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how/why are chlorine atoms found in the upper atmosphere
when energy from ultra-violet radiation causes C-Cl bonds in chlorofluorocarbons (cfs) to break
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haloalkanes (contain what bond)
polar bonds
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alkenes
unsaturated hydrocarbons
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bonding in alkenes involves what bond
double bond
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>C=C<
planar
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E Stereoisomerism
opposite sides
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Z Stereoisomerism
same sides
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double bond in an alkene is a centre of ....
high electron density
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polymerisation of alkenes
long chain molecules made up from jining together small molecules called monomers
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poly(alkenes) like alkanes are..
unreactive
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poly(ethene) typical uses
washing up bowls, plastic bags
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poly(propene) typical uses
rope (is recycled)
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how is ethanol produced by fermentation
carbohydrates from plants are broken down into sugars & then converted into ethanol by the action of enzymes from yeast ANAEROBIC RESPIRATION
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conditions for fermentation (2)
zymase , 40 degrees
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economic and environmental advantages and diadvantages of fermentation
renewable, produces CO2 (carbon neutral biofuel)
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economic and environmental advantages and diadvantages of the industrial production from ethene
non renwable sources, high temp and high pressure $$$
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biofuel
.
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carbon neutral
an activity that has no net annual cabon(green house gas) emmissions to the atmosphere
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teritory alcohols are not easily ...
oxidised, oxidation would need a C-C bond to break, rather than a C-H (ketones do not oxidise for the smae reason)
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primary alcohols can be oxidised to
aldehydes & further to carboxyic acids
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secondry alcohols can be oxidised to
ketones
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The Tollens (silver mirror) test
it is a solution of silver nitrate in aq ammonia. it oxidsises aldehydes but not ketones. as aldehyde is oxidised the colourless silver compounds are reduced to a metallic silver
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alkenes can be formed from alcohols by acid catalysed
ELIMINATION - appriciate that this method provides a possible route to polymers without using monomers dervied from oil
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high resolution mass spectrometry can be used to...
determine the molecular formula of a compound from the accurate mass of a molecular ion
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fingerprinting
a unique set of peaks (caused by complex vibrations) can be used to identify the chemical (between 1400cm-1 - 800cm-1
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Other cards in this set

Card 2

Front

pressure 100kPa temperature 298k

Back

standard enthalpy change - standard conditions

Card 3

Front

is the enthalpy change when one mole of compund is completely burned in oxygen under standard conditions, all reactants and products in their standard states

Back

Preview of the back of card 3

Card 4

Front

is the enthalpy change when one mole of compound is formed from its constituent elements under standard conditions, all reactants & products in their standard states

Back

Preview of the back of card 4

Card 5

Front

q= m c ... T

Back

Preview of the back of card 5
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