Energy Change Nuclear Chemistry

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Discussion Overview

The discussion revolves around calculating the energy change (delta E) during a nuclear reaction involving thorium-229. Participants are attempting to determine how to incorporate a mass input of 500 grams into the energy change calculation, specifically using the mass defect and the relationship between mass and energy.

Discussion Character

  • Homework-related

Main Points Raised

  • One participant presents the nuclear reaction and the relevant masses, indicating a known answer for delta E.
  • Another participant questions how to incorporate the mass of 500 grams into the solution, expressing uncertainty about the calculation process.
  • A participant calculates the number of moles of thorium based on the given mass and molar mass.
  • There is a request for further assistance in progressing the calculation after determining the number of moles.
  • Participants discuss the concept of mass defect, with one suggesting a value and another challenging its correctness.
  • There is confusion regarding how to relate the calculated moles of thorium to the mass defect in the energy change calculation.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to proceed with the calculation, and there are differing views on the mass defect value and its implications for the energy change.

Contextual Notes

Participants express uncertainty about the correct application of the mass defect in relation to the number of moles calculated, indicating potential gaps in understanding the relationship between mass, energy, and nuclear reactions.

NY152
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Homework Statement


Determine the energy change, delta E, in J when 500 g of 229/90 Th undergoes the following nuclear reaction:
229/90 Th --> 225/88 Ra + 4/2 He
The nuclear masses in amu or g/mol are: Th-229: 229.03175; Ra-225: 225.02360; He-4: 4.00260

Homework Equations


delta E = deltam(c)^2
c= 3*10^8
1 g= 6.02*10^23

The Attempt at a Solution


I know how to do a problem like this without a different mass input, but I have no idea how to incorporate the 500 grams into the solution. The answer is -1.09*10^12 J
 
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NY152 said:

Homework Statement


Determine the energy change, delta E, in J when 500 g of 229/90 Th undergoes the following nuclear reaction:
229/90 Th --> 225/88 Ra + 4/2 He
The nuclear masses in amu or g/mol are: Th-229: 229.03175; Ra-225: 225.02360; He-4: 4.00260

Homework Equations


delta E = deltam(c)^2
c= 3*10^8
1 g= 6.02*10^23

The Attempt at a Solution


I know how to do a problem like this without a different mass input, but I have no idea how to incorporate the 500 grams into the solution. The answer is -1.09*10^12 J
Step at a time: how many mol?
 
Bystander said:
Step at a time: how many mol?
Would you do 500 g Th * 1 mol Th/229.03175 g Th = 2.183 mol Th
 
Yes. Can you take it the rest of the way?
 
Bystander said:
Yes. Can you take it the rest of the way?
Well I don't really know what to do with that number now. How do I incorporate it into the change in mass?
 
NY152 said:
g/mol are: Th-229: 229.03175; Ra-225: 225.02360; He-4: 4.00260
229 = 225 + 4; what is the mass defect?
 
Bystander said:
229 = 225 + 4; what is the mass defect?
The mass defect would be around -4, but so then how do you incorporate the 2.183 mol of Th??
 
NY152 said:
The mass defect would be around -4
"WORNG!" Try again, please.
 

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