Question types Flashcards
VSEPR: predicting stability of the same compound with different molecular arrangements
Swap lone pairs and bond pairs with between the axial and equatorial positions. (to create the different arrangements)
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lp - lp > lp - bp > bp - bp
ax - ax : 180
ax - eq: 90 (most significant repulsion)
eq - eq: 120
Since ax - eq has the most significant repulsion given the small angle between them, we just need to take note of the lp/bp with this arrangement.
Count the number of lplp, bpbp, and lpbp repulsions in each molecule.
Conclude with “By VSEPR, lp-lp > lp-bp>bp-bp. Hence the relative stabilities of the molecules are ordered as such, …”
Describing types of IMF
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Comparison of bp/mp via bonding
3 types of IMF: id-id, pd-pd, hydrogen bonding
ID-ID INTERACTIONS are formed via the uneven distribution of electron cloud which induces a short lived dipole in the neighbouring molecule
PD-PD INTERACTIONS are formed between polar molecules with permanent dipoles due to the electrostatic attraction between the delta positive end of one molecule and the delta negative end of another molecule.
STAR: Structure, Type (of IMF), A
How to deduce that the reaction between two or more reagents form a buffer?
NICE: Neutralisation, ICE table, Check End product
Write out the neutralisation reaction between the reagents
ICE table. Deduct conc./amt/vol. of the limiting reagent.
Check End Product: Ignore water as an end product.
If the remaining two reagents differ from each other by 1 H+ ion, it is a buffer.
Planning (P2 + P3)
Kinetics Experiment. How to outline the determination of changing conc. on the rate of the reaction. [4]
Draw table for 4 experiments, including the volumes of all the reagents + water (to maintain constant total volume), leaving the columns for time and 1/t blank.
Repeat the experiment by stirring __ solution with the volume of ___, ___, ___ and water as indicated in the table above.
Stop the stopwatch when the first ppt appears and determine 1/t.
Why was the ratio of 1-chloropropane : 2-chloropropane found to be 1:1 and not 3:1 as per deduction based off number of hydrogen groups attached?
The formation of 2-chloropropane involves a secondary radical which contains 2 electron donating alkyl groups, whereas the formation of 1-chloropropane involves a primary radical which contains only 1 electron-donating group.
Since the presence of more electron-donating alkyl groups will stabilise the secondary electron deficient radical more than the primary radical. Hence the formation of 2-chloropropane is more favoured.
