# Energy Change Nuclear Chemistry

NY152

## 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

Homework Helper
Gold Member

## 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?

NY152
Step at a time: how many mol?
Would you do 500 g Th * 1 mol Th/229.03175 g Th = 2.183 mol Th

Homework Helper
Gold Member
Yes. Can you take it the rest of the way?

NY152
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?

Homework Helper
Gold Member
g/mol are: Th-229: 229.03175; Ra-225: 225.02360; He-4: 4.00260
229 = 225 + 4; what is the mass defect?

NY152
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??