This is the question:
The vanadium in 50.0 cm3 of a 0.800 mol dm–3 solution of NH4VO3 reacts with 506 cm3 of sulfur(IV) oxide gas measured at 20.0 °C and 98.0 kPa.
Use this information to calculate the oxidation state of the vanadium in the solution after the reduction reaction with sulfur(IV) oxide.
Explain your working. The gas constant R=8.3 J K-1 mol-1 .
I've found the moles of V and the moles of SO2, but after that I'm stuck. the answer is +4. can someone please help and explain the steps too please!!