Work against the external pressure

[omni]

in the picture you can see the reaction.

it's known that 2 mol nitrogen reaction with 6 mol hydrogen gas to create ammonia.
what is the work against the external pressure in 1 Atm in 25 degrees Celsius?

i think i need to use this formula:W=-PexdeltaV.
but i can't know what is deltaV.

i just know that -Pex=-1atm. 1atm=101,325 Pa
and is a exothermic reaction.

how can i keep on from here?

thanks.

 

[Borek]

ΔV is just a volume change - what is an initial volume? What is a final volume?

 

[omni]

Is not given in the description question.
maybe i can use PV=nRT?
and from this formula i can find V?

what are you think?
and just to be sure W is what i need to find yes?

thanks.