Question

CHEMICAL THERMODYNAMICS! CLASS 11 A sample of gas present in a cylinder fitted with a frictionless piston expands against a constant pressure of 1atm from a volume of 2L to 12L. During the process it absorbs 600J of heat from the surroundings. Calculate the change in internal energy of the system.

Answer 1

Given:

• q= 600 J
• Initial volume= 2L
• Final Volume = 12L
• Pressure = 1atm

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Solution:

Change in volume:

= Vfinal- Vinitial

=12L - 2L

= 10L

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We know,

w= -P × Change in volume

=>w = -1 ×10 L-atm

=> w = -10 L- atm

Now 1 L-atm =101.3 J

w = -10× 101.3J

=> w = -1013 J

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According to first law of thermodynamics,

Change in energy = q+ w

=> Change in energy = 600 - 1013 J

=> Change in energy = $\bold{\red{-413 J}}$

Answer 2

W= -P. Change in volume

=-1×10 L. Atm

=-10 L. Atm

=-10×101.3 J

=-1013 J