Biology; Chemistry; Physics: Post your doubts here!

[Gohar Awais]

Its also not in Physics Matters nor Physics federal that's why I am confused

i checked it.

 

[funky brat]

Okay, i will!

But Rectifying diodes. Transistors. And all the other stuff. Relay. Bell. I have no idea what all this means. :/
Is this stuff mentioned in Federal physics?

Relay, bell and logic gates is there. I haven't even heard this rectifying thing before let alone seeing it in the book.
And yeah reed switch is also there. Do read it once.
Relay consists of two circuits that are incomplete hence the current does not flow. But when the a small current passes through the first circuit, the other circuit is completed due to magnetic effect and a greater current flows in the large circuit. Relay is used to control devices that need a large amount of current by way of wires and switches used to control small circuits. The same phenomenon occurs in the bell, magnetism is induced and circuit is completed etc.

 

[Dream.Eater]

What is diopter and power of a lens? and what kind of questions will be there regarding it?

Not in the syllabus

 

[Dark Destination]

Do all redox reactions involve loss and gain of electrons?

 

[Awesome12]

Do all redox reactions involve loss and gain of electrons?

Yes, because all redox reactions involve oxidation and reduction

 

[Dark Destination]

Yes, because all redox reactions involve oxidation and reduction

But what about covalent bonding?

H2 (g) + F2 (g) --> 2HF (g)

A covalent bond is formed between these two molecules, and no gain or loss of electrons takes place.
But there is a change in the oxidation state.

 

[Awesome12]

But what about covalent bonding?

H2 (g) + F2 (g) --> 2HF (g)

A covalent bond is formed between these two molecules, and no gain or loss of electrons takes place.
But there is a change in the oxidation state.

H2 ------> H+1 + e- (Oxidation)
F2- + e- -----> F2 (Reduction)

 

[funky brat]

http://maxpapers.com/syllabus-materials/chemistry-5070/attachment/5070_w13_qp_1/
Can somebody please explain 10th and 17th MCQ?

 

[Awesome12]

http://maxpapers.com/syllabus-materials/chemistry-5070/attachment/5070_w13_qp_1/
Can somebody please explain 10th and 17th MCQ?

17) The reaction is in equilibrium. Thus whatever we do, the reaction will do something to kind of like ... uhm 'counteract' it. If we add HCl, the backward reaction will favour, shifting the position of equilibium to the left, causing the white ppt of BiOCl to fade/dissolve

10) This is the structure of hydrazine. However, the answer is the marking scheme is given as D, but I believe it to be C

 

[funky brat]

17) The reaction is in equilibrium. Thus whatever we do, the reaction will do something to kind of like ... uhm 'counteract' it. If we add HCl, the backward reaction will favour, shifting the position of equilibium to the left, causing the white ppt of BiOCl to fade/dissolve

10) This is the structure of hydrazine. However, the answer is the marking scheme is given as D, but I believe it to be C

View attachment 38082

Exactly, I did C too.
Where in the book can I read about this equilibrium reaction thing? Is it in Chemistry Insights?

 

[Awesome12]

Exactly, I did C too.
Where in the book can I read about this equilibrium reaction thing? Is it in Chemistry Insights?

I don't know about the Chemistry Insights. My chemistry teacher gave us a lecture on it, and I had to note down the points during her lecture. Try fundamental or Chemistry matters, it could be there. It is there in the Chemistry book by Richard Harwood.

 

[funky brat]

I don't know about the Chemistry Insights. My chemistry teacher gave us a lecture on it, and I had to note down the points during her lecture. Try fundamental or Chemistry matters, it could be there. It is there in the Chemistry book by Richard Harwood.

Oh okay. I can get Chemistry Matters, though. Does it cover the whole topic?

 

[Awesome12]

Oh okay. I can get Chemistry Matters, though. Does it cover the whole topic?

Sorry but I have no idea about the book. My teacher only told us the name of this book once

 

[funky brat]

Sorry but I have no idea about the book. My teacher only told us the name of this book once

Alright. Thanks anyways.

 

[Dark Destination]

17)
10) This is the structure of hydrazine. However, the answer is the marking scheme is given as D, but I believe it to be C

View attachment 38082

Exactly, I did C too.

The Answer is D. The marking scheme is not wrong.
Their are 2 electrons in the first shell of Nitrogen, that are not involved in bonding, you know.
You forgot to count them?

 

[Awesome12]

The Answer is D. The marking scheme is not wrong.
Their are 2 electrons in the first shell of Nitrogen, that are not involved in bonding, you know.
You forgot to count them?

Oh yeah

 

[funky brat]

https://docs.google.com/gview?url=h...ploads/2012/10/5070_s13_qp_12.pdf&chrome=true
Somebody please explain 19th, 20th and 31st MCQ.

 

[Dream.Eater]

https://docs.google.com/gview?url=h...ploads/2012/10/5070_s13_qp_12.pdf&chrome=true
Somebody please explain 19th, 20th and 31st MCQ.

19th is A since aluminium oxides are amphoteric and carbon dioxide is acidic so they would react with NaOH. Copper and magnesium oxides don't react with bases.

20th is B since if you add more HCl then t pressure on the reactant side increases and is more than that of the product side so eq shifts forwards reducing pressure and making more Cl2

31st is D since O2 is formed at the anode and the O2 reacts with the carbon rods to give CO2. This takes place due to high temp.

 

[funky brat]

19th is A since aluminium oxides are amphoteric and carbon dioxide is acidic so they would react with NaOH. Copper and magnesium oxides don't react with bases.

20th is B since if you add more HCl then t pressure on the reactant side increases and is more than that of the product side so eq shifts forwards reducing pressure and making more Cl2

31st is D since O2 is formed at the anode and the O2 reacts with the carbon rods to give CO2. This takes place due to high temp.

Thank you.

 

[Dream.Eater]

Thank you.

no problem