internal energy, solution provided

[FATIMA]

calculate the change in internal energy for the following reaction at 1.00 atm and 25 degrees celcius

2 CO(g) + O₂(g) = 2 CO₂(g) deltaH = -566.0KJ

U = q + w or U = q - P*deltaV

what i did was
1) find q first using q=deltaH*n = (-566KJ)(2mol) = -1132/2 since this is for 2 moles and i get 566KJ/mol
2) find the change in volume using PV = nRT, isolate v and got 48.931L
3) use U = q - P*deltaV and solved for U and i got 517.069KJ, but the answer is -563.5KJ

What am i doing wrong?