Question

a gas contained in a cylinder fitted with the frictionless Piston expands against a constant external pressure of 1 ATM from a volume of five litre to a volume of 10 litres in doing so it absorbs 400J of thermal energy from its surroundings determine the change in internal energy of system​

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.