CORRECTIONS Flashcards
| EXOTHERMIC reactants and products graph ?????? Check tutorial 8.2 | | | |\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
- arrow only has one arrow head which points downwards
- y axis labelled H not change in enthalpy
Periodic definition
Patterns in properties repeated across different periods
Periodic property of gaseous atoms of period 2 elements
Increase in FIRST IE as you go along the period.
Why does silicon have the highest melting point?
Giant structure
Lots of strong covalent bonds
So more energy in form of heat required to break them
Trend in electric conductivity from Na to Al
Bonding is metallic so more delocalised electrons per unit volume
Silicon ion formula
Si 4+
Why is the atomic radius of period 3 elements significantly larger than their period two counterparts (atomic radii of period 2 elements).
Period 3 elements have an extra full shell of electrons which repel each other occupying more space making the atomic radii larger.
Why is there no data on the atomic radius of argon ions?
Argon/any noble gas cannot form ions because TOO MUCH ENERGY IS REQUIRED
How many quantum shells?
4 - they’re the circles in my diagram explaining this, then within each circle is a sub shell and orbitals
How to work out number of outer shell electrons in an element if given its successive ionisation energies?
Where there is a big jump, that number of electron that has been removed is te number in the outer shell.
Why might the ionisation energy of an element below another elect be lower? Eg. gallium and aluminium
The lower down element’s electron that has to be removed is in a further out quantum shell which means it is further from the nucleus and better shielded so the force of attraction to the nucleus is weaker than the element above.
first IE equation
Al(g) —> Al+(g) + e-
What is the origin of London forces?
An instantaneous dipole induces another dipole.
Why does this branched alkane have a lower boiling point?
It is a branched alkane so has weaker London forces as the molecules cannot be as close together. So less energy required to break these bonds.
Why might a molecule without O, F or N not be able to form hydrogen bonds.
The molecule it does have is less electronegative than N, O or F so the molecule it does have (let it be S) has an S-H bond in the compound : but this S-H bond isn’t polar enough [no unevenly distributed electrons] to attract another S form another molecule so the hydrogen bond can form between those two compounds with the S’s joining together. WON’T ALWAYS BE AN S-H bond this is just the particular one here.
H
|
H-C-S-H
|
H
Why does methane have a higher volatility than methanol?
Methane doesn’t have oxygen so can’t form hydrogen bonds which are stronger. (So has a lower boiling point which equates to high volatility)
Lab test to prove something is polar?
Charged object near a jet of the substance, if its polar then the jet is deflected.
Why are methanol molecules polar?
The O-H bonds are polar because oxygen is very electronegative and this means it pulls electrons away, distorting the electron cloud which changes the bond angles causing it to be unsymmetrical.
Every polar molecule is unsymmetrical
Remember
Explanation of boiling points of hydrogen halides.
Boiling point increases from HCL down to HI because molecules have more electrons which means stronger London forces.
However, HF at the top of the halogens has the HIGHEST boiling point because it forms hydrogen bonds which are very strong.
Things with what dissolve well in each other??
Similar intermolecular forces
Hydrogen bonds only form with
F, N, O
How to prove that the formula of something produced. Is what they say it is.
- Work out the moles of each element
- work out ratio
How to form ionic equations
Split up aqueous substances into ions
Remove spectator ions
Half ionic equations electrons before and after arrows mean:
Electrons BEFORE arrow mean GAIN
Electrons AFTER arrow mean LOSS
How to convert from m3–>cm3.
X1 000 000
What determines if an ionic compound is soluble.
If the energy required to break up the lattice is made up by the energy released through hydration of ions.
