MCQEasyJEE 2026Internal Energy & Enthalpy

JEE Chemistry 2026 Question with Solution

Which of the following graphs between pressure pp versus volume VV represents the maximum work done?

  • A
    Pressure-volume graph with pressure marked up to 2.0 bar and volume up to 22.4 L, showing a rectangular path with vertical line at 22.4 L and arrows indicating cyclic motion.
  • B
    Pressure-volume graph from 22.4 L to 44.8 L with pressure from 2.0 bar to 1.0 bar, showing a curved expansion path and a horizontal return path forming a cycle.
  • C
    Pressure-volume graph between 22.4 L and 44.8 L and pressures 2.0 bar to 1.0 bar, showing two curved paths joining the same endpoints and enclosing a lens-shaped cycle.
  • D
    Pressure-volume graph showing expansion from 22.4 L, 2.0 bar to 44.8 L, 1.0 bar along a decreasing curve, with area under the curve extending to the volume axis.

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: We must identify which pp-VV graph represents the maximum work done.

Find: The correct option corresponding to the largest work.

For a process, work done is given by

W=PdVW = \int P \, dV

So, the magnitude of work is equal to the area under the PP-VV curve. For a cycle, work is the enclosed area.

From the given graphs:

  1. Graph 1 has zero enclosed or effective area for work.
  2. Graphs 2 and 3 are cyclic paths enclosing comparatively smaller areas.
  3. Graph 4 shows expansion from VV to 2V2V with pressure decreasing, and the area under this curve down to the volume axis is the largest.

Therefore, the graph representing the maximum work done is Graph 4.

The correct option is D.

Common mistakes

  • Confusing work done in a cycle with work done in an open expansion process. For a cycle, work is the enclosed area, but for an expansion process it is the area under the curve. Always identify the type of process first.

  • Looking only at the shape of the curve and not at the actual area. A more complex-looking graph does not imply larger work; compare the area represented on the pp-VV diagram.

  • Ignoring the volume interval. Work depends on PdV\int P \, dV, so both pressure and the change in volume matter. A graph spanning a larger volume range can produce greater work.

Practice more Internal Energy & Enthalpy questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Related questions