Chemistry: Post your doubts here!

[daredevil]

can u please help me sketch that titration curve q1b(iii)

see u have a weak base at first so pH slightly lower than 7 and a strong base so pH will rise up to almost a full 14 at the end when all is in...

curve and tilt the corners of the graph but u get the idea
and i missed somehting.... the equilibrium point will be marked with an 'x' in the halfway of the vertical line if needed... here it isn't needed i think.
tell me if u dont get this

 

[snowbrood]

see u have a weak base at first so pH slightly lower than 7 and a strong base so pH will rise up to almost a full 14 at the end when all is in...

curve and tilt the corners of the graph but u get the idea
and i missed somehting.... the equilibrium point will be marked with an 'x' in the halfway of the vertical line if needed... here it isn't needed i think.
tell me if u dont get this

i know it should start at 1.94 and end at 14
there should be a vertical line at 10vol added but at what ph should that curve join the vertical line i dont get it and the vertical line should go how much units upwards

 

[daredevil]

i know it should start at 1.94 and end at 14
there should be a vertical line at 10vol added but at what ph should that curve join the vertical line i dont get it and the vertical line should go how much units upwards

it's no hard and fast rule... even the starting point is at 1.94 bcz u calculated it. and u have the equation so u know what ratio of volumes would do the complete reaction but u dont know the pH at which neutralisation is complete so u just have to work with the concept that as it was a weak acid and stronger base, the mid point of the vertical line should be slightly above pH 7 ... and r u sure about the 1.94?? bcz that does not seem like the pH a WEAK acid would have. 1.94 is QUITE acidic.
we only work with the numericals we have and other than that we need to show the right concept and it's done

 

[aaaamfa]

2) In the preparation of soft margarine, glyceryl trieleostearate
is suitably hydrogenated so that, on average, one of its side-chains is converted into the
CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO2 residue and two side-chains are converted into the
CH3(CH2)7CH=CH(CH2)7CO2 residue.
How many moles of hydrogen are required to convert one mole of glyceryl trieleostearate into the
soft margarine?
A 4 B 5 C 6 D 9

need help with the explaination how do we get to the ans in such questions

 

[aaaamfa]

Section A question no. 6 i dont know what to do and how to do

 

[aaaamfa]

section A
question no. 9
question no. 10
question no. 11
Section B
question no. 33

 

[aaaamfa]

^^^^^
srry for posting many questions at a time
but i am preparing for as at home and need a little co-operation frm the ppl of this site

 

[daredevil]

^^^^^
srry for posting many questions at a time
but i am preparing for as at home and need a little co-operation frm the ppl of this site

ummm is D the answer??

 

[snowbrood]

it's no hard and fast rule... even the starting point is at 1.94 bcz u calculated it. and u have the equation so u know what ratio of volumes would do the complete reaction but u dont know the pH at which neutralisation is complete so u just have to work with the concept that as it was a weak acid and stronger base, the mid point of the vertical line should be slightly above pH 7 ... and r u sure about the 1.94?? bcz that does not seem like the pH a WEAK acid would have. 1.94 is QUITE acidic.
we only work with the numericals we have and other than that we need to show the right concept and it's done

i dont kw i think examiner did a blunder here i dont get the graph at all half equavelnce point equavalence point all are against the rules lets see maybe i have to ratafy it well u can check the ms

 

[crys123]

the answer is D. Why is C wrong? C and D both have one chiral centre and they both have -COOH group!

 

[crys123]

Ans is C.

 

[crys123]

the ans is D

 

[crys123]

this paper is absolutely killing me! ans is D

 

[hino]

this paper is absolutely killing me! ans is D

tertiary halogenoalkanes are the ones that only proceed through Sn1 mechanism and Dz the only option which consists of a tertiary halogenoalkane
A and B both are primary ones while C is a secondary one
Just in case if you are unsure about what a tertiary one is :In a tertiary halogenoalkane, the carbon atom holding the halogen is attached directly to three alkyl groups which in this case is (Ch3)3CI

 

[crys123]

tertiary halogenoalkanes are the ones that only proceed through Sn1 mechanism and Dz the only option which consists of a tertiary halogenoalkane
A and B both are primary ones while C is a secondary one
Just in case if you are unsure about what a tertiary one is :In a tertiary halogenoalkane, the carbon atom holding the halogen is attached directly to three alkyl groups which in this case is (Ch3)3CI

ok got it. i thought SN1 mechanism worked for both secondary and tertiary halogenoalkanes. thats why i couldnt understand how both C and D could be right.

 

[Starlight97]

Someone plz give the name for As and A A chemistry book

 

[crys123]

Someone plz give the name for As and A A chemistry book

cambride international AS and A level chemistry coursebook by Roger Norris, Lawrie Ryan and David Acaster. Some people use additional books but this one is pretty much enough for our course.

 

[SIstudy]

Pls help me with these questions
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf Q4, Q5,Q6, Q8
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s09_qp_1.pdf Q33
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_11.pdf Q7

 

[snowbrood]

how to study chemistry of life chapter no 28 of chemistry a2 i just dont get it

 

[selena]

I was doing mcqs from the redspot chemistry Mcqs book and the questions from the 80s & 90s were extremely difficult and they were from p3 p4 mostly. Are they as level questions or a2??