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Chem help..... :O

+3
Doc
Ahmed
The Banker
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Post by The Banker Thu Nov 19, 2009 6:50 pm

ok...
what is a dative covalent bond??
i've looked through all my books, asked my teachers... etc.
and didn't get a straight answer..
can u guyz help????
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Post by Ahmed Thu Nov 19, 2009 8:07 pm

Dative covalent bond is a description of covalent bonding between two atoms in which both electrons shared in the bond come from the same atom.
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Post by The Banker Thu Nov 19, 2009 8:16 pm

ohhhh
so one atom sharez its electronz with the other atom and the aother atom doesn't want to share its electronz??
like NH4????
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Post by Ahmed Thu Nov 19, 2009 8:22 pm

NH4+ is ionic...not covalent. It is an exception Wink. It acts like an ionic compound.
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Post by The Banker Thu Nov 19, 2009 8:29 pm

ahhhhhhhhhhhhh!!
i'm confuzzled man!
explain plz... Sad
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Post by Ahmed Thu Nov 19, 2009 8:32 pm

Covalent compounds usually have a negative net charge. NH4+ has a positive net charge. Therefore it acts as if it's a ionic compound (which have positive charges)

Covalent compounds are like:

SO4^-2
ClO3^-
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Post by The Banker Thu Nov 19, 2009 8:37 pm

kk
thanx ahmed...
ur a BIG help
Smile
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Post by Ahmed Thu Nov 19, 2009 8:38 pm

No Prob.

I have a chem test tomorrow :S

Make Du3aa for me PLEASE!!
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Post by The Banker Thu Nov 19, 2009 8:40 pm

kk
inshaAllah man..
Smile
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Post by Doc Sat Nov 21, 2009 4:37 am

so how was it?

insha'Allah you'll get an A

and a covalent bond is a bond between nonmetallic atoms where electrons are shared ...
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Post by Ahmed Sat Nov 21, 2009 2:20 pm

I am so happy, thank you all or you du3aas, I think they helped me a lot. I might have even gotten 100% Allahu A23lam, but I found it to be the test that I did the best on. Maybe beacause thsi time I actually studied lol? Razz
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Post by Egyptian Gazelle Sat Nov 21, 2009 2:48 pm

Sultan Ahmed IV wrote:I am so happy, thank you all or you du3aas, I think they helped me a lot. I might have even gotten 100% Allahu A23lam, but I found it to be the test that I did the best on. Maybe beacause thsi time I actually studied lol? Razz

WOW! Thats good l7l....I bet you got a 100 haha
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Post by Ahmed Sat Nov 21, 2009 4:52 pm

The Egyptian Gazelle wrote:
Sultan Ahmed IV wrote:I am so happy, thank you all or you du3aas, I think they helped me a lot. I might have even gotten 100% Allahu A23lam, but I found it to be the test that I did the best on. Maybe beacause thsi time I actually studied lol? Razz

WOW! Thats good l7l....I bet you got a 100 haha

Thanks Reem Razz
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Post by Egyptian Gazelle Sat Nov 21, 2009 4:52 pm

np
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Post by The Banker Sat Nov 21, 2009 8:28 pm

Sultan Ahmed IV wrote:I am so happy, thank you all or you du3aas, I think they helped me a lot. I might have even gotten 100% Allahu A23lam, but I found it to be the test that I did the best on. Maybe beacause thsi time I actually studied lol? Razz

alhamdullilah u found it easy man.... i actually made duaa 4 u..
now u have 2 make duaa 4 me coz i have a chem test on thursday... Very Happy
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Post by The Banker Sat Dec 19, 2009 5:28 pm

emm ok ppl i really need help :S

>> Q) Sodium burns in excess Oxygen to give the solid, Y.
a) Y contains 58.97% Sodium. Find the emperical formula.

this is how i worked it out..
100-58.97= 41.03
so there is 41.03% Oxygen in Y
Sodium: 58.97/23 =2.56 moles

Oxygen: 41.03/16 =2.56 moles
and so Sodium : Oxygen = 1:1
so the emperical formula is NaO
b) The relative molecular mass of Y is 78. What is the molecular formula?
Mr of NaO:: (23x1)+(16x1) = 39
78/39 =2
2(NaO)
= Na2O2
==================================================================
i have a feeling this is all wrong... i need someone to check it for me.
thanx
Smile
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Post by Steve Sat Dec 19, 2009 5:30 pm

the answer is always X = 2

its because burried treasure is always under a big 2 Smile
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Post by Ahmed Sat Dec 19, 2009 5:37 pm

Darn I did this like 2 months ago. Anyways...

Yes they are both correct.
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Post by The Banker Sat Dec 19, 2009 5:41 pm

Ahmed IV wrote:Darn I did this like 2 months ago. Anyways...

Yes they are both correct.
yh... i did this right at da begining of da year...
i'm revising 4 my real exam which is in 2 weeks :S
and i like ur new profile pic by da way... Wink


@Steve:: ahhh stop confusing me man!! Razz
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Post by Steve Sat Dec 19, 2009 5:42 pm

but ahmed said we were both correct Razz
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Post by Ahmed Sat Dec 19, 2009 5:43 pm

Well if you want to be 100% precise when dividing by the molar
mass of the Oxygen and Sodium you should divide by up to 4 sig figs.
The answer is still the same though. Wink

P.S.: Thanks, ii was my first profile, before any Y!A members were here...I missed it so I got it back Smile
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Post by The Banker Sat Dec 19, 2009 6:33 pm

Q)
a) what is the enthalpy chnage for the following reaction?
2C(graphite) +2H2 + O2 ========> CH3COOH

enthalpies of combustions:-
C = -394
H2 =-286
CH3COOH = -874

i'm totally baffed... ?!??!?! :S
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Post by Ahmed Sat Dec 19, 2009 6:35 pm

Simple:

[Enthalphy of Products]-[Enthalphy of Reactants]

But wait, why does C and H2 have an enthalpy?? Could you give me their states? (solid,liquid, gas)
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Post by The Banker Sat Dec 19, 2009 6:37 pm

C is solid
H is gas
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Post by Ahmed Sat Dec 19, 2009 6:41 pm

Those values are the enthalpies of formation, correct?
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