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Higher Chemistry End of Year

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  • What is the trend in ionisation energy down a group? Explain why.
    It decreases - because of the shielding effect which reduce the attraction between the nucleus and the outer electrons.
  • What stage of the free radical chain reaction is this?
    Initiation
  • What could I do to the pressure conditions to maximise the yield of ammonia?
    Increase
  • What are the three stages of a free radical chain reaction?
    Initiation, propagation, termination
  • Why do we use a water bath when preparing an ester?
    Because the reactants and products are flammable.
  • What TWO signs would we see that an ester has formed?
    An aroma is produced; an oily layer will appear on top of the mixture.
  • Which group of the Periodic Table has elements which are monatomic?
    Noble gases
  • What name is given to this type of reaction?
    Hydration
  • Whose "law" is defined as the total enthalpy change of a reaction is the same regardless of the route taken?
    Hess's Law
  • Name this ester.
    Ethyl butanoate
  • What is the weakest intermolecular force?
    London dispersion forces
  • What two factors affect how different substances are separated in a chromatography experiment?
    Molecule size and polarity
  • Its chemical formula is C5H8, and is the basis of all terpenes. What is the name is this molecule?
    Isoprene (2-methylbuta-1,3-diene)
  • Name the ester formed when propanol reacts with pentanoic acid.
    Propyl pentanoate
  • What is a free radical?
    Highly reactive atoms or molecules with unpaired electrons.
  • Which is the odd one out: boron, carbon, silicon, phosphorus
    Phosphorus - the rest exist as covalent networks.
  • What functional group is present in aldehydes and ketones?
    Carbonyl group
  • What process could I use to separate different gases in a mixture?
    Distillation
  • Explain why the melting points of halogens increase as you go down the group.
    More electrons = more london dispersion forces = more energy needed to break these forces = higher melting point.
  • Define "electronegativity".
    A measure of an atom's attraction for electrons in a covalent bond.
  • A hydrogen bond forms when hydrogen is directly bonded to any of which three elements?
    Nitrogen, oxygen or fluorine
  • If two atoms are bonded with the same electronegativity, what kind of bond is this?
    Pure covalent / non-polar covalent
  • Define "ionisation energy".
    The energy required to remove one mole of electrons from one mole of gaseous atoms.
  • Explain why oils have lower melting and boiling points than fats.
    More double bonds, resulting in "kinks" in the molecules, leading to them packing less tightly together, leading to weaker LDFs.
  • What two types of molecules can react together to form an ester?
    An alcohol and a carboxylic acid
  • What phrase describes the energy required to start a chemical reaction by breaking bonds in the reactants?
    Activation energy
  • A chemical reaction takes 10 seconds. What is the relative rate of this reaction?
    0.1 s-1
  • Name this molecule.
    3-methylpentane
  • Give the systematic name of glycerol.
    Propane-1,2,3-triol
  • Identify the oxidising agent.
    Cu2+ ions
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