Vianca Flashcards
Comparing melting / boiling points of 2 compounds (4)
1) State the structure of both of the compounds eg giant ionic / simple molecular – these are in the textbook
2) State what type of bonding each of these structures possesses – eg London forces / hydrogen bonding etc
3) State which one is stronger / weaker – or in the event of two of the same forces, which one is stronger because there are more of them?
4) Link this to energy – state how this affects the energy to break/overcome
Remember that if the question is about ice vs water – ice is a 3D structure with hydrogen bonding and molecules close together – when ice is melted, ice loses its regular crystal arrangement (the H bonds do not break). But when water is boiled, the H bonds do break.
Successive ionisation energies
Make sure to say where there is a large difference between the ionisation energies eg. Between 1st and 2nd as your reasoning
Reducing random error (this is a new spec standard)
Repeat until results concordat and then calculate mean
Reducing percentage uncertainty
Increase increase increase! Greater mass, greater Burette size etc
CIP
Take each C atom individually. State which is the highest priority on each one
Cis/trans
Take each C atom individually and look at how many of the Hs attached to each carbon atom
Stereoisomerism definition
Need 2 different functional groups of each C atom attached to a C=C
Standard enthalpy changes…
These are not official definitions – these are the parts that will be in bold on the mark scheme (and the stuff students always forget and is the reason why they lose marks)
Of combustion – say words completely combusts (completely burns) in excess / pure O2
Of neutralization – production 1 mole of liquid water
Of reaction – remember all reactants and products are in their standard states
Of formation – for formation of 1 mol of compound + produced from consistuent / substituent elements
Le chatlier question – temp / pressure / compromise
Temp:
1) State what the enthalpy change is (positive / negative)
2) State what this means – is the forward reaction exo/ endo
3) State what happens when you decrease the temp (in the case of forward exo this is the best way to attack the q) – what is the shift of position of equilibrium
If forward is endo. Then state what happens if you increase temp
4) How does this shift influence conc of products and conc of reactants
5) How does this shift affect (percentage) yield
6) What is the problem with decreasing temp
7) Compromise – need a sufficiently high temp to produce a sufficient rate of reaction but still low enough to produce sufficient yield (if the forward reaction is exo then this definition works). If forward reaction endo – then you’re fine on both sides, increasing temp increases RoR and % yield (so no need to compromise)
Pressure
1) State which side has more gaseous molecules / molecules (add a numerical ratio is good)
2) State what happens if you increase the pressure – link this to statement 1
3) Repeat steps 3-5 as in the temperature paragraph above
4) Pressure and RoR?
5) Any compromise – if decreasing pressure increases yield then of course it’s a compromise between RoR, consider compromise between RoR/yield vs safety risks / costs
Boltzmann distribution
Boltzmann
Just remember to consider area under the curve – everyone forgets this and draw a diagram with the area in between shaded in (with excess molecules greater / equal to Ea labelled)
Relative masses
Remember these are weighted mean masses of an atom relative to 1/12th of a c-12 atom
Questions on conductivity
If an element / compound is given – 1) state what it conducts in (ie solid / liquid / aqueous) and what it doesn’t conduct electricity in
State why – delocalised electrons / mobile ions or charge carriers etc / fixed ions for all of these arguments
3) state the structure of your element / compound – giant metallic / ionic lattice etc
4) state what bonds there are in the structure
Ionisation energy questions
Refer to these words in your answer Nuclear attraction and define this Nuclear charge (if relevant) and number of protons Shielding – (are electrons in same shell?) Number of shells How is number of electrons changed Atomic radius Reactivity Ease of removal of electron
How is the attraction of electrons changing if you are doing something to it (ie across a period etc)
Hydrogen bonding diagrams
Draw dipoles on every atom – H bond is dotted line
Need a lone pair of electrons on O atom
Ice / water questions
Describe the property of ice – eg less dense but also remember to explain it using the argument of bonds and structure it has
Salt making
Remember H ions are replaced by metal ions
Metal / acid reaction observation
Describe what happens – ie what do you see and then describe what is formed (what sort of solution)
Bond enthalpy
Remember average bond enthalpies are an average and are always endothermic as they require energy to break
Remember that these are not always the same – learn why these can vary (it is in your textbook!)
Radical substitution
Write this
Initiation : the step
Propagation : the step
(Quote what happens during propagation and catalyst is the radical)
Termination : the step
Why does termination happen? At how many number of molecules will this happen? At what point (in terms of concentrations) does this happen – all in your textbook!
If necessary – extra further substitution steps / substitution at different points on chain can drop % yield (if q asks for limitations of radical substitution)
Mass spec questions
State the peak value
Then explain what this shows
Eg [ch3]+ = 15 and peak I is 15 or something like that to show peak I is Ch3
Don’t forgot the positive sign and square brackets – people lose silly marks because of this!
