Post by: The SMA on May 21, 2010, 12:14:02 pm
on Q2 (d iii) , Q5 (a) and (c)
and on M/J 2004 paper 2
Q3 c ( the whole question c)
and there's something xtra i wanna ask from u guys,
can someone please explain to me what is permanent dipole, induced dipole
and dipole-dipole interactions?
Will really appreciate if someone could help me :)
Post by: unknown 101 on May 21, 2010, 12:57:22 pm
i need help to answer M/J 2005 paper 2
on Q2 (d iii) , Q5 (a) and (c)
and on M/J 2004 paper 2
Q3 c ( the whole question c)
and there's something xtra i wanna ask from u guys,
can someone please explain to me what is permanent dipole, induced dipole
and dipole-dipole interactions?
Will really appreciate if someone could help me :)
from the equation in 2)d) (i) u know that 2 mol of H2S reacts with 3 mol of 02
find the mr of H2S (2 + 32.1 )will give 34.1 multiply by two ( as there are 2 moles ) to get 68.2
and u know that 1 mol = 24dm3 so 3 moles will = 72
so now u have the all the values soo...
if 68.2g of H2S reacts with 72 dm3 of O2
so 8.65g will react with X
cross multiply ( 8.65 x 72 / 68.2 ) = 9.13 dm3
2nd question:
3)c) (i) u know that 1.20 dm3 of NH3 was dissolved so.....
if 1 mole = 24dm3
then X mole = 1.2 dm3
cross multiply (1.2/24 = 0.5 mol )
c) (ii) equation: 2NH3 + H2SO4 -----> (NH4)2SO4
c) (iii) if 2 mol of ammonia is required to nuetralize 1 mol of sulphuric acid so....
from part (i) u know that we have 0.05 mol of ammonia, so to nuetralize it we need ( 0.05/ 2 = 0.025)
so now we have the moles and concentration, rearrange the formula ( mol = vol x conc ) to find the volume
so...
vol = mol/ conc -----> 0.025/0.5= 0.05 dm3, and we need the volume in cm3, so multiply by 1000
(0.05 x 1000 = 50cm3) so 50 cm3 is required to nuetralize 200 cm3 of aqueous ammonia
permanent dipole : is when you have a polar molecule with oppositely charged ends, and these ends attract other polar molecules, bonding them together. The polar molecules will always be slightly negative on one end and slightly positive on the other.
induced dipole: A dipole-induced dipole attraction is a weak attraction that results when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species.
OR SIMPLY: when a non-polar molecule has it's electron density shifted by a charged molecule, i.e., if a positively charged species is brought near a species with an evenly distributed charge, the electrons go towards the side where the positive species is, and away from the opposite side, creating an artificial dipole
dipole-dipole interaction: this is just the weak van der waal's forces of attraction
hope this helped ;)
Post by: [Spy] on May 21, 2010, 02:15:10 pm
Post by: unknown 101 on May 21, 2010, 02:33:39 pm
thats how we roll nashat ;)
hahhahaha ;)
Post by: The SMA on May 21, 2010, 02:42:01 pm
Post by: unknown 101 on May 21, 2010, 05:40:03 pm
Many many thanks unknown 101 for enlightening all my doubts. Reaaaaaly Appreciate it :) :)
anytime! ;)
Post by: The SMA on May 24, 2010, 11:19:32 pm
Q 2 (a) (d)
Q 3 (b ii) can u please show me how to do the cycle for this please?
Thanks!
Post by: unknown 101 on May 25, 2010, 12:18:58 am
Guys need some help in answering Chemistry Paper2 O/N 2005
Q 2 (a) (d)
Q 3 (b ii) can u please show me how to do the cycle for this please?
Thanks!
hope this helped... :)
but for question 3 b) ii) i dont get wat u mean!!!???
Post by: The SMA on May 25, 2010, 10:50:37 am
oh n i what i meant for the cycle was for Q2 which you already did, sorry for the mistake.
I just want the explainnation on how to answer the Q3 (b ii).
Post by: unknown 101 on May 25, 2010, 01:20:54 pm
Thank you very much for the scan, it is very helpful! i finally understand now :)
oh n i what i meant for the cycle was for Q2 which you already did, sorry for the mistake.
I just want the explainnation on how to answer the Q3 (b ii).
anytime ;)
ok so for Q.3)b)ii), ur are suppose to answer it based on ur knowledge of fertilisers from O LEVEL BIOLOGY !!! :S
so from what i know:
if excess ammonium nitrate gets washed into a stream or river, it will cause the water plants to grow uncontrolabley ( eutrophication ), causing them to block sun light entering the river, causing many underwater plants to die ( no photosynethesis ). Furthermore it causes the plants to use all its resources ( food ) for growth and so the plant eventually dies as there is no resources left! this causes the decomposers to act on the dead plants, which requires oxygen, soo its being used up, so other water animals dont have enough oxygen to survive and they die.
hope this helped :)
Post by: The SMA on May 29, 2010, 07:48:23 am
1) O/N 2004 p2, Q1d (i) (ii), Q 2b, Q 4f (ii)
2) O/N 2008 p2, Q2 (ii),
Post by: The SMA on May 29, 2010, 12:57:43 pm
Post by: aldehyde1612 on May 29, 2010, 01:30:45 pm
Post by: The SMA on May 29, 2010, 02:28:27 pm
for 2008 Q2... which part ii...?
sorry forgot to state it supposed to be Q2 C (ii).
Post by: nid404 on May 30, 2010, 07:45:53 am
guys i need help on answering On
1) O/N 2004 p2, Q1d (i) (ii), Q 2b, Q 4f (ii)
2) O/N 2008 p2, Q2 (ii)
1) nov 04
1) d)i)
ii) bond energy
HI=299kj/mol
H2=436kj/mol
I2=151kj/mol
Energy for bond breaking= 2 X energy to break HI bond= 2X 299=598 kj
Energy for bond making = bond energy of H2 + bond energy of I2= 436+151=587kj
2) b) i) Al2O3 has a high melting point because it's an ionic structure held together by strong electrostatic forces of attraction between oppositely charged ions of Al3+ and O2-
ii) SO3 consists of small molecules held together by weak Van der Waals forces. Hence low mp
ii) SiO2 is a giant covalent molecule. it has strong covalent bonds and requires high energy to break them. P4O10 is a simple molecular compound with weak Van Der Waals forces between the molecules.
4) f) ii) apparently a mistake in the ms :/ Very rarely happens but it is definitely a mistake...I've asked my teachers abt it
structure is
H H
| |
R-C-C -CH2OCOCH3
| |
CH3 Br
Post by: nid404 on May 30, 2010, 07:57:39 am
guys i need help on answering On
2) O/N 2008 p2, Q2 (ii),
2c)ii)
C+ O2--->CO2 -395kj/mol
H2+ 1/2 O2--->H2O -286kj/mol
CH2=C=O + 2O2---> 2CO2+ H2O -1028kj/mol
the reaction's whose enthalpy we want is a combination of the reactions above...figure using hess' law
2C+ H2+ 1/2 O2---> C2H2O
Post by: TJ-56 on May 30, 2010, 08:44:08 am
H H
| |
R-C-C -CH2OCOCH3
|
CH3
[/quote]
hey, i had the same question but where did the c=c go , is it still there and isnt there supposed to be another hydrogen atom on the 2nd carbon from the left?
Post by: nid404 on May 30, 2010, 08:52:21 am
HBr adds across the double bond. It's an addition reaction
Post by: TJ-56 on May 30, 2010, 09:01:46 am
i modified my post.
HBr adds across the double bond. It's an addition reaction
ok sorry didnt notice that.. thanx for the help anyways!
Post by: TJ-56 on May 30, 2010, 09:08:42 am
Post by: girl_92 on May 30, 2010, 11:54:32 am
Post by: Meticulous on May 30, 2010, 12:02:14 pm
Post by: girl_92 on May 30, 2010, 12:42:24 pm
CH3CH2CH=CHCH2CH2OH
ND THE ANSWER IS CH3CH2COOH AND HOOCCH2COOH
HOW DO YU GET THIS
Post by: girl_92 on May 30, 2010, 12:43:54 pm
Post by: highly_ambitious on May 30, 2010, 12:52:36 pm
shall i do all the past papers again or revise ?? plz help!!
Post by: ruby92 on May 30, 2010, 02:49:42 pm
4 b iii ??? ???
Post by: moon on May 30, 2010, 04:43:30 pm
Post by: TJ-56 on May 30, 2010, 05:07:15 pm
where did the carbon atom in the middle go??
Thanks for any help
Post by: sweetie on May 30, 2010, 07:04:59 pm
please can someone confirm if its an error made in the mark scheme about mj 06 q4 (f) (ii)
where did the carbon atom in the middle go??
Thanks for any help
i have da same Q., plzzzzzzzzzzzzz sum1 help
Post by: yinyang on May 31, 2010, 08:13:19 am
please can someone confirm if its an error made in the mark scheme about mj 06 q4 (f) (ii)
where did the carbon atom in the middle go??
Thanks for any help
the formula of the allyl alcohol is CH2=CHCH2OH
when this allyl alcohol is heated under reflux with acidified MnO4- the double bond breaks
so you will have CH2O and COHCH2OH
since it is heated under reflux the products are further oxidised
CH2O -------> 2CO2 + 2H2O
COHCH2OH --------> HO2CCO2H
Post by: superduper2009 on May 31, 2010, 08:38:27 am
Post by: sweetie on May 31, 2010, 09:32:51 am
Post by: superduper2009 on May 31, 2010, 11:40:32 am