« previous next »
Pages: 1 ... 18 19 [20] 21 22 ... 116   Go Down

Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 253846 times)

Offline Meticulous

  • SF Master
  • ******
  • Posts: 2486
  • Reputation: 19401
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #285 on: May 30, 2010, 06:02:58 pm »
Quote from: Sweet_03 on May 30, 2010, 06:01:06 pm
but i find the old paper 2 questions easier =/
+ for unit 2 .. is the question only from the old paper 2 ? or is it even from the old paper 1 ?

Paper 1 and 2
Logged

Offline Igcseboy

  • SF Citizen
  • ***
  • Posts: 183
  • Reputation: 191
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #286 on: May 30, 2010, 06:06:18 pm »
Quote from: kim on May 30, 2010, 06:00:38 pm
well the only proof u can get is so sum pp the questions come again and again
do u take bio??

nopee
Logged

Offline Kim

  • here comes trouble!=D
  • SF V.I.P
  • ********
  • Posts: 9835
  • Reputation: 36270
  • Gender: Female
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #287 on: May 30, 2010, 06:11:39 pm »
Quote from: Igcseboy on May 30, 2010, 06:06:18 pm
nopee

well then cant give ya proof
Logged
After all is said and done, more is said than done.

By the time a man realizes that maybe his father was right, he usually has a son who thinks he’s wrong.

The early bird may get the worm, but the second mouse gets the cheese.

Offline Igcseboy

  • SF Citizen
  • ***
  • Posts: 183
  • Reputation: 191
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #288 on: May 30, 2010, 06:13:23 pm »
polypropene does not have a sharp melting temperature but softens over a range of temperatures suggest why this is so??
Logged

Offline Igcseboy

  • SF Citizen
  • ***
  • Posts: 183
  • Reputation: 191
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #289 on: May 30, 2010, 06:15:36 pm »
suggest why it is not possible to find the enthalpy of formation of carbon monooxide directlly??
Logged

Offline Meticulous

  • SF Master
  • ******
  • Posts: 2486
  • Reputation: 19401
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #290 on: May 30, 2010, 06:17:24 pm »
Quote from: Igcseboy on May 30, 2010, 06:13:23 pm
polypropene does not have a sharp melting temperature but softens over a range of temperatures suggest why this is so??

Because it is not pure. An impure substance melts or boils over a temperature range.
Logged

Offline Uchia

  • SF Citizen
  • ***
  • Posts: 171
  • Reputation: 379
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #291 on: May 30, 2010, 09:23:38 pm »
this polypropene question is in unit 1
Logged

Offline Saladin

  • The Samurai
  • Honorary Member
  • SF V.I.P
  • *****
  • Posts: 6530
  • Reputation: 59719
  • Gender: Male
  • I believe in those who believe in me
    • Student Tech
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #292 on: May 30, 2010, 09:38:08 pm »
Quote from: ~ A.F ~ on May 30, 2010, 06:17:24 pm
Because it is not pure. An impure substance melts or boils over a temperature range.

That is not true actually, it is because there are many varying chain lengths in the substance. This is the answer in the mark-scheme.
Logged

Offline Blizz_rb93

  • SF Senior Citizen
  • *****
  • Posts: 815
  • Reputation: 1175
  • Gender: Male
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #293 on: May 31, 2010, 02:03:37 pm »
can someone give me summarised notes of unit 2.3 intermolecular forces from the edexcel as chemistry cause i really dont understand much :/

thank you!!
Logged

Offline Saladin

  • The Samurai
  • Honorary Member
  • SF V.I.P
  • *****
  • Posts: 6530
  • Reputation: 59719
  • Gender: Male
  • I believe in those who believe in me
    • Student Tech
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #294 on: May 31, 2010, 02:05:51 pm »
Chemguide is the best place to learn pretty much anything in chemistry.

I would advise you to go there.
Logged

Offline Blizz_rb93

  • SF Senior Citizen
  • *****
  • Posts: 815
  • Reputation: 1175
  • Gender: Male
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #295 on: May 31, 2010, 02:09:53 pm »
Quote from: Engraved on May 31, 2010, 02:05:51 pm
Chemguide is the best place to learn pretty much anything in chemistry.

I would advise you to go there.
okay im checking it out now, thank you! :)
Logged

Offline Sweet_03

  • SF Immigrant
  • **
  • Posts: 55
  • Reputation: 39
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #296 on: May 31, 2010, 03:01:42 pm »
Guys , if you check Unit 1 June 2006 Markscheme ..
the Answer for Question 3 (a)(ii)
it says:
electrons promoted (by heat/flame to a higher level) (1)
NOT electrons excited
fall back down/return (1)
emit light (1)

wait wats [NOT electrons excited] ??
ive always learned it as EXCITED ! isnt thst right ?  ???
Logged

Offline Kim

  • here comes trouble!=D
  • SF V.I.P
  • ********
  • Posts: 9835
  • Reputation: 36270
  • Gender: Female
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #297 on: May 31, 2010, 03:04:33 pm »
Quote from: Sweet_03 on May 31, 2010, 03:01:42 pm
Guys , if you check Unit 1 June 2006 Markscheme ..
the Answer for Question 3 (a)(ii)
it says:
electrons promoted (by heat/flame to a higher level) (1)
NOT electrons excited
fall back down/return (1)
emit light (1)

wait wats [NOT electrons excited] ??
ive always learned it as EXCITED ! isnt thst right ?  ???

wat they want u to write is dat electrons are promoted to higher energy levels by heating
do not write electrons are excited
Logged
After all is said and done, more is said than done.

By the time a man realizes that maybe his father was right, he usually has a son who thinks he’s wrong.

The early bird may get the worm, but the second mouse gets the cheese.

Offline Saladin

  • The Samurai
  • Honorary Member
  • SF V.I.P
  • *****
  • Posts: 6530
  • Reputation: 59719
  • Gender: Male
  • I believe in those who believe in me
    • Student Tech
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #298 on: June 03, 2010, 06:33:45 pm »
The answer to 10a) is A and the answer to 10b) is C. This is what the markscheme says.

But I believe that 10a) should be B.

And 10b) should be D.

But I simply do not get this.
Logged

Offline Meticulous

  • SF Master
  • ******
  • Posts: 2486
  • Reputation: 19401
Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #299 on: June 03, 2010, 07:48:15 pm »
10a)

The forward reaction is exothermic. Therefore, increasing the temperature will counteract this change, shifting to the endothermic side. (Left hand side|). An important point to notice is that when talking about yield, we ALWAYS mean the product. Therefore the yield will decrease.

And we know that increasing the temperature increase the reaction rate.

Therefore the answer is A

Clear?

Logged
Pages: 1 ... 18 19 [20] 21 22 ... 116   Go Up
« previous next »