Chemistry: Post your doubts here!

[Warrior66]

I've read in E.N.Ramsden that H2+I212HI and Kc=[HI]2/[H] But in a cambridge course book I've read this equation(Attachment). Which one is correct and in case both are correct then Kc is equal to its reciprocal. And if it is not then how can be the Kc different for a reversible reaction in same conditions?

Asalam-o-Alaikum!
look, when the equation is H2+I212HI then the expression for Kc is [HI]^2/[H2] x [I2]
BUT when the equation is 2HI1H2+I2 then the expression for Kc is [H2] x [I2]/[HI]^2
because the products ALWAYS go on the top and the reactants always go at the bottom. Therefore the E.N.Ramsden book was wrong and the Cambridge course book was right. I don't think that the Kc values for both these equations have a relationship with each other and they probably wouldn't ask you such a question so no need of worrying.

 

[Warrior66]

hey can someone help me out please , i need the answers for the end of chapter questions in the chemistry book , but i don't have the CD so how can I get the answers?

which book is it?

 

[strangerss]

It's made by Roger Norris ,Lawrie Ryan and David Acaster it's the chemistry coursework the newest edition i suppose .

 

[sweetiepie]

http://www.xtremepapers.com/community/threads/some-different-notes-website-are-available.10423/ notes r compiled here

 

[Ahmed Ali Akbar]

An mcq problem. Plz help

bond energy of C__I is lowest so compound in which it will be present will form precipitate very quickly..

 

[Warrior66]

It's made by Roger Norris ,Lawrie Ryan and David Acaster it's the chemistry coursework the newest edition i suppose .

oh i have that book...which end-of-chapter's answers do you want..i might be able to post them here hopefully..

 

[strangerss]

http://www.xtremepapers.com/community/threads/some-different-notes-website-are-available.10423/ notes r compiled here

hey thanks for your help but I got confused in where to download for free hehe.

 

[strangerss]

oh i have that book...which end-of-chapter's answers do you want..i might be able to post them here hopefully..

well , I want them all , but may be just equilibrium and states of matter if you can please? , although I'll understand if you can't.

 

[Warrior66]

well , I want them all , but may be just equilibrium and states of matter if you can please? , although I'll understand if you can't.

 

[Warrior66]

well , I want them all , but may be just equilibrium and states of matter if you can please? , although I'll understand if you can't.

 

[Warrior66]

An mcq problem. Plz help

Asalam-o-Alaikum!
well basically from my understanding, in option D there is an iodine which is not present in any other option and since in the periodic table, group 7, it is the lowest element i.e : F, Cl, Br, I therefore we know that the reactivity decreases as we down the group 7, and it forms the weakest bond, so very little energy is required to break the bond as compared to F, Cl and Br. And so it forms ions and these ions displace the nitrate from the silver nitrate to form silver iodide and this is shown by the yellow precipitate formed.

 

[TERMINATOR]

Asalam-o-Alaikum!
well basically from my understanding, in option D there is an iodine which is not present in any other option and since in the periodic table, group 7, it is the lowest element i.e : F, Cl, Br, I therefore we know that the reactivity decreases as we down the group 7, and it forms the weakest bond, so very little energy is required to break the bond as compared to F, Cl and Br. And so it forms ions and these ions displace the nitrate from the silver nitrate to form silver iodide and this is shown by the yellow precipitate formed.

JazaakAllahu khairan for making it so easy for me. Alhamdulillah.

 

[Warrior66]

JazaakAllahu khairan for making it so easy for me. Alhamdulillah.

Wa Iyyakum! Alhamdulillah! All praise and thanks to Allah the Exalted, the Lord of the universe.

 

[darknessinme]

Salaam. Any help with this mcq. .. it will be highly appreciated.

http://www.chemguide.co.uk/physical/basicrates/energyprofiles.html

Simple answer is that B is the only 1 step process. Others are 2 step.

 

[mamoon123]

Asalam alaikum.
Can anybody please tell me how we can solve question 38 and 40 in this paper (oct nov 2009)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w09_qp_12.pdf

Can you please tell me all the reactions that can occur using the same apparatus and the conditions required for the said reactions.

Also, can you tell me the oxidation number of Chlorine in all period 3 chlorides?

And can carboxylic acids react with 2,4-dintrophenylhydrazine?

I also have trouble with cis-trans isomers, can somebody please give pictorial references to the different isomers?

Lastly, what are Ziiger mier catalysts (I can't spell it right ) and which reaction do they catalyse?

Thanks ^_^
Btw, I manage to score 35/40 in MCQs and 51/60 in structured (I've only recently started practicing the past papers), am I safe? :x

 

[strangerss]

Thank you a lot , I really appreciate it , GOD bless you.

 

[aalmuhannadi]

In this question, I'm unsure of the products of each reaction as in the book it only details about when you have only one halogen attached to an alkene/alkane... What kind of reaction will happen with each answer? THis confused me because for example with NaOH, I'm not sure which of the carbon atoms the OH- ion attaches to. Do you classify this as an alkene or a halogenoalkene? And the syllabus doesn't say anything about halogenoalkenes... So how would you know how it would react with each one?

 

[aleezay]

View attachment 21026
In this question, I'm unsure of the products of each reaction as in the book it only details about when you have only one halogen attached to an alkene/alkane... What kind of reaction will happen with each answer? THis confused me because for example with NaOH, I'm not sure which of the carbon atoms the OH- ion attaches to. Do you classify this as an alkene or a halogenoalkene? And the syllabus doesn't say anything about halogenoalkenes... So how would you know how it would react with each one?

Wouldn't trichloromethane react with Br2.. the reaction would be somewhat similar to the addition reaction between alkenes and halogens.. except that this compound already is a halogenoalkene.. :/

 

[aleezay]

Q. 2.80g of a group II metal carbonate, XCO3, is added to 50cm^3 of 2.00 moldm^-3 HCl (excess) in a plastic cup. the temperature rose by 9.7K. Calculatre the Mr of the carbonate.

for this question, can we assume that q= sum of all the bond energies of bonds involved in the formula q=mcdT? I cant think of any other technique..

 

[mamoon123]

Q. 2.80g of a group II metal carbonate, XCO3, is added to 50cm^3 of 2.00 moldm^-3 HCl (excess) in a plastic cup. the temperature rose by 9.7K. Calculatre the Mr of the carbonate.

for this question, can we assume that q= sum of all the bond energies of bonds involved in the formula q=mcdT? I cant think of any other technique..

XCO3 + 2HCl ---> XCl2 + H2O + CO2
2.80g of XCO3 (ignore it for now)
x mol of XCO3 react with 2x mol of HCl
Moles of HCl = Volume(cm^3) multiplied by concentration(mol dm-3) DIVIDED by 1000
--> (50*2.00) / 1000
--> 0.1 mol

Compare the mole ratio.
If 2x = o.1 mol
then x = 0.05 mol

Now that you have the moles and the mass, find the Mr by using this:
Mr = mass/mol
--> 2.8/0.05
--> 56
Is this the correct answer?

Do forgive me if I wrote anything incorrect. Allah knows best.