Chemistry: Post your doubts here!

[Farez]

Thank You so much! But once I made a similar diagram and my teacher pointed out that this is close to electrolysis, draw it as it is in marking scheme

Teachers usually treat the mark scheme as the Bible or something lol. No need to draw it exactly as the mark scheme. Just make sure your diagram includes the relevant points quoted in the mark scheme, as those are what was marked :

• power supply
• electrolyte + filter paper
• buffer
• acid mixture central

So this diagram should suffice:

 

[unique111]

Does anyone have the 'Example Candidate Response Booklet' for chem?

 

[itallion stallion]

Can someone plz explain this
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w13_qp_43.pdf
Question no 6 part F.thanks!

 

[A star]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s13_qp_41.pdf Q2a(iv)

 

[Farez]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s13_qp_41.pdf Q2a(iv)

1. Pick a point on one of the graphs
2. Draw a tangent line and calculate the gradient of that line. This is the rate.
3. Take the appropriate concentrations and place the values of the rate and concentrations in the rate equation
4. Solve for k.

 

[A star]

1. Pick a point on one of the graphs
2. Draw a tangent line and calculate the gradient of that line. This is the rate.
3. Take the appropriate concentrations and place the values of the rate and concentrations in the rate equation
4. Solve for k.

thanks alot budy (Y) .

 

[LeoMessi]

Hahahh. This is one of my better drawings

Always sucked at drawings and diagrams and always will. This is why I loathe P5. All my diagrams are so funny it's actually amusing lol

Abby can you OR ANYONE plss explain the question to me???? The answer is also attached
plsss
ANSWER

 

[GCE As and a level]

https://www.xtremepapers.com/community/threads/chemistry-p21-gt.33403/

GUYS VOTE HERE ABOUT YOUR EXPECTATIONS FOR CHEMISTRY ''GT'' P21
________________________________________________________________________
https://www.xtremepapers.com/community/threads/biology-9700-p11-gt.33482/

GUYS VOTE HERE ABOUT YOUR EXPECTATIONS FOR BIOLOGY ''GT'' P11
________________________________________________________________________

BEST OF LUCK

 

[A star]

https://www.xtremepapers.com/community/threads/new-format-of-exams-for-2014.33380/page-2#post-773505

 

[Dexterwarrior12]

2 Questions. Firstly, in p4 (A2), do we have to memorize the colour of complexes of all transition metals? Apart from Co and Fe ones ofcourse.
Secondly, what about when we add KMno4 to Fe2+ solution? TEchnically, shouldn't the solution turn from green to brown? Mark scheme says that the solution turns colourless and then finally on excess of MnO4- it turns pink. How?

 

[Farez]

Abby can you OR ANYONE plss explain the question to me???? The answer is also attached
plsss View attachment 41708
ANSWER View attachment 41708View attachment 41709

Have you read the chapter on partition coefficients? This page does a great job in explaining the concept and how to do the calculations. http://www.chemguide.co.uk/CIE/section112/learningf.html

Read that page and try to figure out how to solve the question yourself. It's mostly math anyway.

2 Questions. Firstly, in p4 (A2), do we have to memorize the
of complexes of all transition metals? Apart from Co and Fe ones ofcourse.
Secondly, what about when we add KMno4 to Fe2+ solution? TEchnically, shouldn't the solution turn from green to brown? Mark scheme says that the solution turns colourless and then finally on excess of MnO4- it turns pink. How?

No need to memorize colours of complexes, other than Cu2+ complexes, and iron (ii)/(iii) ones. Make sure you know the reason behind the colours as that is a very common question.

As for your second question, it's rather subjective. The colour of the Fe2+ solution really depends on the concentration of the ions. If it's dilute, the colour would be harder to notice than the very prominent purple of the KMnO4 solution. This is what I think to make the most sense. I have no idea what the examiner had in mind lol.

 

[Someone2]

can anyone explain if cyclohexane reacts with NaOH or not?? so confused...

 

[Farez]

can anyone explain if cyclohexane reacts with NaOH or not?? so confused...

Cyclohexane is an unsaturated organic compound so it wouldn't react with NaOH.

Phenol does react with NaOH, as phenol is acidic (lone pair of O being delocalised into the ring causes the O-H bond to be more polar so the H breaks off more easily)

 

[Shkrrhmt]

can teach me steps to sketch graph for acid-base neutralisation? for eg: 25 cm^3 of 0.200moldm^-3 NaOH is titrated against 0.100 moldm^-3 ethanoic acid solution. Tq

 

[Farez]

can teach me steps to sketch graph for acid-base neutralisation? for eg: 25 cm^3 of 0.200moldm^-3 NaOH is titrated against 0.100 moldm^-3 ethanoic acid solution. Tq

This page does a great job in thoroughly explaining it http://www.chemguide.co.uk/physical/acidbaseeqia/phcurves.html

Make sure you understand acid-base reactions, pH calculations, and buffer solutions first though.

 

[AnujaK]

Hi everyone
I've started a site which will provide you with solved papers showing all the steps in the working and with useful tips on the side. The best part is that when you look at a solved paper, you can look at commonly made mistakes and learn from them.
Please do check it out!
https://sites.google.com/site/fromatoscom/home

 

[A star]

can anyone explain if cyclohexane reacts with NaOH or not?? so confused...

NaOH doesnt react with cyclohexane nor cyclohexene it reacts with phenols forming sodium phenoxide

 

[Dexterwarrior12]

Have you read the chapter on partition coefficients? This page does a great job in explaining the concept and how to do the calculations. http://www.chemguide.co.uk/CIE/section112/learningf.html

Read that page and try to figure out how to solve the question yourself. It's mostly math anyway.



No need to memorize colours of complexes, other than Cu2+ complexes, and iron (ii)/(iii) ones. Make sure you know the reason behind the colours as that is a very common question.

As for your second question, it's rather subjective. The colour of the Fe2+ solution really depends on the concentration of the ions. If it's dilute, the colour would be harder to notice than the very prominent purple of the KMnO4 solution. This is what I think to make the most sense. I have no idea what the examiner had in mind lol.

thanks man, thanks alot

 

[A star]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_41.pdf 5d(i)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_ms_41.pdf is the answer correct , i mean is the water molecule sttracted towards Na in this way???

 

[Dexterwarrior12]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_qp_41.pdf 5d(i)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w13_ms_41.pdf is the answer correct , i mean is the water molecule sttracted towards Na in this way???

I found that confusing too, but I don't think its important, because they gave marks without the mention of that point too, anyways, hoping that someone will answer it here,