Chemistry: Post your doubts here!

[LonelyStudent]

Here’s a good question. When they ask us to draw the structure of any molecule, should we ALWAYS draw its skeletal structure?

 

[IwanttopassAlevel]

they specify the structure

 

[LonelyStudent]

they specify the structure

If they don’t?

 

[A*****]

Wasn't the paper so damn easy today?? I expect the thresholds to be really high

 

[A*****]

If they don’t?

We can draw any of them

 

[aloo Kha]

paper 22 might have been the easiest paper in history
completed in less than 25 minutes

 

[Tauqir_hamed]

Does anyone remember the bronsted lowry acid question ? What did it actually say? Will this equation work : NH4+ + OH- > NH3 + H2O ,.

 

[Kanekii]

Does anyone remember the bronsted lowry acid question ? What did it actually say? Will this equation work : NH4+ + OH- > NH3 + H2O ,.

I think if i remember correctly it was about weak acids brownsted theory for it i wrote:
Acids whose H+ ions dissociate incompletly in aqueous solution. Is it right?
And for equation: NH4 + H20= NH4OH + 0.5H2

 

[abbas haider]

I think if i remember correctly it was about weak acids brownsted theory for it i wrote:
Acids whose H+ ions dissociate incompletly in aqueous solution. Is it right?
And for equation: NH4 + H20= NH4OH + 0.5H2

no
you have wrote the definition of a weak arehenius acid
arhenius acid = a substance that dissolves in water to form H+ ions
bronsted lowery acid = proton doner (these acids can exist in any state not only aqueous)

anyways the definiton should have been

A weak bronsted lowery acid is one which partially donates proton.

 

[Kanekii]

no
you have wrote the definition of a weak arehenius acid
arhenius acid = a substance that dissolves in water to form H+ ions
bronsted lowery acid = proton doner (these acids can exist in any state not only aqueous)

anyways the definiton should have been

A weak bronsted lowery acid is one which partially donates proton.

But H+ ions are protons but i guess you're right about existing in any state

 

[abbas haider]

I think if i remember correctly it was about weak acids brownsted theory for it i wrote:
Acids whose H+ ions dissociate incompletly in aqueous solution. Is it right?
And for equation: NH4 + H20= NH4OH + 0.5H2

Check this reaction amonia is acting as an acid even though its a gas....arhenius theory(what you leant in o levels) can t explain this
Thats why In A levels They taught you Bronsted Lowery Theory of Acids..

 

[Tauqir_hamed]

abbas haider could you tell me whether that equation will work or not? ( the one that I have written above i.e. NH4 + + OH- --> NH3 + H2O. ) Did todays question specifically ask to show between NH4+ and H2O.. could you please tell me.. I am talking about varient 22

 

[A*****]

Wasn't the equation:
NH4+ —› NH3 + H+ ??

 

[Fardeen3342]

can someone help with this I don't get the concept behind it

 

[{#}324354]

What if I wrote lithium tetrahydridoborate instead of lithium tetrahydroborate?? Would I get the mark?

And on page 9, the answer was optical isomerism?

 

[Holmes]

If they don’t?

It's better that you draw a skeletal structure (AS chem)

 

[Holmes]

Would you mind telling me how to find the Atomisation energy of gases? I always mix when to multiply and when to divide.
anastasia grey113

 

[Holmes]

How to do part(ii)
Anyone?

 

[anastasia grey113]

Would you mind telling me how to find the Atomisation energy of gases? I always mix when to multiply and when to divide.
anastasia grey113

well atomisation is basically the half of bond energy for diatomic molecules such as O2 or Cl.
You see Hat is actually the enthalpy when 1 mole of atoms is produced.
But Bond energy is the enthalpy when one mole of bonds is broken.
So suppose if v break 1 mole of bonds of Cl2 or O2 then v will get 2 moles of atoms of each.
So to reduce it to one mole and make it Hat v dicide B.E. by 2.

 

[Holmes]

well atomisation is basically the half of bond energy for diatomic molecules such as O2 or Cl.
You see Hat is actually the enthalpy when 1 mole of atoms is produced.
But Bond energy is the enthalpy when one mole of bonds is broken.
So suppose if v break 1 mole of bonds of Cl2 or O2 then v will get 2 moles of atoms of each.
So to reduce it to one mole and make it Hat v dicide B.E. by 2.

ok getting something now