Chemistry: Post your doubts here!

[hellangel1]

http://www.chemguide.co.uk/analysis/nmr/highres.html
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/nmr/nmr1.htm

Thank you

 

[Haya Ahmed]

look at this

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_23.pdf

Q2 d (ii) .. why the answer is Positive not negative ??

 

[♣♠ Magnanimous ♣♠]

Thank you

 

[A star]

It is in our course? haha didn't knew until today!

not directly that why i asked him if it was from past papers. You just use it to form compunds after electrophylic addition reactions :3

 

[♣♠ Magnanimous ♣♠]

well my signature is awesome like yours.

not directly that why i asked him if it was from past papers. You just use it to form compunds after electrophylic addition reactions :3

 

[A star]

Yes in a sense you can, however the better reason will be that C does not have empty D orbitals. just remember this one line statement it won't kill you



This my friend is indeed a good question. I would like to know the answer to this as well.. lol How can we determine the Ea? does endothermic reaction show high Ea reactions? or is it the magnitude? no clue.

I think the answer to this comes from the fact that reaction 1 needs to be heated to a higher temperature.. yaar wo AS wala jo tha.. Boltzman Temeperature wala # of particles/energy graph. Increasing temperature increases the number of particles with enough activation energy.

second part you lost me on I think

 

[MiniSacBall]

Color changes from --- to ---- when adding aldehyde to

1. Fehling's Solution
2. Tollens Reagent

Help me!

 

[robinhoodmustafa]

look at this

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_23.pdf

Q2 d (ii) .. why the answer is Positive not negative ??

i think they didnt ask for 'sign' usually they ask to calculate enthalpy change and give its sign along with it.

 

[♣♠ Magnanimous ♣♠]

Color changes from --- to ---- when adding aldehyde to

1. Fehling's Solution
2. Tollens Reagent

Help me!

1. blue to orange red
and 2. colorless to silver mirror type.

 

[robinhoodmustafa]

Color changes from --- to ---- when adding aldehyde to

1. Fehling's Solution
2. Tollens Reagent

Help me!

Blue to Orange

and in Tollens : Colorless to Silver Mirror

 

[♣♠ Magnanimous ♣♠]

Blue to Orange

and in Tollens : Colorless to Silver Mirror

i gave the answer .

 

[robinhoodmustafa]

1. blue to orange red
and 2. colorless to silver mirror type.

What is the color change of ketone in Iodoform test?

 

[robinhoodmustafa]

i gave the answer .

LoL. Its really feels like a race or a competition

 

[zackle09]

Oh this question has given me a lot of trouble lately.

I went with (21/1)*(1/9) = 21/9 = 7/3


My explanation was something like 21/1 = ratio of rate of tertiary to primary H. 1/9 = ratio of tertiary to primary H present. Ratio of J/K = 21/1 * 1/9 = 21/9 = 7/3

J= Tertiary Hydrogen replaced.
K= Primary Hydrogen replaced.

ohhhh! thankyouuuu so muchh!

 

[Haya Ahmed]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_23.pdf

Q2 d (ii) .. why the answer is Positive not negative ??

robinhoodmustafa are you confident with your answer ?! >.> .. I think It is not the reason :|

 

[robinhoodmustafa]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_23.pdf

Q2 d (ii) .. why the answer is Positive not negative ??

robinhoodmustafa are you confident with your answer ?! >.> .. I think It is not the reason :|

If they meant to give a positive sign than they really show it in Ms. That is the only possible reason because we all know Combustion of Hydrocarbon is exo

 

[Haya Ahmed]

So is it wrong If we showed - sign ? robinhoodmustafa

 

[syed1995]

not directly that why i asked him if it was from past papers. You just use it to form compunds after electrophylic addition reactions :3

lol i still have no clue

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_23.pdf

Q2 d (ii) .. why the answer is Positive not negative ??

"to calculate the energy produced by the"

You just need to calculate the energy produced in Joules. And Energy itself is a scalar quantity so cannot be negative. You don't have to state the enthalpy over here. And enthalpy has the +/- sign to it to show whether the energy was produced or used up.

Since they have already told you that energy is produced and you need to calculate the amount of energy produced. The Sign doesn't matter only the magnitude does..

Even if you wrote -XX kJ I don't think you'd have been penalised for that. because sign doesn't matter in this question.

 

[syed1995]

So is it wrong If we showed - sign ? robinhoodmustafa

No. you won't be penalised for that in my opinion. If they specifically show the sign in MS or asked for Enthalpy change, then only the sign matters.. so you're good either way.

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_21.pdf
Q5 b i)

Is my answer correct especially the optical isomer one