Edexcel CHEMISTRY DOUBTS!!!!

[Malak]

Enthalphy change of reaction = reactants - products.

Therefore, (propanoic acid + Hydrogen) - Propanal
              (-1527)+(-286) - (-1821)

Enthalphy change of reaction = +8 kjmol^-1

Oh k thx..
By the way..Can we also use the cycle for this?

[Amelia]

Oh k thx..
By the way..Can we also use the cycle for this?

yes, the Hess's Law. Bonds broken - Bonds formed.

[Uchia]

please help me in those questions

Using IR spectroscopy, the progress of the oxidation of a primary alcohol by aqueous
acidified potassium dichromate could be followed by the change in the height of the
peak due to:

A) O–H 
B) C–H
C) C–C
D) C=O

The peak due to the hydrogen nuclei in the CH2 group in the high-resolution NMR
spectrum of propanal, CH3CH2CHO, is split into which of the following number of peaks?

A)3
B)4
C)5
D)6

When a water molecule absorbs microwaves:
A there is an increase in O–H bond stretching
B there is an increase in O–H bond bending
C there is an increase in the rotation of the H2O molecule
D an O–H bond breaks

[Uchia]

Also this one

The number of peaks in the low-resolution NMR spectrum of
pentan-3-one, CH3CH2COCH2CH3 is:

A 1
B 2
C 3
D 4

[Deadly_king]

Also this one

The number of peaks in the low-resolution NMR spectrum of
pentan-3-one, CH3CH2COCH2CH3 is:

A 1
B 2
C 3
D 4

In low resolution NMR, peaks are formed according to the different hydrogen environment the molecule has.

In this case the answer is 2 because pent-3-one has only two H atoms in different environment namely CH₃ and CH₂.

For more details, click here.

[Uchia]

I think your answer is wrong cz according to the link you gave me it is shown that

CH3CH2COOCH3

it is said that CH3 is an environment
CH2 is one

COO nothing

and CH3 is another one

similarly in pentan-3-one  CH3CH2COCH2CH3

I think it should be 4 right or wrong

[Uchia]

yeah yeah right sorry my mistake

I understood it now

thnxs anyways for your help

[Deadly_king]

I think your answer is wrong cz according to the link you gave me it is shown that

CH3CH2COOCH3

it is said that CH3 is an environment
CH2 is one

COO nothing

and CH3 is another one

similarly in pentan-3-one  CH3CH2COCH2CH3

I think it should be 4 right or wrong

Nan.........the link only gives an example on how you read an NMR spectra.

yeah yeah right sorry my mistake

I understood it now

thnxs anyways for your help

Glad you did

[Amelia]

please help me in those questions

Using IR spectroscopy, the progress of the oxidation of a primary alcohol by aqueous
acidified potassium dichromate could be followed by the change in the height of the
peak due to:

A) O–H 
B) C–H
C) C–C
D) C=O

Primary alcohol oxidises and forms, aldehydes and (further oxidation) acids.
Ans is D.

The peak due to the hydrogen nuclei in the CH2 group in the high-resolution NMR
spectrum of propanal, CH3CH2CHO, is split into which of the following number of peaks?

A)3
B)4
C)5
D)6

Ans is B

 - http://chem242.wikispaces.com/Deepak+Singh's+analysis+of+the+H-NMR+of+propanal

When a water molecule absorbs microwaves:
A there is an increase in O–H bond stretching
B there is an increase in O–H bond bending
C there is an increase in the rotation of the H2O molecule
D an O–H bond breaks

Microwaves contain small amount of energy, the water molecules keep on rotating.
 - http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/-324719c1f8

[Malak]

What is a trace product?

[Uchia]

thanks a lot Amelia you were such a great help I owe you one

[Amelia]

What is a trace product?

Trace Element(s) :- A chemical element required in minute quantities by an organism to maintain proper physical functioning.

thanks a lot Amelia you were such a great help I owe you one

You are welcome.

[Uchia]

hey Amelia are you doing chem A2 this jan

[Amelia]

hey Amelia are you doing chem A2 this jan

I did my As and A2 last june.

[Uchia]

cool I just did AS last june and it was pretty easy