Chemistry: Post your doubts here!

[syed1995]

yeah, you're right. it is 40. Then, I have no idea why it says 130 as maximum marks for AS.

Max marks for P3 are 40

The total marks for the syllabus are indeed 140.. but i think the weightage of P3 is 30 marks...

Look at:

23% at AS Level for P3.. That's only possible if P3 Marks are taken to be 30.

30/(130) *100 = 23%

40/140*100 = 28% .. which is wrong.

I can't say anything else.. lol

 

[Malik777]

The total marks for the syllabus are indeed 140.. but i think the weightage of P3 is 30 marks...

Look at:

23% at AS Level for P3.. That's only possible if P3 Marks are taken to be 30.

30/(130) *100 = 23%

40/140*100 = 28% .. which is wrong.

I can't say anything else.. lol

Go Get A life Bro lol

 

[salvatore]

I'm not sure how I can clarify it but have a look at the Hess's Law diagram.
And not a problem. View attachment 23047
So in this case, the reactants are C and S and product is CS2. that's why in the end, the subtracting takes place.

That's a clear explanation.

Thanks a lot

 

[snowbrood]

do anyone have chemactive a level chemistry worksheets please upload it the site is down for quite a time i wanted those worksheets. and if some has chemistry mark schemes for all past papers compiled please upload

 

[Oliveme]

That's a clear explanation.

Thanks a lot

no problem. I'm glad you understood.

 

[Eng Minhal]

Can I fast track Chemistry AS + A2 in a year?

 

[A*(a*)]

O/N 11/12 question 3
Can anyone who is good in chemistry solve this?
Use of the Data Booklet is relevant to this question.
From which particle is the removal of an electron the most difficult?
A Cl- (g) B F- (g) C K+ (g) D Na+ (g)

 

[A*(a*)]

do anyone have chemactive a level chemistry worksheets please upload it the site is down for quite a time i wanted those worksheets. and if some has chemistry mark schemes for all past papers compiled please upload

Can you answer the question posted above please?

 

[Gémeaux]

O/N 11/12 question 3
Can anyone who is good in chemistry solve this?
Use of the Data Booklet is relevant to this question.
From which particle is the removal of an electron the most difficult?
A Cl- (g) B F- (g) C K+ (g) D Na+ (g)

When an electron is removed from an atom, the nucleus has a stronger hold on the remaining electrons. That is why it is difficult to remove an electron when one has already been removed. This leaves us with option C and D to choose from.
Removal of an electron in the last two cases mentioned involves the second Ionisation Energy.
Use the Data Booklet to check the energy for each, K+ has 3070 while Na+ has 4560 kJ/mol. More energy means it is more difficult to remove an electron.

 

[A*(a*)]

Thankyou so much but how can we be so sure in assuming that Na+ is gaseous?

 

[Gémeaux]

Thankyou so much but how can we be so sure in assuming that Na+ is gaseous?

You're welcome. I didn't have to assume, you wrote it

D Na+ (g)

 

[A*(a*)]

When an electron is removed from an atom, the nucleus has a stronger hold on the remaining electrons. That is why it is difficult to remove an electron when one has already been removed. This leaves us with option C and D to choose from.
Removal of an electron in the last two cases mentioned involves the second Ionisation Energy.
Use the Data Booklet to check the energy for each, K+ has 3070 while Na+ has 4560 kJ/mol. More energy means it is more difficult to remove an electron.

Can you answer this also please? Its from the same year and variant is 13.

 

[A*(a*)]

You're welcome. I didn't have to assume, you wrote it

hahahah I am really sorry , Question STATES that it IS gaseous
Well another related question - Are always ions gaseous?

 

[Gémeaux]

View attachment 23074
Can you answer this also please? Its from the same year and variant is 13.

Sorry but I'm rather unsure about this one yet.

hahahah I am really sorry , Question STATES that it IS gaseous
Well another related question - Are always ions gaseous?

It's okay, with exams coming up that happens too often
No, they can be aqueous too.

 

[A*(a*)]

Sorry but I'm rather unsure about this one yet.


It's okay, with exams coming up that happens too often
No, they can be aqueous too.

hahahah thats true , seriously I never felt such pressure before. I knew this too They can be aqueous too

 

[Gémeaux]

hahahah thats true , seriously I never felt such pressure before. I knew this too They can be aqueous too

If you did already, why ask

 

[Abu mota]

i cant do most of the questions on aldehydes,ketones,carboxylic acids, alcohols and esters on P1 and P2. My problem is that they ask for substances i've never seen. plz tell me an easy way of solving questions like these.

 

[afsah shaikh]

in a equation how do we know which reactant on change in concentration has no effect on the rate of reaction
eg:
CH3CH=CH2 + I2 -------> CH3CHICH2I

PLZ i need to know its important

 

[VelaneDeBeaute]

in a equation how do we know which reactant on change in concentration has no effect on the rate of reaction
eg:
CH3CH=CH2 + I2 -------> CH3CHICH2I

PLZ i need to know its important

We turn to the order of the reaction. If the order is zero, that means that the change in concentration of a reactant has no effect on the rate of reaction.
http://www.chemguide.co.uk/physical/basicrates/orders.html

 

[VelaneDeBeaute]

i cant do most of the questions on aldehydes,ketones,carboxylic acids, alcohols and esters on P1 and P2. My problem is that they ask for substances i've never seen. plz tell me an easy way of solving questions like these.

Hey, don't freak out on seeing alien compounds. That will a part of the exam most of the times. You just need a knowledge of the functional groups. Forget whatever the R chains must be, just focus on how the functional groups are interacting.