Question

a gas present in a cylinder fitted with a frictionless piston expands against a constant pressure of 1 ATM from a volume of 2 litre to a volume of 6 litre in doing so it absorbs 800 joule heat from surroundings determine increase in internal energy of process

Answer 1

Hello friend,

Given-

Energy absorbed q = ΔH = 800 J

Initial volume V1 = 2L = 0.002 cu.m

Final volume V2 = 6L = 0.006 cu.m

Pressure P= 1 atm = 101325 Pa

Solution-

PΔV = 101325(0.006-0.002)

PΔV = 101325×0.004

PΔV = 405.3J

Enthalpy change is given by

ΔH = ΔU + PΔV

Rearranging equation,

ΔU = ΔH - PΔV

ΔU = 800-405.3

ΔU = 394.7 J

Change in internal energy will be 394.7 J.

Best luck for exams buddy...

Answer 2

Given:

Pressure = 1 atm

Volume at first = 2 l

Volume in the end = 6 l

Heat absorbed  = 800 J

To find:

The increase in internal energy of process.

Solution:

By law of thermodynamics,

Pressure Δ Volume = 1 (Change in volume)

Δ refers to the change

Converting 1 atm,

Pressure P= 1 atm = 101325 Pa

Liters into ml,

We get,

101325(0.006-0.002)

Pressure Δ Volume = 405.3J

To find the change in enthalpy,

Δ Energy = Δ Internal energy + Pressure ΔVolume

To find the change in internal energy,

ΔInternal energy = ΔEnergy - Pressure ΔVolume

ΔInternal energy = 800 - 405.3

The increase in internal energy will be 394.7 J