When 0.5 mole of a gas expands isothermally and reversible from a volu...
Introduction:
The problem involves calculating the change in internal energy of a gas which expands isothermally and reversibly from a volume of 2L to 5L at 300K. The amount of heat absorbed during the process is given as 200 cal.
Formula:
The change in internal energy (ΔU) of a gas is given by the formula:
ΔU = q + w
where q is the heat absorbed by the system and w is the work done by the system. For an isothermal and reversible expansion, the work done by the system is given by:
w = -nRT ln(Vf/Vi)
where n is the number of moles of gas, R is the gas constant, T is the temperature in Kelvin, Vf is the final volume and Vi is the initial volume.
Calculation:
Given,
n = 0.5 mole
Vi = 2L
Vf = 5L
T = 300K
q = 200 cal
Using the formula for work done, we get:
w = -nRT ln(Vf/Vi)
w = -0.5 * 8.314 * 300 * ln(5/2)
w = -623.34 J
Converting the heat absorbed from calories to Joules, we get:
q = 200 * 4.184
q = 836.8 J
Substituting the values of q and w in the formula for change in internal energy, we get:
ΔU = q + w
ΔU = 836.8 - 623.34
ΔU = 213.46 J
Therefore, the change in internal energy of the gas is 213.46 J.
Conclusion:
The change in internal energy of a gas which expands isothermally and reversibly from a volume of 2L to 5L at 300K, absorbing 200 cal of heat is 213.46 J.