Biology; Chemistry; Physics: Post your doubts here!

[Nabeel.Ahmad]

Cl2 + 2kBR

Cl2 is a covalent molecule.
Chlorine gas consists of Cl2 molecules, which are far apart. That is what we call an element.

Potassium Bromide is an ionic compound, with the formula --> KBr.
This formula was calculated using the swapping of valencies method. K+ and Br-
You swap the valencies and you get KBr.

Now, the reaction is Cl2 + 2KBr.

Chlorine gas is reacting with Potassium Bromide. Now, this is a displacement reaction. Chlorine is more reactive that Bromine, so Chlorine will displace Bromine from Potassium Bromide and Bromine will be released separately.

The full reaction is:

Cl2 + KBr --> KCl + Br2
Chlorine + Potassium Bromide --> Potassium Chloride + Bromine.

When we balance this equation, we add 2 with KBr, as there are two Br on the right hand side.
And we add 2 with KCl as there are two K and two Cl on the left hand side.
This is called BALANCING in Chemistry.
Due to this BALANCING, we get those numbers with the formulas.

Hope you understand now!

 

[ZohaKhan]

in chapter "Excretion"... do we have to prepare urine formation as well n the funtions of the components of d human urinatry system? syllbs doesnt require it but stil m cnfused dat wot do v hav to prep in dis chap n wot not?
HELP!

 

[Maganius]

Im bit weak in Chem; need help

 

[Ram97]

Im bit weak in Chem; need help

Chemistry as a whole subject or some specific topics???

 

[Maganius]

Chemistry as a whole subject or some specific topics???

Whole
Well ik the basics but feel difficulty in solving theory section of each chapter

 

[ZohaKhan]

REplyyyyy

 

[ZohaKhan]

REplyyyyy

 

[***amd***]

in chapter "Excretion"... do we have to prepare urine formation as well n the funtions of the components of d human urinatry system? syllbs doesnt require it but stil m cnfused dat wot do v hav to prep in dis chap n wot not?
HELP!

in cie.sw, my teacher said, there jave been Qs of those topics which are clearly stated in syll as "not included". so u better prepare it too.

 

[noor-ul-iman]

In a sample of air at 25 oC, the molecules of oxygen, nitrogen and carbon dioxide all move with
different average speeds.
Which of the following lists the molecules in order of decreasing average speed?
fastest slowest
A carbon dioxide oxygen nitrogen
B nitrogen oxygen carbon dioxide
C oxygen carbon dioxide nitrogen
D oxygen nitrogen carbon dioxide

 

[Uniquely Beautiful]

In a sample of air at 25 oC, the molecules of oxygen, nitrogen and carbon dioxide all move with
different average speeds.
Which of the following lists the molecules in order of decreasing average speed?
fastest slowest
A carbon dioxide oxygen nitrogen
B nitrogen oxygen carbon dioxide
C oxygen carbon dioxide nitrogen
D oxygen nitrogen carbon dioxide

- calculate the Mr of all the gases..the one with lightest weight would be the first one,
the ans is B

 

[noor-ul-iman]

thnkx!!!!!!!!

 

[Richard63]

Hi, can anyone please help me take a look at this Physics O level question from the website below or the picture attached:

http://postimg.org/image/egjllgt4l/
It is regarding AC transmission involving voltage supplied and power used.

Any explanation is very appreciated, Thank you very much!

 

[Talha Farooqui BSS]

Im bit weak in Chem; need help

what help u need

 

[Maganius]

what help u need

Need notes of Organic Chem

 

[Talha Farooqui BSS]

Need notes of Organic Chem

 

[Talha Farooqui BSS]

Need notes of Organic Chem

 

[Maganius]

thanks a lot mate

 

[noor-ul-iman]

what is the formula of deceleration? give me an example plzzz...
plzz help me!!

 

[funky brat]

what is the formula of deceleration? give me an example plzzz...
plzz help me!!

It's the same as for acceleration which is v-u/t where v is the final velocity, u is the initial velocity and is time. Deceleration is therefore always negative.

 

[irfan.kheerdali]

hey guys what r the grading system for cambridge o level nov 2013 papers?????