Derive the expression for work done by a gas during an isobaric process (constant pressure).

(N/A) Consider a gas enclosed in a cylinder fitted with a frictionless,movable piston of cross-sectional area $A$. When the gas expands at constant pressure $P$,the piston moves outward by a small distance $\Delta x$.
The force exerted by the gas on the piston is $F = P \times A$.
The work done by the gas during this small displacement $\Delta x$ is:
$\Delta W = F \times \Delta x = (P \times A) \times \Delta x$
Since the change in volume is $\Delta V = A \times \Delta x$,we can write:
$\Delta W = P \Delta V$
For a finite change in volume from $V_i$ to $V_f$ at constant pressure $P$,the total work done is:
$W = \int_{V_i}^{V_f} P \, dV = P(V_f - V_i) = P \Delta V$
According to the first law of thermodynamics,$\Delta Q = \Delta U + W$. Substituting the expression for work,we get:
$\Delta Q = \Delta U + P \Delta V$