Chemistry: Post your doubts here!

[♣♠ Magnanimous ♣♠]

Sorry for being late even though you( Lucy Black )got it
I will show you my way maybe it will be easier

ii) General formula of ALCOHOLS CnH(2n+1) OH, as magnanimous stated.
We know the ratio of masses C:H:OH will be 12n:1(2n+1):1*(16+1) from the general formula and they should equate to 116.
The 12,1 and (16+1) are the relative atomic masses
12n+2n+1+17=116
14n=98
n=98/14
n=7

Now just replace the n with 7 in the formula
C7H15OH

Nic method
Thanks

 

[Lucy Black]

How?

Magnanimous...used d same method...

 

[ZaqZainab]

Magnanimous...used d same method...

did he? if he did he would have ended up with he same answer as mine.

 

[♣♠ Magnanimous ♣♠]

Magnanimous...used d same method...

did he? if he did he would have ended up with he same answer as mine.

Actually the thing is ki my maths is poor a looooooot!

 

[Lucy Black]

did he? if he did he would have ended up with he same answer as mine.

i meant to say i used d same method...

 

[ayaman Azmi]

Can anyone post a link for the Cambridge As and A Level Chemistry textbook or at least point me to a thread that does? Thanks in advance

 

[♣♠ Magnanimous ♣♠]

Can anyone post a link for the Cambridge As and A Level Chemistry textbook or at least point me to a thread that does? Thanks in advance

Do you wanna buy it?
Actually I have soft copy of chem coursebook but i cannot upload it due to some errors here than too i will try again and let you know by tagging

 

[MarcoReus]

Is the second edition of the Cambridge endorsed Chemistry textbook (authors are Dawnie, Norris, David Acaster and maybe someone else) released yet?

Remember, SECOND EDITION - printed 2014, specifically for the new syllabus.

 

[asadalam]

Is the second edition of the Cambridge endorsed Chemistry textbook (authors are Dawnie, Norris, David Acaster and maybe someone else) released yet?

Remember, SECOND EDITION - printed 2014, specifically for the new syllabus.

Its available online i think,not in shops afaik.

 

[MarcoReus]

Its available online i think,not in shops afaik.

And where do I get it online?

 

[asadalam]

And where do I get it online?

http://www.amazon.com/Cambridge-Int...emistry-(second-edition)#sthash.ulQ8Cq62.dpuf

 

[david1210]

One question..
Explain why the enthalpy change of formation for water is identical to the standard enthalpy change of combustion of hydrogen?

 

[Educationist]

does anyone have topic wise pastpapers for chemistry ??? pls reply .....

 

[Shadow]

Guys can anybody give me a link or a file for topical Chem past papers of p4? I am looking for past paper questions for Kinetics... Please post it asap here

 

[david1210]

Need help for P11 , 12 and 13 May/June 2013. Do you have any links for this papers' solutions?

 

[♣♠ Magnanimous ♣♠]

does anyone have topic wise pastpapers for chemistry ??? pls reply .....

Guys can anybody give me a link or a file for topical Chem past papers of p4? I am looking for past paper questions for Kinetics... Please post it asap here

https://www.xtremepapers.com/community/threads/as-chemistry-topical-finally-here.23520/

Shadow it has link which contains A level Topicals for Paper 4 and may be paper 5 too

 

[Metanoia]

One question..
Explain why the enthalpy change of formation for water is identical to the standard enthalpy change of combustion of hydrogen?

Writing out the equations for both of them based on the definitions, we can see that they are the same.

H2(g) + 1/2 O2(g) --> H2O (l)

 

[Metanoia]

What's the reason for Sodium and group 1 elements having a low melting point?

Doesn't answer her question.

princess Anu:

If by any chance you don't get what I have just wrote, then here is a simpler explanation

As we go down the group, the size of the atoms increases right? Thus the outer valence electron goes farther away from the nucleus (the nucleus is at the center). Metallic bonding involves the attraction between the valence of electrons and the nucleus. Since the valence electrons are farther away, there will be less attraction between the nucleus and the electrons. Kinda like a magnet and a strip of iron. The farther you take the strip from the magnet, the weaker the attraction. Since the attraction is weaker, less energy is required to overcome the forces of attraction.

The suggested answer, while conceptually correct, has not answered the question totally.

It's more of explaining why the melting point of Group I metals decreases down the group rather than why Group I metals on the whole has a low melting point.

To answer the second point, we need to bring in the fact that strength of metallic bonds are proportional to the number of delocalised electrons, and that Group I metals will only provide one electron per atom.

In summary, strength of metallic bond is directly proportional to delocalised electrons and indirectly proportion to atomic radii.

 

[yousef]

could someone help me with may june 2014 paper
varient 23 , question 1 b(iii)
http://www.gceguide.com/search/label/AS & A Level : Chemistry (9701)

 

[Shadow]

https://www.xtremepapers.com/community/threads/as-chemistry-topical-finally-here.23520/

Shadow it has link which contains A level Topicals for Paper 4 and may be paper 5 too

Heyy thanks alot buddy!