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Common As Chemistry questions

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 !

Reply 1

Puddles the Monkey

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. :smile:

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

Reply 2

Pigster

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, N_A 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