Biology; Chemistry; Physics: Post your doubts here!

[syed1995]

yes
try reading these. they contain all these points. i g2g actually. sorry
http://www.xtremepapers.com/revision/gcse/chemistry/acids_bases_and_salts.php

Thanks alot

 

[legion]

oh my bad .. xD



thanks alot .. so CO is the only neutral oxide and Al2O3 PbO and ZnO the only amphoteric oxides ?

btw, read equations of reaction of amphoteric oxides from federal book if u have it. the one by preston

 

[legion]

Thanks alot

no problem
we are all here to help and exchange knowledge. no need to thank

 

[GetSomeLife]

Well halides are compounds of halogens ... so whatever the solubility is for chloride it is for all of them ..

Actually, chlorine is soluble in water as 7.1 g in 1 kg of water.
Bromine, on the other hand, is less soluble as 3.41 g of it can be dissolved in 1 kg of water.
Iodine is minimally soluble as 0.0003 g of it can be dissolved in 1 kg.


From these stats, the solubility decreases down the group!

isn't Ca(OH)2 Insoluble ?

Yes, as mentioned before by glamgurl, they are sparingly soluble.

Which of the oxides are neutral I know carbon monoxide is one of the neutral oxides ..

I think you know they are oxides which react neither with acids nor with alkalis!
Examples include:

Carbon monoxide (CO)
Nitrogen monoxide (NO)
Water (H2O)

and which of them are amphoteric ? Aluminium Oxide , Lead(II)Oxide and Zinc Oxide are the only ones right?

Right.

 

[syed1995]

Thanks alot GetSomeLife ..

Well one last question .. can someone list the most conman catalysts and in what reactions they are used .. ?

Like Iron is the catalyst used in the Haber process .. If there is a list can anyone link me to it? thanks !

 

[Gémeaux]

hi there im searching for oct/nov 9700 biology papers and the ms as well as chemistry 9701..any help?

http://www.xtremepapers.com/communi...apers-marking-schemes-examiner-reports.11543/

 

[syed1995]

Thanks alot GetSomeLife ..

Well one last question .. can someone list the most conman catalysts and in what reactions they are used .. ?

Like Iron is the catalyst used in the Haber process .. If there is a list can anyone link me to it? thanks !

vanadium oxide is used as a catalyst in the Contact process .. which are the other catalysts?

 

[shamiza mohamed]

thanx a million...

 

[nightmaressana]

can anyone tell me why we only use AC current for a transformer? cant D.C be used here also?

 

[leadingguy]

can anyone tell me why we only use AC current for a transformer? cant D.C be used here also?

tansformer works on the experiment of farady's rings experiment! remember the experiment???

he had discovered that current is undeced in the other side of the ring only when theres a change in the magnetic field. means We have to change the magnetic field continously to supply current.

now the problem is that how to change magnetic field????

field changes with the change in direction of motion of electrons


so we need to use a A.c power supply to change the direction of current and to generate magnetic field for the current induction on the other side! so its compulsory to use an A.c supply\


is it clear???

 

[nightmaressana]

yes..... but the thing is, we havent done the faraday's ring experiment. my teacher said it wasnt in the syllabus. so we just have done transformer, lenz's law and the ac generator and dc motor.

 

[snowbrood]

can anyone tell me why metals exist as atoms???

 

[syed1995]

can anyone tell me why metals exist as atoms???

I didn't quite get your question ?.. All Non-metals , metals exist in the form of atoms ..

 

[leadingguy]

yes..... but the thing is, we havent done the faraday's ring experiment. my teacher said it wasnt in the syllabus. so we just have done transformer, lenz's law and the ac generator and dc motor.

its not that much difficult you can find it in book just go through it once! use "Charles Chew"

 

[snowbrood]

I didn't quite get your question ?.. All Non-metals , metals exist in the form of atoms ..[/quote

 

[snowbrood]

I didn't quite get your question ?.. All Non-metals , metals exist in the form of atoms ..

i mean why do they exist as monoatomic ??

 

[syed1995]

i mean why do they exist as monoatomic ??

That is because metals only make Ionic bonds , and for an element to exist as a diatomic element , they need to be covalently bonded.

The seven diatomic elements are ..

• Hydrogen (H2)
• Nitrogen (N2)
• Oxygen (O2)
• Fluorine (F2)
• Chlorine (Cl2)
• Iodine (I2)
• Bromine (Br2)

although i am pretty sure that it is not in our syllabus that "Why do they make or do not make diatomic elements"

 

[legion]

That is because metals only make Ionic bonds , and for an element to make a diatomic molecule, they need to be covalently bonded.

Only Elements which are Gases (except Noble Gases) and Halogens are present in the diatomic form.

so NaCl isnt a diatomic molecule?

 

[syed1995]

so NaCl isnt a diatomic molecule?

No ! .. nor are any other Ionic/Covalent compounds .. the only diatomic elements are those elements which end in -gen ( that's how i remember it)

-Halogens
-Nitrogen N2
-Oxygen O2
-Hydrogen H2

The compounds containing these elements are not diatomic either .. only these elements exist in diatomic form.

Like Potassium exists as K in nature , similarly Nitrogen and other diatomic elements occur in N2 form instead of N.


Depends on the way which that word is used really .. Diatomic can also mean a compound containg 2 atoms .. in which case what you have written will be correct , but i don't think the question which snowboard asked would be about that.


PS: I have edited my post to change it , thanks glamgurl for pointing it out

 

[Birdie Honey]

Oh it isn't mentioned? i didn't c it... but to b on the safe side i wud suggest that u do it ... its not that difficult either.

as we go deep its does become difficult!!!!so this why i asked.