Mass of 18F9: Solve with Q-value and Kinetic Energy Equations

[f4d_girl]

The reaction 18(number of neturons + protons) O(oxygen) 8 (number of protons) (p,n) 18 F 9

requires an input of energy equal to 2.453 MeV. What is the mass of 18F9?

I tried to use Q-value equation, but it didn't work out at all

then i thought, since the enrgy is conserved, the kinetic energy equation might work

but it didn't again

please help

 

[Astronuc]

So this is a binding energy type of problem.

¹⁸O + p -> ¹⁸F + n

And it requires an input of energy (endothermic) of 2.453MeV, in other words, the rest mass of the reactants is less than the rest mass of the products.

One could use an energy equivalent of the atomic mass unit (amu), and use amu's to solve the problem. Otherwise if the masses are in kg, and one uses mc², then energy would need to be in Joules.

If the formula for the Q value is written in the conventional way,

Q = (m_products - m_reactants) c² and Q < 0, for an endothermic reaction, and > 0 for exothermic reaction.

Try mass of ¹⁸O = 17.999161001 amu from http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?8,18

mass of ¹H = 1.00782503207 from http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?1,1

or mass p = 1.00727644 amu (Dolan, Fusion Research, 1982)

mass n = 1.00866491574 http://wwwndc.tokai.jaeri.go.jp/cgi-bin/nuclinfo2004?0,1

http://wwwndc.tokai.jaeri.go.jp/cgi-bin/selchart2004?Z=O&A=18

Mass-energy equivalence: 1 amu = 931.481 MeV, so 2.453MeV = 0.002633 amu.

And 1 eV = 1.60219 x 10^-19 J.