Tips For Chemistry P1

Here we are, approaching the last test for Chemistry AS and also happen to be the most difficult of all the three.

• Refer back to the very first post in this blog. Those tricks are specially useful for the last 10 questions.
• Master your stoichiometry well. I repeat. Master your stoichiometry.
• Standard enthalpy change of formation: it only forms one mole. 2H2+O2-> 2H2O is not one mole. H2+0.5O2->H2O is one mole. (This sentence may contains a lot of grammatical error.)
• Iodine is solid at r.t.p and bromine is liquid at r.t.p

These two structures are two different chemicals. Sorry for the horrible drawing. The point is the position of the -OH group. (Important in chirality)

• C6H5 is a phenyl group and they are nonreactive.
• Either you find the odd one out or find the most correct choice of answer.
• When you see a double bond in an organic compound, do not easily mark it as an alkene. It can be either carboxylic acid/carbonyl (aldehyde and ketone)/ester.
• If the question starts with a general fact, please skip them and go directly to the question. If you do need to read them, please do not treat it like the "Did You Know" section in magazines. This is an exam.
• Haber process is exothermic, in case you forgot.
• Precipitate is still an ion. Yes it is a solid but it doesn't it need to be a pure element?
• Whatever it is, Group I base and alkali is stronger than the Group II base and alkali, provided that they are in the same period.
• Remember all of the bond angle. One method to memorize them is to remember two numbers: 109.5 and 2.5 . Every addition of lone pair, just subtract 109.5 by 2.5 and repeat it for further addition of lone pair.
• All alkane bond angle is roughly 109.5 (degree). Molecules that have a double bond will have a bond angle of 120 (degree). Molecules that have one/two lone pairs follows the trend of either nitrogen/oxygen.
• If the questions have a mathematic calculation (except stoichiometry), unless you are confident with your math. skill, skip them first.
• And again, Group I or II oxides will not dissociate into its element and oxygen gas with only using Bunsen burner.
• Enthalpy change=Bond making-bond breaking
• Pray a lot for this test. I may not be a religious person but at least faith will give us hope. And hope will give us something to cling on to success.