Chemistry: Post your doubts here!

[{#}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

 

[anastasia grey113]

View attachment 63506
How to do part(ii)
Anyone?

Well for this just equate the reaction constant because it will be the same.
For two equations from any of the two reactions (ill be using 2 and 3) by making k the subject
they will be as follows
1- k = 2/0.2^1 x o.o15^n
2- k =8/0.4^1 x 0.030^n
equate them and the following equation will form
8/0.4^1 x 0.030^n = 2/0.2^1 x o.o15^n
find the value of n.
I used one for the other reactnat becuz v calculate its order in part i) already and its 1.

 

[Holmes]

Well for this just equate the reaction constant because it will be the same.
For two equations from any of the two reactions (ill be using 2 and 3) by making k the subject
they will be as follows
1- k = 2/0.2^1 x o.o15^n
2- k =8/0.4^1 x 0.030^n
equate them and the following equation will form
8/0.4^1 x 0.030^n = 2/0.2^1 x o.o15^n
find the value of n.
I used one for the other reactnat becuz v calculate its order in part i) already and its 1.

thanks

 

[abbas haider]

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

yeah this

NH4+ H20<--› NH3 + H+(or h30+) (the equilibrium sign was a must)

 

[harishassan1399]

What is the product with Br2 and how is it formed?

 

[PixelsLevls]

What is the product with Br2 and how is it formed?

Phenol is very reactive because a lone pair from oxygen over laps with the delocalised pi system in the benzene ring.
Usually for benzene to react with Bromine we require bromine as a pure liquid and a catalyst
But with phenol an aqueous solution works! As it is more reactive and has a higher charge density.

The hydroxide group is a ortho para director. This means that any incoming group will be placed in the 2, 4 and/or 6 position. You will understand what i mean if you see the picture.
As 6 is already occupied only 2 and 4 will be used by bromine

 

[Mts.99]

yeah this

NH4+ H20<--› NH3 + H+(or h30+) (the equilibrium sign was a must)

what where the state symbols? all aq?

 

[abbas haider]

yeah this

NH4+ H20› NH3 + H+(or h30+)

what where the state symbols? all aq?

all aqueous excpet h20 (l)

 

[A*****]

all aqueous excpet h20 (l)

And mentioning H2O wasn't compulsory...right?

 

[Kanekii]

And mentioning H2O wasn't compulsory...right?

I think it was compulsory since it specifically stated to write an equation of ammonium with water.
Besides no need to dwell on the past whats best right now is to prepare for the next papers.
So how is everyone's chem p1 going along?
I always get stuck with organic mcqs any tips?

 

[abbas haider]

And mentioning H2O wasn't compulsory...right?

i am not sure about that ...but since the question asked "Chemical equation" not "ionic equation" I think h20 was compulsary.

 

[A*****]

I think it was compulsory since it specifically stated to write an equation of ammonium with water.
Besides no need to dwell on the past whats best right now is to prepare for the next papers.
So how is everyone's chem p1 going along?
I always get stuck with organic mcqs any tips?

Tym is a big issue in P1...but we've got much tym to prepare for that
Best tip is to practise as much as possible

 

[A*****]

The question said, write an equation, including state symbols, to show THIS behaviour of ammonium...so I think that both will be acceptable bqz showing the behaviour of ammonium was important and the equation must have been linked to our explanation so if we explained in terms of H+ ions, then writing the equation including only H+ and excluding H2O will be acceptable....No??

 

[Cherry lava]

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

If p2 is easier p4 is expected to be more difficult ?
How true is this rumor ???

 

[anastasia grey113]

If p2 is easier p4 is expected to be more difficult ?
How true is this rumor ???

well yes they make a balanced paper for those who appear in the same session so that the threshold is not too high nor too low
so this could be a possibility