Chemistry: Post your doubts here!

[Muhammad Bin Anis]

cmon ofcourse ichecked d mark scheme..!! ididnt get a wrd..!!pchhh...nai smajh ra he...

chalo i am giving it a try

amino acids contain the -NH2 group . when the solution is acidic (i.e H+ ions are present), nitrogen in the the -NH2 group uses iits lone pair of electrons and attracts the H+ ion.. a dative covalent bond is formed and the charge on the molecule is is increased by +1 so the spot moves towards the negative electrode(cathode)

in case the solution becomes more alkaline, the COOH ggroup loses its hydrogen in the form of H+ ions to nuetralise the ffect of base (OH- ions and H+ ions react to form water)
but the charge on the original molecule has decreased by 1 , it is attarcted to the anode (pos. electrode)

This way electrophoresis is dependant on the pH

 

[sumaiyarox:)]

u

chalo i am giving it a try

amino acids contain the -NH2 group . when the solution is acidic (i.e H+ ions are present), nitrogen in the the -NH2 group uses iits lone pair of electrons and attracts the H+ ion.. a dative covalent bond is formed and the charge on the molecule is is increased by +1 so the spot moves towards the negative electrode(cathode)

in case the solution becomes more alkaline, the COOH ggroup loses its hydrogen in the form of H+ ions to nuetralise the ffect of base (OH- ions and H+ ions react to form water)
but the charge on the original molecule has decreased by 1 , it is attarcted to the anode (pos. electrode)

This way electrophoresis is dependant on the pH

jazakallahu khairan...may Allah reward u for ur goodness!! .......i gt it!!!

 

[Muhammad Bin Anis]

u

jazakallahu khairan...may Allah reward u for ur goodness!! .......i gt it!!!

check this out. this gonna help you alot

http://www.chemguide.co.uk/CIE/section112/learninga.html#top

 

[sumaiyarox:)]

check this out. this gonna help you alot

http://www.chemguide.co.uk/CIE/section112/learninga.html#top

jazakallah again bro..

 

[yubakkk]

 

[yubakkk]

please explain me above q.

 

[yubakkk]

 

[yubakkk]

why not answer is A?

 

[A*(a*)]

question 1,
1 mole = 6.02*10^23 particles
n(H atoms)= mass/ Mr * 2 ( multiply by 2 since we are talking about atoms not molecules)
=1/2 *2 =1 mole=6.02*10^23
Only option C has 1 mole Neon ATOMS! which is equal to 6.02*10^23 atoms!
I hope I didn't confuse u, right?

 

[A*(a*)]

boiling point is determined by forces between molecules, The H-F bond doesn't break at all! The forces (hydrogen bonding ) BETWEEN THE MOLECULES break!

 

[gary221]

please explain me above q.

In 1g of hydrogen, moles of H2 = mass of H2/Mr of H2 = 1/2 = 0.5 moles
No of molecules of H2 = moles * (6.02*10^23) = 0.5 * (6.02*10^23) = 3.01*10^23 molecules
So, no of atoms of H2 = 2 * no. of molecules ie 6.02 * 10^23 atoms
And only Ne atoms equal the no. of H2 atoms (using the abv eqns)
So, ans = C

 

[Warrior66]

Asalam-o-Alaikum!
can anyone please help me with these
questions? http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_11.pdf
Questions: 9, 21, 26 and 28
thanks a lot..!

 

[19islandprincess96]

Can u explain question 2(iv) of O/N/11 of chemistry p41?

 

[lyuchenqujoy]

Equilibrium constant does not change when you change the pressure of a system. The only factor that affects the equilibrium constant is temperature.
The equilibrium constant is just a ratio of the product of the products to the product of the reactants.. right? Now increasing the pressure of the reactant unbalances the equilibrium because more products are formed. The concentration of products will increase until a new equilibrium is reached when the value of the equilibrium constant gets back to what it was before (The value remains the same).

In conclusion, the equilibrium "constant" is always constant unless the pressure is changed.

yeah I know. But according to your reply, when we change the temperature, there should also be a new equilibrium, so the equilibrium constant should remain unchanged..... Oh my gah I am totally confused TAT

 

[Raiyan3]

Please help with question no. 5, 10, 12, 21
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_11.pdf

 

[Muhammad Bin Anis]

yeah I know. But according to your reply, when we change the temperature, there should also be a new equilibrium, so the equilibrium constant should remain unchanged..... Oh my gah I am totally confused TAT

read the whole stuff from the link
http://www.chemguide.co.uk/physical/equilibria/change.html#top
its worth spending your 15 minutes

 

[salvatore]

yeah I know. But according to your reply, when we change the temperature, there should also be a new equilibrium, so the equilibrium constant should remain unchanged..... Oh my gah I am totally confused TAT

Yeah.. exactly! I asked my teacher the same question, but she said that it needs knowledge which is beyond A levels
So just remember:
When the forward reaction is exothermic, increasing the temperature decreases the value of the equilibrium constant.
When the forward reaction is endothermic, increasing the temperature increases the value of the equilibrium constant.

 

[abruzzi]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_23.pdf
Please help me with question no. 4(b)iii.. how do you know which one is the electrophile?
Thanks

 

[nodyed]

How to decide energy given out by various compounds on combustion, for example if we combust alcohol and ethene so which one is likely to give more energy, is only calculation energy change is the way? or we can decide through general knowledge in either case let me know the solution for it?

 

[nodyed]

At a total pressure of 1.0 atm, dinitrogen tetraoxide is 50% dissociated at a temperature of 60 degree C, according to the following equation.
N2O4 ==> 2NO2
What is the value of the equilibrium constant, Kp, for this reaction at 60 degree C?
A) 1/3 atm
B) 2/3atm
C) 4/3atm
D) 2atm

Answer is C
but how is the question??