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    What are the most common questions that comes up in OCR As Chemistry both Unit 1 and Unit 2?

    I know definitions of Relative Atomin Mass or Relative Isotopic Mass is one but give me some more !
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    (Original post by hafiz9711)
    What are the most common questions that comes up in OCR As Chemistry both Unit 1 and Unit 2?

    I know definitions of Relative Atomin Mass or Relative Isotopic Mass is one but give me some more !
    Heya, I'm going to put this in the chemistry forum for you as you should get more responses there.

    You should also check out the forum to see if there's any other threads there which might be helpful to you!

    http://www.thestudentroom.co.uk/forumdisplay.php?f=130
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    If you don't like my definitions, go boil your head. Just learn them all!

    atomic number the number of protons
    mass number the number of nucleons
    isotope atoms of an element with different numbers of neutrons and different masses
    isotopic mass the mass of an isotope compared to 1/12th of the mass of an atom of carbon-12
    relative atomic mass the weighted mean mass of one atom compared to 1/12th of the mass of an atom of carbon-12
    amount of substance the number of particles in a substance
    mole the amount of a substance which has the same number of particles as there are atoms in 12.0 g of carbon-12
    Avogadro constant, NA the number of particles per mole (6.02 ×1023 mol–1)
    molar mass the mass per mole of a substance (units g mol–1)
    empirical formula the simplest whole number ratio of atoms of each element present in a compound
    molecular formula the actual number of atoms of each element in a molecule
    first ionisation energy energy needed to remove an electron from each atom in one mole of gaseous atoms
    second ionisation energy needed to remove an electron from each ion in one mole of gaseous 1+
    energy ions
    orbital a region that can hold up to two electrons, with opposite spins
    ionic bonding electrostatic attraction between oppositely charged ions
    covalent bond a shared pair of electrons
    dative covalent bond a shared pair of electrons where both electrons are donated by one atom
    electronegativity the ability of an atom to attract the bonding electrons in a covalent bond
    metallic bonding the attraction of positive ions to delocalised electrons
    periodicity a repeating pattern across different periods
    disproportionation a reaction in which an element is simultaneously oxidised and reduced
    empirical formula the simplest whole number ratio of atoms of each element present in a compound
    molecular formula the actual number of atoms of each element in a molecule
    general formula the simplest algebraic formula of a member of a homologous series
    structural formula the minimal detail that shows the arrangement of atoms in a molecule
    displayed formula the relative positioning of atoms and the bonds between them
    skeletal formula the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
    homologous series a series of organic compounds having the same functional group but with each successive member differing by CH2
    functional group a group of atoms responsible for the characteristic reactions of a compound
    structural isomers compounds with the same molecular formula but different structural formulae
    stereoisomers compounds with the same structural formula but with a different arrangement in space
    E/Z isomerism an example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group
    cis-trans isomerism a special case of EIZ isomerism in which two of the substituent groups are the same
    ‘curly arrow’ the movement of an electron pair, showing either breaking or formation of a covalent bond
    hydrocarbon a compound of hydrogen and carbon only
    radical a species with an unpaired electron
    electrophile an electron pair acceptor
    nucleophile an electron pair donor
    enthalpy change enthalpy change when the number of moles of reactants as specified in the
    of reaction balanced equation react together
    of formation enthalpy change for the formation of one mole of compound from constituent elements
    of combustion enthalpy change when one mole of a substance is completely combusted
    bond enthalpy enthalpy change when one mole of bonds of gaseous covalent bonds is broken
    Le Chatelier’s Principal if a system at equilibrium is subjected to a small change, the equilibrium tends to shift so as to minimise the effect of the change
 
 
 
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