past paper stuff Flashcards
how do London forces arise ???
- uneven distribution of electrons
- creates instantaneous (temporary) dipole
- dipole is induced
what is the name given to repeating pattern of properties along a period ?
periodicity
what to remember with all calculations ?
does it ask for sig figs / decimal places ??
what does xH2O represent ?
water of crystallisation
what is a salt ?
metal /ammonium ion replaces H+ ion in an acid
define dative covalent bond
both electrons donated from same atom
define isotope
atoms of an element with same no of protons, diff no of neutrons
why do isotopes have similar chemical properties ?
same no. of electrons in outer shell
what to remember when drawing H bonds
lone pairs on Oxygen
what are conditions needed to make bleach ?
cold dilute NaOH
what is the 2nd product of metal + water/acid ?
hydrogen
what is meant by ionic lattice ?
repeating pattern of oppositely charged ions
pV =
nRT
what are the units of pressure in pV =
Pa
what are the units of volume in pV =
m3
what are the units of temp in pV =
kelvin
what is R in pV=
8.314 J / K / mol
what does roman numerals show
oxidation number
state two methods of carbon capture and storage
- react with metal oxide to for metal carbonate
- deep in ocean
what are (2) factors of greenhouse effect of a gas ?
- abundance
- ability to absorb IR
to be soluble in water, molecule must be able to …
form H-bonds with water
what is the oxidation of alcohols observation ?
orange to green
give two reasons why radical substitution produces a mixture of organic products
- further substitution
- substitution at diff positions along chain
give two reasons why enthalpy change of combustion isn’t very accurate
- incomplete combustion may occur
- water / alcohol may evaporate
when describe IR spectroscopy… what to remember
- IR absorbance at …
- no absorbance at …
what is a Brownsted-Lowry acid?
proton donor
what observation for phenol + bromine ?
- decolourises
- white ppt forms
what gets oxidised and reduced in disproportionation ?
ELEMENT
what are the conditions for formation of bleach ?
cold dilute (NaOH)
suggest two reasons for why radical sub produces many products
- further sub
- sub at diff positions on chain
what are two factors of greenhouse effect of gas ?
- conc
- ability to absorb IR
state a biodegradable alternative for CFCs
hydrocarbon
what is co solvent for testing for halides ?
warm ethanol
What name is given to the process by which components in a mixture are
separated during gas/liquid chromatography?
Partition
define average bond enthalpy
energy required to break 1 mol of bonds in gaseous molecules
what to remember w/ rate constant ?
UNITS
when forming mechanism for rate determining step thing, what must you not do ?
no intermediate electrons
state two advantages of fuel cells compared w/ fossil fuel combustion
- more efficient
- less CO2
why is benzoic acid less reactive than benzene ?
COOH is electron withdrawing group, so decreases electron density
how is conc of ozone maintained ?
O2 + O – O3
O3 – O2 + O
rate of O3 decomp = O3 formation
state a disadvantage (apart from storage) of hydrogen fuel for fuel cell
hydrogen is explosive
state a important difference between electrochemical and fuel cell
fuel cell requires constant fuel supply
suggest why some people think use of hydrogen as fuel consumes more energy than fossil fuels
energy needed to make hydrogen
what is the important factor when choosing suitable indicator ?
equivalence point matches pH range of indicator
define relative atomic mass
weighted mean mass of an ATOM compared w/ 1/12th mass of carbon-12
define electronegativity
ability of an atom to attract electrons in a covalent bond
define covalent bond
strong electrostatic attraction between shared pair of electrons and nuclei of bonded atoms
why is benzoic acid less reactive than benzene ?
-COOH is an electron withdrawing group so decreases electron density
state 3 differences between Benzene and Kekule
- hydrogenation of bonds less exothermic than expected
- all bond lengths the same
- requires high temp / halogen carrier (catalyst) for reaction
state the difference of electrons between benzene and cyclohexene
cyclohexene - localised electrons
benzene - delocalised electrons (can’t polarise molecules)
what is the HNMR standard ?
TMS
why is benzene hydrogenation enthalpy less exo ?
benzene is more stable
why are catalysts good ? (list)
- can use reactions w/ less waste
- less energy needed as no high temp
- less fossil fuels used up
how to get nitro group on phenol, directed to carbon 2 ?
low temp (lower than 50)
state the reason for benzenes stability
- delocalised rings above and below plane spread out negative charge
- reluctant to undergo addition
state conditions for alkene –> alcohol
steam, solid H3PO4 acid catalyst
describe how to purify sample of X w/ separation
- add sodium carbonate to remove acid catalyst
- transfer to separating funnel and remove bottom layer
- add drying agent (mag sulfate)
- re distill at B.P. (or filter)
