Chemistry: Post your doubts here!

[Casablanca]

How is a temporary/induced dipole involved in (CH3)2CHCH3 (2 methylpropane)?

 

[littlecloud11]

Haha, yes.

http://www.scribd.com/doc/37574186/9701-w01-qp-2
Nov 01, Q4 (c) (i) & (ii) and part (d)

What are the answers?

4ci) we dnt have concentration calculation using pH in our syllabus.

ii) under alkaline conditions H+ reacts with the alkali and so the the ammonium ion reacts with more O2 to make up for the loss in H+ and increase it's conc. thus more products are formed, increasing the chances of the reaction reaching completion.

d) In water-logged conditions there is an absence of O2 in the soil and both the 2nd and the 3rd stage requires a supple of O2. so they don't occur under water-logged conditions.

 

[leosco1995]

4ci) we dnt have concentration calculation using pH in our syllabus.

ii) under alkaline conditions H+ reacts with the alkali and so the the ammonium ion reacts with more O2 to make up for the loss in H+ and increase it's conc. thus more products are formed, increasing the chances of the reaction reaching completion.

d) In water-logged conditions there is an absence of O2 in the soil and both the 2nd and the 3rd stage requires a supple of O2. so they don't occur under water-logged conditions.

Awesome. Thank you so much. ^^

 

[littlecloud11]

Awesome. Thank you so much. ^^

Again, No problem.

 

[shan5674]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_21.pdf 5b(ii) can someone please draw the structural formula of the compound for me i dont understand the skeletal :/

 

[JulyMei]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_21.pdf 5b(ii) can someone please draw the structural formula of the compound for me i dont understand the skeletal :/

is this how it suppose to be?

 

[DragonCub]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_21.pdf 5b(ii) can someone please draw the structural formula of the compound for me i dont understand the skeletal :/

Reacted with Cr2O7(2-) under reflux, the destination shall be carboxylic acid. Any hydroxyl (-OH) and aldehyde (-CHO) groups will be converted into carboxylic acid groups (-CO2H). So the final product should be ethan-di-oic acid, HO2CCO2H or (CO2H)2.
Skeletal formula represent carbon atoms with dots and bonds with lines. Hydrogen atoms which directly connects to carbon are ignored (along with the C-H bonds). All the functional groups (include C=C) must be shown.
this is the skeletal formula for ethan-di-oic acid.

 

[RGBM211]

mmm
1)whats the advantage and disadavatages of fuel cells compared to combustion of hydrogen fuels ?

2)how reaction of esterification is carried out in a laboratory/school?

3)Eutrophication?

yea thats all

Anyone ?

 

[Goku]

A huge favour please?
Im giving two papers tomm InshaAllah and I dont have enough time,so im only preparing for AS P2 , Can anyone give me some tips for A2 P5 ??
anything I should go over or sth?
Please and thankyou!!!

 

[Goku]

mmm
1)whats the advantage and disadavatages of fuel cells compared to combustion of hydrogen fuels ?

2)how reaction of esterification is carried out in a laboratory/school?

3)Eutrophication?

yea thats all

Anyone ?

when water acquires a high concentration of nutrients especially phosphates and nitrates. These promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Which is..bad,duh.

 

[RGBM211]

when water acquires a high concentration of nutrients especially phosphates and nitrates. These promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Which is..bad,duh.

is this enuf for 3-4 marks ?

 

[JulyMei]

mmm
2)how reaction of esterification is carried out in a laboratory/school?

by adding concentrated H2SO4

 

[JulyMei]

is this enuf for 3-4 marks ?

i remembered one of the mark scheme, if u state "eutrophication", u can get 2 marks already.

 

[DragonCub]

mmm
1)whats the advantage and disadavatages of fuel cells compared to combustion of hydrogen fuels ?

2)how reaction of esterification is carried out in a laboratory/school?

3)Eutrophication?

yea thats all

Anyone ?

(1) Advantages are -no pollution -high efficiency
Disadvantages are -high cost & maintenance cost -difficulty of storage (since hydrogen and oxygen need to be liquid for massive storage)
(2) Material: acid & alcohol
Condition: concentrated sulphuric acid & heat
(3)Eutrophication refers to where high-nutrition wastes are dumped into water so that certain plants can become rampant under water. The result is the depletion of oxygen in water and subsequent death of fish etc.

 

[Goku]

is this enuf for 3-4 marks ?

3 marks? yes easily and would pass for 4 too.

 

[RGBM211]

(1) Advantages are -no pollution -high efficiency
Disadvantages are -high cost & maintenance cost -difficulty of storage (since hydrogen and oxygen need to be liquid for massive storage)
(2) Material: acid & alcohol
Condition: concentrated sulphuric acid & heat
(3)Eutrophication refers to where high-nutrition wastes are dumped into water so that certain plants can become rampant under water. The result is the depletion of oxygen in water and subsequent death of fish etc.

thanks

2)ermm you forgot to mention about heat under reflux and mmm the quantities taken should be equal

 

[Goku]

A huge favour please?
Im giving two papers tomm InshaAllah and I dont have enough time,so im only preparing for AS P2 , Can anyone give me some tips for A2 P5 ??
anything I should go over or sth?
Please and thankyou!!!

^^ someone please help,im freaking out here :'(

 

[Paradoxical]

A huge favour please?
Im giving two papers tomm InshaAllah and I dont have enough time,so im only preparing for AS P2 , Can anyone give me some tips for A2 P5 ??
anything I should go over or sth?
Please and thankyou!!!

^^ someone please help,im freaking out here :'(

Check out this thread:
http://www.xtremepapers.com/community/threads/chemo-p5-tips.5917/
There's some notes and stuff in it that should prove useful. ^_^

Also, remember that paper 5 counts as 12% of your overall grade and paper 2 is 23%, so you need to make sure you really do your best in papers 2 and 4 as these are the ones that carry the highest weight-age. Hopefully, this way, you'll be able to make up for getting a lower grade in paper 5.

Hope I helped a little.

 

[DragonCub]

thanks

2)ermm you forgot to mention about heat under reflux and mmm the quantities taken should be equal

Is reflux necessary? Well could not remember it clearly.
As long as the materials are mixed and conditions applied, the reaction occurs, yet taking equal amounts can ensure no remaining reactants afterwards I would say.

 

[RGBM211]

Is reflux necessary? Well could not remember it clearly.
As long as the materials are mixed and conditions applied, the reaction occurs, yet taking equal amounts can ensure no remaining reactants afterwards I would say.

kinda its given in markscheme yep without reflux the reaction cnt be carried out i guess its said heat under reflux