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JEE MainChemistryThermodynamics (C)

An ideal gas undergoes isothermal compression against a constant external pressure of 4 atm . During this process, the gas releases 200 L atm of heat. If the final volume of the gas is 10 L , the initial volume of the gas is ______ L .

Correct answer

60

Step-by-step solution

For an isothermal process involving an ideal gas, the change in internal energy is zero ( U = 0 ). From the first law of thermodynamics: U = Q + W W = -Q Since heat is released by the gas, Q = -200 L atm . Therefore, work done on the gas is W = +200 L atm . For compression against a constant external pressure, the work done is given by: W = -P_ ext (V_f - V_i) Substituting the given values: 200 = -4(10 - V_i) -50 = 10 - V_i V_i = 60 L Answer: 60

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