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Chemistry problem help - February 28th 2010, 10:58 AM

I've been given a question to do and I can not work out how to do it at all...so was wondering if someone could enlighten me please?

"The equations for the combination of gaseous atoms of carbon and hydrogen to form methane and ethane are shown below.
C (g) + 4H (g) --> CH4 (g) Enthalpy change = -1652KJmol-1
2C (g) + 6H (g) --> C2H4 (g) Enthalpy change = -2825KJmol-1

Use these data to calculate:
i. The bond enthalpy of a C-H bond
II. The bond enthalpy of a C=C bond"





   
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Re: Chemistry problem help - February 28th 2010, 07:19 PM

In the first equation, you have 4 C-H bonds yeah? Dividing the number by 4 (as you have four of them) I think will give you the answer for part one.

After you have worked it out for one C-H bond, you can work out how much energy from the second equation is the C-H bonds. 2825 - [ 6 x (energy of 1 C-H bond) ] ---- then stick a minus sign in front of it.

I think/hope that's right! If it doesn't make sense then just say and I'll try to explain it again.
Take care.
Anna
   
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