Physics, Chemistry and Biology: Post your doubts here!

[kainat husain]

PLEASE HELP
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w08_qp_1.pdf
q10 the answer is B but balancing is difficult :/ how to do :/
q13 the answer B but how :/
q14 how the answer is D :/
q15 the answer is A
q16 the answer is D
q17 the answer is A
please help

any one :/ :/

 

[fishcook]

An excess of copper oxide is added to the acid, meaning that the salt is added in such quantities that no more of the salt can dissolve in it anymore i.e the acid has become saturated.

im sorry i dont understand

 

[Maz]

any one :/ :/

10) small tip about balancing - always keep the balancing of oxygen and hydrogen for the last.
13) you have to know the electrolysis of molten lead bromide.
14) Since both of them are positive.
15) sorry.
16) Using fuels is always exothermic and hydrogen is oxidised to H2O, uranium only emits radiation which is used, it is not oxidised.

 

[IGSCE.Geek.]

10) small tip about balancing - always keep the balancing of oxygen and hydrogen for the last.
13) you have to know the electrolysis of molten lead bromide.
14) Since both of them are positive.
15) sorry.
16) Using fuels is always exothermic and hydrogen is oxidised to H2O, uranium only emits radiation which is used, it is not oxidised.

and also 17) copper oxide always forms copper after heating
18) the most reactive is never reduced

 

[122]

I guess im late now..u probably finished your exam

hey i am talking abt chemistry not bio . chem is tommorrow

 

[kainat husain]

10) small tip about balancing - always keep the balancing of oxygen and hydrogen for the last.
13) you have to know the electrolysis of molten lead bromide.
14) Since both of them are positive.
15) sorry.
16) Using fuels is always exothermic and hydrogen is oxidised to H2O, uranium only emits radiation which is used, it is not oxidised.

thank uuuu

 

[kainat husain]

and also 17) copper oxide always forms copper after heating
18) the most reactive is never reduced

these answers r for the same paper :/

 

[Maz]

thank uuuu

No problem!

 

[Lost_Life]

Can anyone help me?
An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated
copper(II) sulfate.
The processes listed may be used to obtain crystals of hydrated copper(II) sulfate.
1 concentrate the resulting solution
2 filter
3 heat the crystals
4 wash the crystals
Which processes are needed and in which order?
A 1, 2, 3 and 4
B 1, 2, 4 and 3
C 2, 1, 2 and 3
D 2, 1, 2 and 4
i know that the answer is D because 3 should NOT be involved , but other than that.. could some1 explain?

 

[AAnsarii]

after how many hours will start ur exam

already gave it(bio)

 

[AAnsarii]

Yes D is ryt But energey is not lost by respiration???

energy is lost by respiration, according 2 what i noe, might b wrong

 

[Maz]

Can anyone help me?
An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated
copper(II) sulfate.
The processes listed may be used to obtain crystals of hydrated copper(II) sulfate.
1 concentrate the resulting solution
2 filter
3 heat the crystals
4 wash the crystals
Which processes are needed and in which order?
A 1, 2, 3 and 4
B 1, 2, 4 and 3
C 2, 1, 2 and 3
D 2, 1, 2 and 4
i know that the answer is D because 3 should NOT be involved , but other than that.. could some1 explain?

That itself disqualifies all the other 3 options.
Other than that, (A & B) , why should one concentrate an already saturated solution for crystallization?

 

[AAnsarii]

any one :/ :/

15-when 1000cm3 is increased by 10 deg C, (heat is distributed), so when 500cm3 is added wid d sm amount of X, heat will b conc. on a lesser volume(half d vol), so increase in temp will double

 

[Lost_Life]

15-when 1000cm3 is increased by 10 deg C, (heat is distributed), so when 500cm3 is added wid d sm amount of X, heat will b conc. on a lesser volume(half d vol), so increase in temp will double

YES, THANK YOU!

 

[thats_me]

energy is lost by respiration, according 2 what i noe, might b wrong

So that was wat i said :| wat was wrong thn :S

 

[Lost_Life]

So that was wat i said :| wat was wrong thn :S

its right , by respiration and excretion

 

[Rahma Abdelrahman]

Guys listen to Rahma Abdelrahman she knows best about this whole organ tissue thing

 

[EpicLol]

ppl

Do u think chem paper 1 will be hard??

 

[Lost_Life]

ppl

Do u think chem paper 1 will be hard??

if you noticed it gets easier going to the recent years so inshalla ya rab

 

[Rahma Abdelrahman]

Hey everybody, how was your Biology paper?
I think it was good except for 2 or 3 questions!
(Variant 1)