Chemistry: Post your doubts here!

[Eugene99]

are they taking the ratio of the changes or sth? Coz Chlorine's oxdn state is decreasing by 2 and Sulphur's by 4 ...
so its B?

Yeah..I also got the same, then I thought they must have made it a ratio but then that's also no rule! so I was so confused, thought I wasn't calculating the oxidation states right, went back to the book, read again and again, read on the web, on chemguide then listened khanacademy...everything actually! but still....so this is it the question was wrong...I just found these topicals on the web but seems like they aren't authentic enough and questions can be wrong!

This is the actual MCQ from past papers Eugene99
View attachment 59161

Yeah...this is it! Thanks a lot!
I have a topical MCQs book for chemistry, "1000 chemistry MCQs with Help", but I found that questions set there contain syllabus from A2, which must be part of AS in old syllabus...any idea?

 

[Rizwan Javed]

Yeah..I also got the same, then I thought they must have made it a ratio but then that's also no rule! so I was so confused, thought I wasn't calculating the oxidation states right, went back to the book, read again and again, read on the web, on chemguide then listened khanacademy...everything actually! but still....so this is it the question was wrong...I just found these topicals on the web but seems like they aren't authentic enough and questions can be wrong!

Yeah...this is it! Thanks a lot!
I have a topical MCQs book for chemistry, "1000 chemistry MCQs with Help", but I found that questions set there contain syllabus from A2, which must be part of AS in old syllabus...any idea?

Yes, some topics in that book do contain question which relate to A2. However it is good for practice. Do this book for practice only, but focus more on the yearly ones.

 

[zahra azam]

Use hess's law to calculate the standard enthalpy change of hydration of MgSO4
I know the method but answer is not correct
Can anyone explain it to me? :3

 

[sj0007]

http://maxpapers.com/wp-content/uploads/2012/11/9701_s13_qp_42.pdf

q:8a (iii)..why is that structure?
8c(i): how come there's no reduction in OH?

8a) (iii) By cross linking polymer chains it means, the link between the polymer chains which would be the same chains up and down............ so the cross link between them: HOCH2(CH2OH)C(CH2OH) CH2OH (thus the power 4 in the ms). The H at the top and bottom come because we r talking about it individually, when combined, the COO gets attached instead.
8c(i) They cause no reduction because they already have OH groups, because the cross linking itself has two OH's, plus, the question says that not every one available side chain is......

Hope it helps

 

[Mr.Physics]

Use hess's law to calculate the standard enthalpy change of hydration of MgSO4
I know the method but answer is not correct
Can anyone explain it to me? :3

Which paper ?

 

[sj0007]

Why is the answer D?

 

[zahra azam]

Which paper ?

Book qs :/

 

[Mr.Physics]

Book qs :/

Pg ?

 

[zahra azam]

Pg ?

Its not out textbook
Its a qs i found on a diff book on internet

 

[donewithtime80]

8a) (iii) By cross linking polymer chains it means, the link between the polymer chains which would be the same chains up and down............ so the cross link between them: HOCH2(CH2OH)C(CH2OH) CH2OH (thus the power 4 in the ms). The H at the top and bottom come because we r talking about it individually, when combined, the COO gets attached instead.
8c(i) They cause no reduction because they already have OH groups, because the cross linking itself has two OH's, plus, the question says that not every one available side chain is......

Hope it helps

thanx

 

[sj0007]

thanx

Welcome

 

[nehaoscar]

Small doubt which may seem silly
S14-41-Q2-b-ii
So they ask for the units of k

Now is amt^-2 same as mol^-3dm^3 ??

 

[a_wiserME!!]

why is order 1 with respect to [H+]?? TIA

 

[Konstantino Nikolas]

View attachment 59249

why is order 1 with respect to [H+]?? TIA

Consider Experiment 3 and 4

0.2/0.25 = 0.8
3.2/2 = 1.6

We know order is 1 with respect to [CH3CHO] , but rate is double when [CH3OH] is kept constant. This means that rate is increasing twice due to order being 1 with respect to [H+] also.

 

[Konstantino Nikolas]

Small doubt which may seem silly
S14-41-Q2-b-ii
So they ask for the units of k
View attachment 59248
Now is amt^-2 same as mol^-3dm^3 ??

never come across rate eqn using pressure :O
The units of rate = atm s^-1 always in case of pressures, is it?
And i don't think we can equate the mol dm^-3 here since 24 dm^3 of gas is only 1 mol ... not sure though

 

[nehaoscar]

never come across rate eqn using pressure :O
The units of rate = atm s^-1 always in case of pressures, is it?
And i don't think we can equate the mol dm^-3 here since 24 dm^3 of gas is only 1 mol ... not sure though

Oh right i forgot it was pressure!
I was thinking of concentrations for some reason ... :/
Thanks!

 

[Konstantino Nikolas]

Oh right i forgot it was pressure!
I was thinking of concentrations for some reason ... :/
Thanks!

yeah coz we usually use concentrations that's why
no problem xD

 

[a_wiserME!!]

Consider Experiment 3 and 4

0.2/0.25 = 0.8
3.2/2 = 1.6

We know order is 1 with respect to [CH3CHO] , but rate is double when [CH3OH] is kept constant. This means that rate is increasing twice due to order being 1 with respect to [H+] also.

Is it like as if to say that with respect to [CH3CHO] it's 1 and so only if its is 1 with respect to [H+], both together can double the rate?? like 1+1 =2??

 

[FranticAmaze]

Is it like as if to say that with respect to [CH3CHO] it's 1 and so only if its is 1 with respect to [H+], both together can double the rate?? like 1+1 =2??

https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-753#post-950818

awesomaholic101 ruby_fern donewithtime80 this was the other explanation we were talkin about in class today

 

[Konstantino Nikolas]

Is it like as if to say that with respect to [CH3CHO] it's 1 and so only if its is 1 with respect to [H+], both together can double the rate?? like 1+1 =2??

you got it