Help in AS Chemistry!

[The SMA]

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

[unknown 101]

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

[[Spy]]

thats how we roll nashat

[unknown 101]

thats how we roll nashat

hahhahaha

[The SMA]

Many many thanks unknown 101 for enlightening all my doubts. Reaaaaaly Appreciate it

[unknown 101]

Many many thanks unknown 101 for enlightening all my doubts. Reaaaaaly Appreciate it

anytime!

[The SMA]

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!

[unknown 101]

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!!!???

[The SMA]

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).

[unknown 101]

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

[The SMA]

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),

[The SMA]

could someone help me pleaase?

[aldehyde1612]

for 2008 Q2... which part ii...?

[The SMA]

for 2008 Q2... which part ii...?

sorry forgot to state it supposed to be Q2 C (ii).

[nid404]

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