Biology; Chemistry; Physics: Post your doubts here!

[Spidey21]

That big list man, better do'em all!
Why leave a few behind?

why depend on a guess papers??

 

[asd]

why depend on a guess papers??

...
Am I? Dude he posted that big list for a guess..I said to do all the past papers when only a few were left (that weren't there in the "merchant's" list) lmao.

 

[Spidey21]

...
Am I? Dude he posted that big list for a guess..I said to do all the past papers when only a few were left (that weren't there in the "merchant's" list) lmao.

i am supporting you

 

[syed1995]

Do All of 2008-11

and you should be fine.

 

[syed1995]

June 2009 Q8 (c) ..

Please can anyone help me and EXPLAIN why that would happen instead of the color being Colourless?

 

[Ahmedfj]

June 2009 Q8 (c) ..

Please can anyone help me and EXPLAIN why that would happen instead of the color being Colourless?

the solution S constantly reacted with potassium manganate and gave colorless solution but in the end when no solution S was left in the flask then potassium manganate gave purple colour

 

[Ahmedfj]

June 2009 Q8 (c) ..

Please can anyone help me and EXPLAIN why that would happen instead of the color being Colourless?

June 2003 question 10 part g

 

[khizer shahab]

June 2003 question 10 part g

blue

bcuz the concentration is not changing and amount of copper ions are still in the solution ..!!

 

[khizer shahab]

guys i am anable to understand this procedure pls help me ...!

http://www.xtremepapers.com/papers/...l O Level/Chemistry (5070)/5070_w11_qp_41.pdf

question no. 6

help soon

 

[khizer shahab]

I got a better guess paper. June 2000-2011 and Same for november.

source ...???

 

[syed1995]

guys i am anable to understand this procedure pls help me ...!

http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Chemistry (5070)/5070_w11_qp_41.pdf

question no. 6

help soon

20% of the air is Oxygen .. and Oxygen reacts with heated copper.

so 80% of air will be left .. and 80% of 100cm3, that is 80 cm3. so D

Hope that helps.

 

[khizer shahab]

20% of the air is Oxygen .. and Oxygen reacts with heated copper.

so 80% of air will be left .. and 80% of 100cm3, that is 80 cm3. so D

Hope that helps.

really helped

 

[syed1995]

Which Catalyst is used for each of these Organic reactions .. ?

Compound Catalyst?
Fermentation

Hydrogenation
Hydrolysis
Hydration
Cracking
Addition
Substitution
Esterification
Polymerisation
Fractional Distillation of Crude Oil
Dehydration

Did i missed anything? now tell me which catalyst is used for each if there is any used....

 

[Aamynims]

how do we know whic reagent is in access and which is not? please explain.

 

[Spidey21]

how do we know whic reagent is in access and which is not? please explain.

you calculate the moles of both and you calculate as to which needs how much and then you see that which is more than required...samajh aya??

 

[Aamynims]

yeps thanqu

 

[Spidey21]

Which Catalyst is used for each of these Organic reactions .. ?

CompoundCatalyst?
Fermentation

Hydrogenation - Nickel
Hydrolysis
Hydration
Cracking - Al2 O3
Addition
Substitution
Esterification
Polymerisation
Fractional Distillation of Crude Oil
Dehydration

Did i missed anything? now tell me which catalyst is used for each if there is any used....

contact process - V2O5 (vanadaium 5 oxide)

 

[Aamynims]

contact process - V2O5 (vanadaium 5 oxide)

Which Catalyst is used for each of these Organic reactions .. ?

CompoundCatalyst?
Fermentation

Hydrogenation
Hydrolysis
Hydration
Cracking
Addition
Substitution
Esterification
Polymerisation
Fractional Distillation of Crude Oil
Dehydration

Did i missed anything? now tell me which catalyst is used for each if there is any used....

hydrogenation: nickel
hydrolysis : i think NAOH.. not sure
hydration ?
esterification: concentration sulphuric acid.
fermentation : yeast

 

[syed1995]

What Catalysts are used for what processes ?

Vanadium V Oxide for Contact Process
Iron For Haber
Nickel For Hydrogenation
Esterification: Conc. H2SO4
Fermentation: Yeast ..
Hydrolysis: NaOH
And ... ?

 

[syed1995]

guess everyone's asleep i am headed to bed too .. Good Luck All!

btw if somebody is still around .. can they explain June 2010 Q10 (f) to me?