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last SG · 2015-08-19T22:54:00+00:00

Topic : atomic radius Hi! This is from singapore cambridge nov a level exam year 2010,Paper 1 qn 1Qn: which element has the largest atomic radius?BrKKrScSo...

Flying grenade SG

Obviously.

I SEE , TY ULTIMA for reply

UltimaOnline SG

A level p3 qn 1C

i calculated D.O.U. of C10H16 is 3. what can i do with this info?

thanks ultima

U coconaden. Can u spot what's wrong with what you wrote above? As for what u can do with it, what do u think? If u have no idea how to use d.o.u, then don't bother using it. Go ask ur school teacher or private tutor.

Flying grenade SG

D.O.U. of 1 double bond is 1 right

i calculated D.O.U. for the above molecule =3

but the molecule only have 2 double bond ! T-T help ultima

UltimaOnline SG

D.O.U. of 1 double bond is 1 right

i calculated D.O.U. for the above molecule =3

but the molecule only have 2 double bond ! T-T help ultima

U coconaden. First, spot what's wrong with ur original post.

Flying grenade SG

U coconaden. First, spot what's wrong with ur original post.

damn. sorry. ok corrected roflmao

Flying grenade SG

spot the difference spot the mistake is fun

UltimaOnline SG

D.O.U. of 1 double bond is 1 right

i calculated D.O.U. for the above molecule =3

but the molecule only have 2 double bond ! T-T help ultima

Eh u (still a) coconaden lah! Ask yourself, why exactly does benzene ring have 4 d.o.u??? Or u dunno and just blindly memorized that fact?!? Once u can answer that qn, u can answer ur own qn, about why molecules A, B and C have 3 d.o.u each.

Flying grenade SG

i worked out d.o.u. of benzene =4 .

D.O.U.(benzene) = (14-6)/2 =4

Flying grenade SG

i worked ouuuuuuttttt for that molecular formula for A,B,C have 3 d.o.u. ,

my qn

is one double bond = 1 d.o.u.?

cos all of A,B,C have only 2 double bonds in their structural formula

how/in what way can use dou to write out deductions?

teach me plsss

Flying grenade SG

i dont want write C and H have comparable number of H atoms or ratio C/H is approx one or not approx one

e.g. 16H , 10 C. is 1.6 approx one? is 1.4 approx one? is 1.2 approx one? is 14H atoms and 10 C atoms comparable in number?

UltimaOnline SG

i worked out d.o.u. of benzene =4 .

D.O.U.(benzene) = (14-6)/2 =4

Look at the *structure* (not the Singapore JC guniang-sissy version with the circle in the middle, ie. resonance hybrid ; but use the Uni level garang-gungho version with alternating double and single bonds, ie. resonance contributor) of benzene, and explain exactly why the d.o.u. for each benzene ring is 4.

Flying grenade SG

to explain why d.o.u. of benzene is 4, isn't the evidence/reason my calculation workings?

Flying grenade SG

hmm, if use words and explain, is it becos the index of hydrogen deficiency of benzene is four??

Flying grenade SG

anyway im more stress abt this qn now : for the A level 2015 p3 qn 1 question, we calculated dou is 3. but the molecule only gt 2 double bonds. one double bond = 1 dou

what shld i do?? what shld i learn from 3 dou? teach me ultima T-T

UltimaOnline SG

anyway im more stress abt this qn now : for the A level 2015 p3 qn 1 question, we calculated dou is 3. but the molecule only gt 2 double bonds. one double bond = 1 dou

what shld i do?? what shld i learn from 3 dou? teach me ultima T-T

Figure this out yourself. What's the definition of D.O.U.???

Super Coconaden Hint for Super Coconaden pple : obviously it can't be just double bonds which affect degree of unsaturation!!! *Sheeeesh

Flying grenade SG

eh so what is your correct explanation of why dou of b.ring is 4?? have other explanations other than the mathematical calculation?

share other explanations too please !

Flying grenade SG

ok yes, right. not only double bonds affect dou

a cyclic ring formed by 6 C atoms is one dou unit is it?

then what's the beauty/usefulness of dou?

to check >4 or <4 only?

or is it like for me to narrow down guesses, maybe like, the molecule could probably have two double bonds, and one ring made up of 6 C atoms?

UltimaOnline SG

ok yes, right. not only double bonds affect dou

a cyclic ring formed by 6 C atoms is one dou unit is it?

then what's the beauty/usefulness of dou?

to check >4 or <4 only?

or is it like for me to narrow down guesses, maybe like, the molecule could probably have two double bonds, and one ring made up of 6 C atoms?

So what's the *definition* of D.O.U? Why must the ring consist of 6 C atoms?

Flying grenade SG

exactly la sia. ring need not be formed by 6 C atoms only. THEN HOW SIAAA. ring how?? T_T how to handle rings , when we dk how many C atoms in rings??

Flying grenade SG

is the definition of dou index of hydrogen deficiency? how many H atoms the molecule is deficient , from the theoretical saturated form?

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