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

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SUMMARY

The heat of atomization for methane is 360 kJ/mol and for ethane is 620 kJ/mol. The longest wavelength of light capable of breaking the C-C bond in ethane can be calculated using the equation E = hν = hc/λ, where h is Planck's constant (6.62 x 10^-34 J s) and Avogadro's number is 6.02 x 10^23. The energy required to break one C-C bond is determined to be 90 kJ/mol, derived from the total heat of atomization of ethane and the known bond energies of C-H bonds.

PREREQUISITES
  • Understanding of bond energies, specifically C-C and C-H bonds
  • Familiarity with the concept of heat of atomization
  • Knowledge of Planck's equation for energy calculations
  • Basic understanding of Avogadro's number and its applications
NEXT STEPS
  • Research the calculation of bond energies using experimental data
  • Learn about the implications of bond energies in chemical reactions
  • Study the relationship between wavelength and energy in photochemistry
  • Explore advanced topics in thermochemistry related to heat of formation
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Chemistry students, educators, and professionals interested in thermodynamics and molecular bonding, particularly those focusing on organic compounds like methane and ethane.

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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