Question

1 kg air in a piston-cylinder assembly is heated at constant pressure, resulting the expansion of the volume. the initial temperature of the air was 300 k, and the air temperature becomes 500 k after the expansion. what is the boundary work done by the air

Answer 1

Answer:

57,42 KJ

Explanation:

By a isobaric proces, the expresion for the works in the jpg adjunt. Then:

W = Pa(Vb - Va) = Pa*Vb - Pa*Va ---(1)

By the ideal gases law: PV=RTn

Then, in (1): (remember Pa = Pb)

W =  R*Tb*n - R*T*an = R*n*(Tb - Ta) --- (2)

Since we have 1 Kg air: How much is this in moles?

From bibliography: 28.96 g/mol

Then, in 1 Kg (1000 g) there are:

n =  34,53 mol

Finally, in (2):

W =  (8,3144 J/K.mol)*(34,53 mol)*(500K - 300K) = 51 419,9 J ≈ 57,42 KJ