Heat of Atomization Ethane: Wavelength to Break C-C Bond

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Discussion Overview

The discussion revolves around calculating the wavelength of light required to break the C-C bond in ethane, using the heat of atomization values for methane and ethane. Participants explore the types of bonds present in these molecules and the energy associated with breaking them.

Discussion Character

  • Homework-related
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant states that the heat of atomization for methane is 360 kJ/mol and for ethane is 620 kJ/mol, questioning the relevance of methane's energy in the context of breaking the C-C bond in ethane.
  • Another participant asks about the types of bonds present in the molecules, leading to clarification that methane (CH4) contains only C-H bonds, while ethane (C2H6) contains both C-C and C-H bonds.
  • It is noted that bond energy does not significantly depend on the molecule, suggesting that the energy values can be used for calculations across different molecules.
  • Participants calculate the energy required to break C-H bonds in methane and ethane, concluding that breaking 4 C-H bonds requires 360 kJ, leading to a value of 90 kJ per C-H bond.
  • One participant proposes that since ethane's heat of atomization is 620 kJ, the energy for the C-C bond can be derived from the total energy required to break all bonds in ethane.
  • Another participant confirms the calculations and suggests that the energy for the C-C bond can be inferred from the differences in total energy required for breaking the bonds in ethane.

Areas of Agreement / Disagreement

Participants generally agree on the types of bonds present in methane and ethane and the calculations related to bond energies. However, there is no consensus on the exact approach to determine the energy of the C-C bond, as some participants question the relevance of methane's energy and the calculations involved.

Contextual Notes

The discussion includes assumptions about bond energy uniformity and does not resolve the specific calculations for the C-C bond energy, leaving some steps and dependencies on definitions unresolved.

Raghav Gupta
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Homework Statement


The heat of atomization of methane and ethane are 360kJ/moo and 620kJ/mol, respectively.
The longest wavelength of light capable of breaking the C-C bond is (Avogadro number = 6.02 x 1023, h= 6.62 x 1034J s

Homework Equations


E = hν = hc/λ

The Attempt at a Solution


I think we should consider energy of ethane only as it only has C-C bond.
What is the use of methane energy?
 
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What bonds are present?
 
methane is CH4 and ethane is C2H6. All are single bonds.
 
Let me rephrase the question: bonds between what atoms are present?
 
Bonds between carbon and hydrogen are present in methane and in ethane between carbon and carbon and also carbon and hydrogen.
 
So you have two kinds of bonds. Methane contains only one kind, ethane contains two kinds. Within a good approximation bond energy doesn't depend on the molecule.
 
So now what should I do?
Take E = 360 kJ/mol ?
 
360 kJ/mol is required to break how many bonds between which atoms? How much per this particular kind of bond is it?
 
To break 4 C-H bond we require 360 kJ. For 1 C-H bond it is 90 kJ.
For 6 C-H it is 540 kJ.
So for ethane, heat of atomization is 620 kJ.
So for C-C bond it is 90 kJ/ mol
For 1 C-C bond it is 90 / (6.02 x 1023) kJ
 
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  • #10
Hi!
4 (C-H) bonds require 360kJ/mol...to break them
1×C-C bond+6(C-H) bonds require 620 KJ/mol.
So you can find C-C bond energy.
 
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  • #11
Thanks all of you, got it.
Mooncrater I think we had written the posts at same time, so you don't realized my 9th post?
 
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  • #12
Yup...you're absolutely right..heehee tech sometimes messes things up:)
 
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