Energy to dissociate an H2 molecule from formation enthalpy

[pentazoid]

Homework Statement

Look up the enthalpy of formation of atomic hydrogen in the back of the book. This is the enthalpy change when a mole of atomic hydrogen is formed by dissociating 1/2 mole of molecular hydrogen (the more stable state of the element). From this number, determinethe energy needed to dissociate a single H2 molecule , in electron-volts.

Homework Equations

PV=3100 J
delta(H)=delta(U)+P*delta(V)
H=U+PV

The Attempt at a Solution

find delta(U)
delta(U)=delta(H)-P*delta(V)

found delta(H) to be delta(H)=-217.97 kJ

According to the standard table T=298 K and P=1 bar=1atm?
R=8.31 J/K

PV=RT=(8.31 J/K)(298 K)=2.5 kJ

H-PV=(-217.97 kJ)-(2.5 kJ)=-220.5 kJ

Did I find delta(U) correctly?

 

[TeethWhitener]

This is the enthalpy of formation of atomic hydrogen, so the answer needs to be doubled (then the units changed to eV).