Physics, Chemistry and Biology: Post your doubts here!

[Nita Mahajan]

Help with chemistry problem?
4.2 g of cerium reacted with oxygen to form 5.16 g of an oxide of cerium. Complete the following to determine the formula of this oxide.
(a) Number of moles of cerium atoms used
(b) Mass of oxygen that reacted
(c) Number of moles of oxygen atoms in oxide
(d) Ratio by moles of cerium atoms to oxygen atoms
(e) Formula of this oxide of cerium is ………

if the equation is given, then the problem could be solved easily. Is there any equation given of the reaction?

 

[Nita Mahajan]

can someone explain what are eddy currents?

 

[examkiller]

Really mixed up with polymerisation ( polyester and polyamide ) . Do we need to learn the linkages , is the amide linkage c=o n-h ? how to apply it on pastpapers ?
How to remove the parts of the condensation polyester and polyamide ? What is a Diamene ? how can you draw tetrafluoroethene ? and the pastpapers on mole questions are very different than theory of moles. And are metals are reduced or oxidised, how can you find out which starts first. red or oxi ?

 

[sara fayed]

it is not working dude please i need it urgent

 

[sara fayed]

it is not working dude please i need it urgent

 

[rowiid]

The quality and quantity of food available worldwide has been improved by artificial
selection (selective breeding) and genetic engineering.
(d) Use a named example to outline how artificial selection is used to improve the quantity
or quality of food.

 

[Freddie105]

I need to find exercise for genetic chapter

 

[SIstudy]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s08_qp_1.pdf

Q9
Ps can some one help

 

[Afzal1]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s08_qp_1.pdf

Q9
Ps can some one help

Its quite easy u need to know the no of electrons needed/lost by each atom to become stable
P requires 2 electrons and Q needs to lose 1 electron
So P : Q
2 : 1
CROSS THEM OVER so the answer is PQ2

 

[SIstudy]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_1.pdf

Q16 & 31
any1 help pls :/

 

[SIstudy]

T

Its quite easy u need to know the no of electrons needed/lost by each atom to become stable
P requires 2 electrons and Q needs to lose 1 electron
So P : Q
2 : 1
CROSS THEM OVER so the answer is PQ2

Thankx fr ur help

 

[Nita Mahajan]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_1.pdf

Q16 & 31
any1 help pls :/

Q 16-Copper oxide will be reduced because it is loosing oxygen and becoming copper. Gax X is Carbon monoxide
Q31- Answer is D. You should know that NO2 and SO2 are two gases that cause acid rain.

 

[Afzal1]

T

Thankx fr ur help

Ahhhh..... its no problem you are most welcome for any doubts any clarifications

 

[inquisitiveness]

hm guys..can someone please explain me the earthing thing related to induced spheres.
When do the electrons escape TO earth from sphere and when do they MOVE UP FROM earth to sphere?(Physics)

 

[Afzal1]

hm guys..can someone please explain me the earthing thing related to induced spheres.
When do the electrons escape TO earth from sphere and when do they MOVE UP FROM earth to sphere?(Physics)

see this website http://www.physicsclassroom.com/Class/estatics/u8l2b.cfm

 

[arsenal4ever]

Have you guys finish every subjects in your school?

Mine, Bio : Only inheritance and DNA left
Physics: Done everything
Chemistry: Polymers...

 

[Afzal1]

Have you guys finish every subjects in your school?

Mine, Bio : Only inheritance and DNA left
Physics: Done everything
Chemistry: Polymers...

Maaaan...... i guess ur very late in our skool all the subjects have been completed +revision twice

 

[arsenal4ever]

Maaaan...... i guess ur very late in our skool all the subjects have been completed +revision twice

I know, still having Easter holiday right now, for 2 weeks. The teachers are quite slow.. Damn.. Which school are you?

 

[nemonoorhan]

how can u study fro biology and get an A** PLEASE HELP ??!?!?!!!?

 

[Iishrak]

can i get an A phy,bio,chem....is it easy...???

i find physics an easy subj to get an a, but chem n bio idonthinkso unless ur super talented