Part 1: 1 mole of an ideal gas is at 6 atm pressure, occupies 7 L and has an int
ID: 2208550 • Letter: P
Question
Part 1: 1 mole of an ideal gas is at 6 atm pressure, occupies 7 L and has an internal energy of 672 J. The gas is first cooled at constant volume until its pressure is 2 atm. It is then allowed to expand at constant pressure until its volume is 8 L with an internal energy of 1450.5 J. Calculate the work done by the gas. Answer in units of J.
Part 2: Find the heat added during this process. Answer in units of J
Please show me steps to this question so I can see what I'm doing wrong. Thanks
Explanation / Answer
Work = P * DeltaV PV = nRT Work = nRT P?V is definitely not equal to PV! The work done by the gas in an infinitesimal step is equal to the pressure multiplied by the change in volume. The equation Work=P?V is true only for constant pressure; for general cases, we have to employ the integral Work=?PdV Thus, the only part of the problem where work is done is when the pressure is held constant and the volume expands. p => 7 atm x (101300 pascal) = 709100 pascal (pascal is metric units of N/m^2) ?V => 8L - 3 L = 5 L (1 m^3 / 1000 L) = 0.005 m^3 (again, we use metric units) W = p?V = 709100 N/m^2 (0.005 m^3) = 3546 N m = 3546 J