tests tests and more tests. tmr is the 2nd & last test of the week. *thank god* but this week is not so bad as afterall, tmr is sorta the 'last day of the week' as fri is national day's celeb where sch will end really early. and the upcoming mon is a public holi [: week 8- two weeks from now is gonna be hell with 2 CAs on the same day & 2 A'lvl SPA exams! Oh my god. DX hope that i'll survive that week as it is truly a big one- all the 4 exams, especially SPA which makes up a certain % in the A'lvl grade. for real. :S sigh. somebody told me yesterday that the key to studying is to sleep on your book. sounds nice (: won't be too comfortable though :P haha i truly wish that that will work. not gonna try it though. somebody please prove that it will work and let me know. (: Tmr's chem test is on gaseous state & periodicity. not a very heavy load, but i shall not take it too lightly cuz it's always for chem where im fully prepared that i get sucky results ): i hv no idea why. we'll see tmr. these 2 are probably two of the easiest chapters, and i will have to do well to get back on track before promos in 8 weeks time.Gaseous State5 assumptions for an ideal gas:
1. the particles in a gas are in constant random motion, they collide with each other as well as with the walls of the container.
2. the volume occupied by the gas particles are negligible as compared to the volume occupied by the gas.
3. the forces of attraction between the gas particles are negligible.
4. the collisions of the gas particles with each other as well as with the walls of the container are
perfectly elastic- no energy is lost in the process.
5. the
average kinetic energy of the particles is
directly proportional to the
absolute temperature of the gas (in Kelvins).
Boyles' law: states that at constant temperature, the volume of a given mass is inversely proportional to the applied pressure. PV=constant P1V1=P2V2
Charles' law: states that at constant pressure, the volume of a given mass is directly proportional to its
absolute temperature in Kelvin. V/T = constant V1/T1=V2/T2
Combined gas law: PV/T=constant P1V1/T1 = P2V2/T2
Avogadro's law: states that at constant pressure and temperature, the volume of a gas is directly proportional to the no. of moles of the gas. V/n = constant
The ideal gas equation: PV=nRT
P in Pa, V in m3, T in K, R=8.314 JK-1mol-1
conversion scale: 1atm= 101000 Pa, degree celsius + 273.15= Kelvin,
1 cm3= 10^-3 dm3= 10^-6 m3
PV= mRT/Mr
P= pRT/Mr where p=density g dm^-3
A real gas unlike ideal gas has definite volume, and intermolecular forces are present between gas particles. A real gas deviates most from an ideal gas at high pressure and low temperature.
For 1mole of idel gas, PV/RT=1
At high temperature,
-the molecules are close together. the attractive intermolecular forces becomes significant.
-the attraction will cause the gas particles to be pulled closer together and thus collide with the wall of the container with reduced forces. PV/RT <> 1
At low temperatures,
- the kinetic energies of the particles are low.
- the low KE is insufficient to overcome the intermolecular forces of attraction
during collisions, and hence it becomes not negligible.
Nature of gas
-the greater the no. of electrons in the particles of a gas, the stronger the intermolecular forces,
-the greater the deviation from an ideal gas
behaviour.
Therefore, a real gas approaches an ideal gas behaviour when it has high temprature and low pressure.
Dalton's Law: The total pressure of two or more gases in a mixture, that do not react chemically woth each other, is equal to he sum of partial pressures of the gases in the mixture.
Partial pressure=mole fraction x total pressure
Area under Maxwell-Boltzmann graph=no. of molecules
The distribution of molecular speed depends on the
-
Mass: molecules with lower masses have higher
average speeds
-Temperature: the most probable speed increases. there is an increase in no. of molecules with higher speeds and decrease in no. of molecules with lower speed. the curve is more flattened. however the total are under the graph which represents the
total no. of molecules
present remains the same.
that's about it for gaseous state! (: yay, hope that i will still rmb this later & ofcourse, tmr during the test(: wish i had time to go through periodicity now, but lesson is in abt 11 mins time at 9.30am. :S but i still have a feeling that i will be distracted all day by memorizing during every lecture, & especially the talk thats gonna take up all the whole of my afternoon frm 2.30-5pm ): hope daddy picks me home on time :/ and the thing about taking a nap- idk, yesterday i napped but i was even more tired n i zz at 12 ): i ought to catch my bachelor rome tonight @ 12.30-1.30am. [: n what's with adam's twitter acct ): it's been like ard 21 days since it could work ): common guys, fix the prob and let his account run! no more hackers please. Arrghh. it's sad seeing more & more people [127,082 people till this very moment] following him, with no tweets from him for this long.. ): waiting for his bubble tweet (:
♥ M A D A-bout A D A M | 8:12 AM
