Biology; Chemistry; Physics: Post your doubts here!

[black widow]

You are welcome

did u even understand what i wrote?

 

[Nabeel.Ahmad]

1. Notes ratto, I have my sir's notes which are perfect
2. Do Past papers with Mark schemes
3. Baqi Allah kay sapurd

Exactly as told to black widow, too bad he didnt like it

But ratta-fying won't help. Technical understanding of the concepts is required.

 

[funky brat]

The third one. Because it has the same NH2 and OH, which are at the end of Di-Alcohols and Di-amines.
Apparently, the monomer below can not react with the second monomer above, because two Carboxylic groups can not fuse together to liberate a water molecule.

This was a tricky question, that requires a clear understanding of the nature of linkages. I selected D, but i was wrong.

Tbh, I still don't get it. I selected B though.

 

[funky brat]

Is it better to read all the books of all subjects completely once and then start with the past papers or I should do them side by side?

 

[Nabeel.Ahmad]

Tbh, I still don't get it. I selected B though.

A Di-Carboxylic acid can react with a Di-Alcohol, because the COOH group and the OH group fuse together to liberate a water molecule. This is the basis of formation of CONDENSATION POLYMERS.
Same is the case with COOH group and NH2 group. A Di-Carboxylic acid can combine with a Di-Amine, to liberate a water molecule.
The OH from COOH, combines with the H from NH2 to form a water molecule, leaving behind C=O-N-H Linkage, which is called AMIDE LINKAGE.

So, monomer shown (Di-Carboxylic acid) can fuse with any molecule that has both OH on its sides, or NH2 on its sides, or one NH2 and OH on either side.
But the second monomer above has NH2 and COOH on its sides. COOH and COOH can't fuse together to liberate a water molecule, the reason for that is beyond the scope of O-Level.

So that is why the monomer shown can react with 3 of the above monomers, not the second one.

Get it?

 

[Nabeel.Ahmad]

Is it better to read all the books of all subjects completely once and then start with the past papers or I should do them side by side?

I'm reading the book first, which i think is better.

 

[funky brat]

I'm reading the book first, which i think is better.

Otherwise, it would take ages to do one subject completely and then move on to the next.

 

[funky brat]

A Di-Carboxylic acid can react with a Di-Alcohol, because the COOH group and the OH group fuse together to liberate a water molecule. This is the basis of formation of CONDENSATION POLYMERS.
Same is the case with COOH group and NH2 group. A Di-Carboxylic acid can combine with a Di-Amine, to liberate a water molecule.
The OH from COOH, combines with the H from NH2 to form a water molecule, leaving behind C=O-N-H Linkage, which is called AMIDE LINKAGE.

So, monomer shown (Di-Carboxylic acid) can fuse with any molecule that has both OH on its sides, or NH2 on its sides, or one NH2 and OH on either side.
But the second monomer above has NH2 and COOH on its sides. COOH and COOH can't fuse together to liberate a water molecule, the reason for that is beyond the scope of O-Level.

So that is why the monomer shown can react with 3 of the above monomers, not the second one.

Get it?

Yes That was simple.

 

[♫Prince Shah♫]

Sorry was tuned up.. M here

 

[black widow]

But ratta-fying won't help. Technical understanding of the concepts is required.

thats what i told him, but he doesn't understand

 

[funky brat]

Why is Iron extracted by reduction with coke rather than electrolysis?

 

[Nabeel.Ahmad]

Why is Iron extracted by reduction with coke rather than electrolysis?

Iron can be extracted by Electrolysis, too. But it would be a very expensive method.
Requires a lot of Electricity.

Chemists found a simpler way of Reducing Iron Ore, to pure molten iron, and that is done by the Blast Furnace.

But for Aluminum Oxide, they have no choice, but to use electrolysis, as Aluminum compounds are very stable, and Aluminum is a reactive metal.

 

[funky brat]

Iron can be extracted by Electrolysis, too. But it would be very expensive method.
Requires a lot of Electricity.

Chemists found a simpler way of Reducing Iron Ore, to pure molten iron, and that is done by the Blast Furnace.

But for Aluminum Oxide, they have no choice, but to use electrolysis, as Aluminum compounds are very stable, and Aluminum is a reactive metal.

I thought this was because it was less reactive than Aluminium. But how am I supposed to know, it's not even written in the book. :|

 

[Nabeel.Ahmad]

I thought this was because it was less reactive than Aluminium. But how am I supposed to know, it's not even written in the book. :|

Was this an MCQ?

It is less reactive than Aluminum, and that's what makes its Reduction in the Blast Furnace possible.
Try throwing Aluminum Oxide into the Blast Furnace, it won't be Reduced.

Yes, it is not written in the book.

 

[♣♠ MagneD ♣♠]

Why is Iron extracted by reduction with coke rather than electrolysis?

the main reason for it is that it is less reactive than carbon so can be easily extracted .. which will be less expensive

 

[black widow]

Why is Iron extracted by reduction with coke rather than electrolysis?

the method of extraction of metals is dependent on their stability
metals in the reactivity series from K to Al are extracted by electroysis
metals from Zn to Lead are extracted by reduction
the remaining metals in the reactivity series are extracted by roasting their ore

remember that the more reactive a metal is, the more stable its compound will be, and the more difficult it is to separate its constituents
for example Al compounds are very stable and cannot be extracted by reduction or by heating
Cu compounds are very unstable and thus can easily be extracted by roasting them in air

 

[Faizan Muhammmad]

But ratta-fying won't help. Technical understanding of the concepts is required.

thats what step 2 is for people ​

First step just ensure you know what to write in atleast 75% questions
Nae mananee baat to na mano, mujhay iss kee tankhwah nae milnee

 

[funky brat]

Was this an MCQ?

It is less reactive than Aluminum, and that's what makes its Reduction in the Blast Furnace possible.
Try throwing Aluminum Oxide into the Blast Furnace, it won't be Reduced.

Yes, it is not written in the book.

I know that but the thing is I chose the wrong option. There was the other option too that Al is more reactive than Fe therefore it is reduced by electrolysis so I definitely went for that option. And yeah this was an MCQ. But how did you know then?

 

[funky brat]

the method of extraction of metals is dependent on their stability
metals in the reactivity series from K to Al are extracted by electroysis
metals from Zn to Lead are extracted by reduction
the remaining metals in the reactivity series are extracted by roasting their ore

remember that the more reactive a metal is, the more stable its compound will be, and the more difficult it is to separate its constituents
for example Al compounds are very stable and cannot be extracted by reduction or by heating
Cu compounds are very unstable and thus can easily be extracted by roasting them in air

I know that, thanks though.

 

[Nabeel.Ahmad]

I know that but the thing is I chose the wrong option. There was the other option too that Al is more reactive than Fe therefore it is reduced by electrolysis so I definitely went for that option. And yeah this was an MCQ. But how did you know then?

For this question, you were supposed to know that Iron Oxide can be electrolysed, too. I mean why can't it be electrolysed? It is an ionic compoud, with Iron and Oxide ions, arranged to form an ionic lattice. Iron Oxide can be melted, and then Molten Iron Oxide can be Electrolysed to get Oxygen at the Anode, Iron at the Cathode, but then why is the BLAST FURNACE used?

Chemists always look for ways to save energy. To save resources. That is why they found an easier way to Extract Iron, a method that does not require huge amounts of electricity. And that is the chemical reduction in the Blast Furnace.