Work done by isothermal expansion of reaction vessel (changing moles)?

sparkle123

Temperature 298K, Original Volume 1L
Reaction: 3A-->5B
0.0627 mol of A originally --> Pi=1 atm
0.1044 mol of B finally --->Pf=2.55 atm

I don't think you can simply use w=-nRTln(Pi/Pf) because number of moles is changing here.
How would you solve this?