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Chemistry: Post your doubts here!

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Faaiz Haque

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ZaqZainab said:
The general formula for ester is there in the pic It is always suppose to be there in an ester if it isn't then that is not an ester View attachment 37732
So they have given me C5H10O2

CH3-CH2-CH2-CH2-COOH----->C4H9-CO2H

CH3-CH2-CH2-COO-CH3------->C3H7CO2CH3

CH3-CH2-COO-CH2-CH3------>C2H5CO2C2H5

I am just moving the COO group If you notice in the first one the COO group is in the end and then in second one its in the second last place and in the third one its is in the middle You have to draw this with all the Bonds showing
Click to expand...
ty
 
sidbloom1995

sidbloom1995

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yousef said:
When add NaOH with compound with has C=C bond &carboxilic acid ( eg. propenoic acid ).. will it be addition / condensation
and do we consider NaOH as functional group ??
Click to expand...
i dont know of a reaction between >C=C< with NaOH but with COO2H the H goes to the -OH of NaOH and form H2O and the becomes CO2-Na+ it will be a dehydration reaction!
and no NaOH is not a functional group!! ( i still don get why you said that but so far that will be the ans. to it)
 
sidbloom1995

sidbloom1995

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1357911 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_4.pdf
Q-2 a iv?? Can someone please help me??:unsure:
Click to expand...
the question states that it is a dibasic acid, that means that there are two -COOH groups present at it's two ends
you first find the no. of moles of the NaOH, which in this case is 1.2 x 10^-3
then since you know that there are two acidic groups then that mean that we will need 2 molecules of NaOH for 1 molecule of "A"
so we use ratio method to deduce the moles of "A" which will be [1.2 x 10^-3]/2 = 6 x 10^-4
now you have the moles and the question have given you the mass of 0.1g so use that to get the Mr., [0.1]/[6 x 10^-4] = 166.6 which we will round off to 166
we already now that we have 2[-COOH] so that is a must add and it's Mr. is 90! (you can calculate that)
subtract 90 from 166 and you will get 76!
that means that your rest of the mass of C and H should add up to 76
in this case we will have 3C and 4H to add up to 76 so that will be the rest of your structure, giving you some thing like this: HOOC-C6H4--COOH
 
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Snowysangel

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And in this too:
Which element of the 3rd period requires the least number if moles of oxygen for the complete combustion of 1 mil of the element?
A) aluminum
B) magnesium
C) phosphorus
D) sodium
 
daredevil

daredevil

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Snowysangel said:
And in this too:
Which element of the 3rd period requires the least number if moles of oxygen for the complete combustion of 1 mil of the element?
A) aluminum
B) magnesium
C) phosphorus
D) sodium
Click to expand...

3/2O2 + Al -->Al2O3

Mg + O --> MgO

P + 5/4O2 ---> 1/4P4O10

Na + 1/2O2 --> 1/2Na2O


so i guess sodium is the answer :)
 
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