An ideal monatomic gas with its isobaric expansion was reported to have a heat quantity of 1000J. What work is done with gas?

Isobaric expansion is constant pressure expansion.

The formula for heat in this case:
A ‘= P * ΔV
ΔU = i / 2 + vRΔT

i for a monatomic gas is equal to 3, therefore:
ΔU = 3/2 + vRΔT

Let us write the equation 1 of the thermodynamics:
Q = A ‘+ ΔU

Let’s substitute:
Q = A ‘+ 1/2 (A’) = A ‘+ 3/2 (A’)
Then
A ‘= ΔQ / 2.5 = 400 (J)