Question

What is the change in the internal energy of the system when 1.243 mol of NH 3(g) is formed from N 2(g) and H 2(g) at 25 degrees C and 1.0 atm?

Answer 1

N2 + 3H2 ==> 2NH3

delta E = q + w

I would look up delta H^o_f. Then
dHrxn = (n*dHoproducts) - (n*dHoreactants) and that will give you q.
W is -p*delta V.
Use PV = nRT. You know n, R, P, and T; solve for V at the end. Knowing mols formed you can calculate mols N2 and H2 initially and calculate V initially.