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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 253813 times)

Offline Assi1993

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #900 on: April 20, 2011, 11:30:29 pm »
hello all!
this is a question from january 2011 chem unit 5!

2 Which of these four amino acids could NOTTT rotate the plane of plane-polarised light?
A H2NCH(CH3)COOH
B H2NCH(CH2COOH)COOH
C H2NCH2COOH
D H2NCH(CH2SH)COOH

answer is C

I know that chiral carbon causes the rotation
but im confused about how do we know that which 1 has chiral centre and which doesnt :(

waiting for reply!-_-
« Last Edit: April 20, 2011, 11:32:19 pm by Assi1993 »
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Offline HUSH1994

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #901 on: April 21, 2011, 05:20:31 pm »
you can draw a rough shape of the compund and check which has 4 different groups attached to it
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Offline EMO123

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #902 on: April 21, 2011, 05:45:31 pm »
Quote from: Assi1993 on April 20, 2011, 11:30:29 pm
hello all!
this is a question from january 2011 chem unit 5!

2 Which of these four amino acids could NOTTT rotate the plane of plane-polarised light?
A H2NCH(CH3)COOH
B H2NCH(CH2COOH)COOH
C H2NCH2COOH
D H2NCH(CH2SH)COOH

answer is C

I know that chiral carbon causes the rotation
but im confused about how do we know that which 1 has chiral centre and which doesnt :(

waiting for reply!-_-

ya it is C
draw all the structures
so which structure as both pie and sigma bong does not rotate
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Offline Assi1993

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #903 on: April 21, 2011, 09:14:22 pm »
got it =)
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Offline Mike Benn

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #904 on: April 22, 2011, 03:43:06 pm »
hey there....plz can anyone tell me what's the definition for Effective Nuclear Charge...( it should be exact pls . as me got my Unit 2 Exam this May )
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Offline EMO123

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #905 on: April 22, 2011, 04:13:09 pm »
Quote from: Mike Benn on April 22, 2011, 03:43:06 pm
hey there....plz can anyone tell me what's the definition for Effective Nuclear Charge...( it should be exact pls . as me got my Unit 2 Exam this May )
there are three answers i got it think and see which one would you prefer to understand.

1st answer-Effective nuclear charge is the portion of the nuclear charge that is experienced by the highest energy level electrons.
2nd answer-ENC is the charge felt by the valence electrons after you have found the number of shielding electrons that surround the nucleus.
3rd answer-Also known as the kernel charge, ENC is the net positive charge experienced by an electron in a multi-electron atom.
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Offline Mike Benn

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #906 on: April 22, 2011, 04:18:05 pm »
Thankxx Dude..all 3 are worth memorising..:P
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Offline EMO123

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #907 on: April 22, 2011, 04:19:47 pm »
Quote from: Mike Benn on April 22, 2011, 04:18:05 pm
Thankxx Dude..all 3 are worth memorising..:P
it's k anytime
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Offline Aadeez || Zafar

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #908 on: April 24, 2011, 06:15:54 am »
Quote from: Assi1993 on April 20, 2011, 11:30:29 pm
hello all!
this is a question from january 2011 chem unit 5!

2 Which of these four amino acids could NOTTT rotate the plane of plane-polarised light?
A H2NCH(CH3)COOH
B H2NCH(CH2COOH)COOH
C H2NCH2COOH
D H2NCH(CH2SH)COOH

answer is C

I know that chiral carbon causes the rotation
but im confused about how do we know that which 1 has chiral centre and which doesnt :(

waiting for reply!-_-
chiral cntres are the carbon atom attached to four different atom/groups


see this for more help


http://www.khanacademy.org/v/introduction-to-chirality?p=Organic%20Chemistry

http://www.khanacademy.org/v/chiral-examples-1?p=Organic%20Chemistry

http://www.khanacademy.org/v/chiral-examples-2?p=Organic%20Chemistry
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Offline EMO123

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #909 on: April 24, 2011, 06:19:41 am »
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Offline Assi1993

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #910 on: April 24, 2011, 02:30:32 pm »
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Offline Aadeez || Zafar

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #911 on: April 24, 2011, 05:15:30 pm »
Quote from: Assi1993 on April 24, 2011, 02:30:32 pm
thankYou so much!!+ rep:) God bless
thanks man got this aftr long time
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Offline Mike Benn

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #912 on: April 25, 2011, 10:52:07 am »
Hey Guys ..Hi.....acutally i needed something kinda file ( which includes different past papers ) so that i could practisce....any one got it..

Much Appreciated if someone sends it ..
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Offline red_911

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #913 on: April 25, 2011, 03:04:56 pm »
if there are 2 bond pairs n one lone pair what is the angle ?
n if 2 bond n 2 lone pairs ?
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Amelia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #914 on: April 25, 2011, 04:09:53 pm »
Quote from: red_911 on April 25, 2011, 03:04:56 pm
if there are 2 bond pairs n one lone pair what is the angle ?

You mean, three bond pairs and one lone pair...? It's  107.3°.

Quote
n if 2 bond n 2 lone pairs ?

104.4°

You will find a list of molecules, their shapes and angles  Here
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