Biology; Chemistry; Physics: Post your doubts here!

[asadalam]

Hey guys check this out
http://wiki.answers.com/Q/How_do_you_test_a_liquid_for_alcohol?#slide=2

So if you get tunn its alcohol?

 

[shoaib672002]

This is olevel thread not IGCSE .-.

Thanks

 

[kirann]

how to do it?

 

[DaniyalK]

how to do it?View attachment 43263

There are 4 moles of water in 72g and 4 moles of O. Mass = Moles * mr = 4 * 16 = 64

 

[kirann]

i think the answer shouLd be C, HOW come its B??

 

[DaniyalK]

i think the answer shouLd be C, HOW come its B??
View attachment 43270

A precipitate would definitely have been seen if was was Ca+2 because it does not dissolve in excess.

 

[kirann]

There are 4 moles of water in 72g and 4 moles of O. Mass = Moles * mr = 4 * 16 = 64

4 MOLES OF O? HOW?

 

[kirann]

A precipitate would definitely have been seen if was was Ca+2 because it does not dissolve in excess.

but they are not asking about excess sodium hydroxide

 

[DaniyalK]

4 MOLES OF O? HOW?

72/18 = 4 moles of water
That's 4 moles of H2O, so O is 4 moles.

 

[DaniyalK]

Too quickly means he added too much (you have to add a few drops if you don't want it to dissolve)

 

[kirann]

72/18 = 4 moles of water
That's 4 moles of H2O, so O is 4 moles.

and H is 2*4=8 moles ?

 

[peacce]

they'll cut off the extra words and then read it.
how much did u exceed?

kafi igues

 

[peacce]

If u see the ms it says marks are given for OWN WORDS and USE OF LANGUAGE. I dont think marks would be deducted.
I forgot to write no.of words but it was under the limit

Allah aesa he ho :'(

 

[peacce]

Chem k lye kia karhay ho doston what years r u guys focusing?
m super duper tensed

 

[DaniyalK]

and H is 2*4=8 moles ?

Yeah

I have the English revision guide which is written by CIE examiners and according to that, they don't deduct marks for not writing the number of words. However, they won't read anything past 160, so you can't score any marks on that.

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s09_qp_2.pdf
A6 part d anyone? It's so weird.

 

[peacce]

why C?

 

[peacce]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s09_qp_2.pdf
A6 part d anyone? It's so weird.

industrial wastE? umm thnk wot industrial wste could hav ? iron?

 

[DaniyalK]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s09_qp_2.pdf
A6 part d anyone? It's so weird.

K+ and H+ won't do anything with NaOH. Fe+2 gives a green ppt and Ca+2 gives white ppt.

 

[DaniyalK]

why C?

Sea water contains water mixed with salts. Air is a mixture of gases.