Biology; Chemistry; Physics: Post your doubts here!

[SALT]

Fallen316
i guess it has to be series...but den the voltmeter connection was confusing too...and wat abt the particle X thingy?

 

[Fallen316]

Fallen316
i guess it has to be series...but den the voltmeter connection was confusing too...and wat abt the particle X thingy?

yes , the particle .
it was downwards.

 

[SALT]

i got tht wrong..i drew it both ways(up n down) to show motion of a transverse wave...
the magnetic field one had to start from coil A nd end at coil A ryt??

 

[Fallen316]

i got tht wrong..i drew it both ways(up n down) to show motion of a transverse wave...
the magnetic field one had to start from coil A nd end at coil A ryt??

not back to coil A
from coil A to B

 

[MaboroshI_I]

not back to coil A
from coil A to B

Now I'm really confused! How did we have to draw it exactly?

 

[Fallen316]

Now I'm really confused! How did we have to draw it exactly?

that's where im being confused too and assuming i'll lose a mark in it.

 

[ashiqbal]

that is why i didnt attempt that question!

 

[Rimsa]

@Fallen316 its series. however the voltmeter should be in parallel but there it was working as a galvanometer.
http://www.xtremepapers.com/community/members/fallen316.12500/

 

[daredevil]

y did u guys attempt the transformer question if u got so confused over it. granted the last parts were easy but the start of the question was screaming "DON"T DO THIS QUESTION" at least that seemed the case to me

 

[daredevil]

heyy guys for chem is aluminium extraction (all with the cryolite stuff) is it included in the syllabus for 2012? if yes then plz give me some notes on it if u have any thanks

 

[syed1995]

Anyone around to help me with Chem MCQs

 

[daredevil]

Anyone around to help me with Chem MCQs

bring it on .... i'll try if i can help

 

[rabiafarooq101]

Anyone around to help me with Chem MCQs

I would help too like my frnd daredevil girl u rock

 

[rabiafarooq101]

heyy guys for chem is aluminium extraction (all with the cryolite stuff) is it included in the syllabus for 2012? if yes then plz give me some notes on it if u have any thanks

It is do you have the chem green book read it from there

 

[rabiafarooq101]

y did u guys attempt the transformer question if u got so confused over it. granted the last parts were easy but the start of the question was screaming "DON"T DO THIS QUESTION" at least that seemed the case to me

same here avoided it

 

[syed1995]

Seriously whoever attempted Q9. commited suicide for reals .. because if he knew everything in Q9, then the other 2 questions would have been more than a Piece of cake .. lol

and who left the last question ?? was the easiest one!

 

[daredevil]

It is do you have the chem green book read it from there

no i don't have it DARN!! :/ can u explain it like if u got time/? tumhari b prep ho jaaye gi hehehe ^__^

 

[rabiafarooq101]

no i don't have it DARN!! :/ can u explain it like if u got time/? tumhari b prep ho jaaye gi hehehe ^__^

sure wait

 

[rabiafarooq101]

Extraction of Aluminum:​

Aluminum exists naturally as aluminum oxide (alumina) in its ore, which is called bauxite. Because aluminum is a very reactive metal, it holds on very tightly to the anion it bonds with, which is oxide in this case. This is why the best way to extract and purify aluminum is by electrolysis in a cell like the one below.​

In this cell, the electrodes are made of graphite (Carbon). The cathode is a layer at the bottom of the cell and the anodes are bars dipped in the electrolyte. The electrolyte in this process is a molten mixture of aluminum oxide and cryolite. Aluminum oxide by its self has a very high melting point of 2050oC which is higher than the melting point of the steel container in which this process is done. That means the steel container will melt before the aluminum oxide. This is why aluminum oxide is mixed with cryolite which decreases the melting point of it to under 1000oC, thus saving a lot of money because heating is expensive and preventing the steel container from melting. Heat must be continuously supplied to the mixture to keep it molten. Aluminum oxide does not conduct electricity when solid because it does not have free mobile ions to carry the charge.​

• Aluminum oxide is purified from impurities of oxide by adding sodium hydroxide
• Aluminum oxide is mixed with cryolite and put in the electrolysis cell
• Heat is given in until the mixture becomes molten
• Electrolysis start
• Oxide ions get attracted to the anode and discharged (oxidation); 2O2-, 4e → O2
• Aluminum ions get attracted to the cathode and discharged and settle at the bottom
  of the container (reduction); Al3+ + 3e → Al
• Oxygen gas evolves and is collected with waste gases
• Aluminum is sucked out of the container at regular intervals

Oxygen gas which evolves reacts with carbon from the cathode forming CO2. The cathode gets worn away. To solve this, the cathode is replaced at regular intervals. Heat supply is very expensive; this is why cryolite is used to decrease the melting point of aluminum oxide and this process is done in plants which use hydroelectric energy because it is cheap​

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HERE YOU GO GOT IT FROM XPS REVISION​

 

[rabiafarooq101]

HOPE it helped