# calculating work done

#### inaccensa

10+ Year Member
Work done by/on the gas is given by W= PdeltaV

Which of the
following gas properties is needed to

calculate
the work done by an expanding gas?

I.
The initial and final pressures
II
. The initial and final volumes

III.
The path followed during the expansion,

A.
I only

B.
Il only

C.
I and Il only

D. I,II, and III----------- correct ans

I know that work is not a state function,but based on the formula, there is no need to determine the path of the gas. I guess if it were a graph-based q, I would need the path. Can anyone please shed some light.

Thanks

#### wanderer

10+ Year Member
5+ Year Member
Work done by/on the gas is given by W= PdeltaV

Which of the
following gas properties is needed to

calculate
the work done by an expanding gas?

I.
The initial and final pressures
II
. The initial and final volumes

III.
The path followed during the expansion,

A.
I only

B.
Il only

C.
I and Il only

D. I,II, and III----------- correct ans

I know that work is not a state function,but based on the formula, there is no need to determine the path of the gas. I guess if it were a graph-based q, I would need the path. Can anyone please shed some light.

Thanks
The formula only applies to an isobaric process, hence the need to know the path. Other processes, like adiabatic and isothermal, have different equations.

Last edited:

#### ezsanche

10+ Year Member
5+ Year Member
you knew that work is a path function and you knew that it depends on the change of volume. so you know the answer is D.

OP

#### inaccensa

10+ Year Member
The formula only applies to an isobaric process, hence the need to know the path. Other processes, like adiabatic and isothermal, have different equations.
thanks. Wt r the other formulae

#### wanderer

10+ Year Member
5+ Year Member
thanks. Wt r the other formulae
I don't remember exactly. For adiabatic W=dU, so it's something like n*c*dT
for isothermal W=-Q, and P=nRT/V so if you integrate the function you get something along the lines of W = nRT ln Vf/Vi