In: Chemistry
2.60 moles of an ideal gas with CV,m=3R/2 undergoes the transformations described in the following list from an initial state described by T = 310. K and P = 1.00 bar.
Calculate:
A. The gas is heated to 710 K at a constant external pressure of 1.00 bar. Calculate q for this process.
B. The gas is heated to 710 K at a constant external pressure of 1.00 bar. Calculate w for this process.
C. The gas is heated to 710 K at a constant external pressure of 1.00 bar. Calculate ΔU for this process..
D. The gas is heated to 710 K at a constant external pressure of 1.00 bar. Calculate ΔH for this process.
E. The gas is heated to 710 K at a constant external pressure of 1.00 bar. Calculate ΔS for this process.
F. The gas is heated to 710 K at a constant volume corresponding to the initial volume. Calculate q for this process.
G. The gas is heated to 710 K at a constant volume corresponding to the initial volume. Calculate w for this process.
H. The gas is heated to 710 K at a constant volume corresponding to the initial volume. Calculate ΔU for this process.
I. The gas is heated to 710 K at a constant volume corresponding to the initial volume. Calculate ΔH for this process.
J. The gas is heated to 710 K at a constant volume corresponding to the initial volume. Calculate ΔS for this process.
K. The gas undergoes a reversible isothermal expansion at 310. K until the pressure is one third of its initial value. Calculate q for this process.
L. The gas undergoes a reversible isothermal expansion at 310. K until the pressure is one third of its initial value. Calculate w for this process.
M. The gas undergoes a reversible isothermal expansion at 310. K until the pressure is one third of its initial value. Calculate ΔU for this process..
N. The gas undergoes a reversible isothermal expansion at 310. K until the pressure is one third of its initial value. Calculate ΔH for this process.
O. The gas undergoes a reversible isothermal expansion at 310. K until the pressure is one third of its initial value. Calculate ΔS for this process.
Thank you
We are given moles n = 2.6 moles
constant volume heat capacity Cv = 3R/2
Temperature T = 310 K
P = 1 bar = 0.987 atm
so, volume V = nRT/P (By ideal gas equation PV = nRT, R is gas constant , R = 0.0821 L atm/mole-K)
so, V = 2.6 moles * 0.0821 L atm /mole-K * 310 K / 0.987 atm
V = 67.044 L
So, inital volume is 67.044 L
If we increase the temperature to 710 K at constant pressure of 1 bar the volume will change as volume will be directly proportional to T if moles n and pressure P is constant.
so, Vi/Vf = Ti/Tf where subscripts i and f denote the initial and final values of volume and temperature.
so, 67.044 L/Vf = 310 K / 710 K
so, Vf = 67.044 * 710/310 L = 153.55 L
So, final volume is 153.55 L
b)
workdone w for this transformation can be calculated as
w = -PextV where Pext is the external pressure P = 0.987 atm, V = change in volume
= Vf - Vi = 153.55 L - 67.044 L = 86.506 L
so, w = -0.987 atm * 86.506 L = -85.381 L atm
As 1 L atm = 101.33 J
w = -85.381 * 101.33 J = -8651.657 J
c)
Change in internal energy U = nCvT
T = 710 K- 310 K = 400 K
n = 2.6 moles
Cv = 3R/2, R = 8.314 J/mole-K
so, U = 2.6 moles * (3/2)*8.314 J/mole-K * 400 K
= 12969.84 J
a)
By first law of thermodynamics we have
U = q + w
Where q is the heat exchanged during the process.
Putting values of U and w we get -
12969.84 J = q -8651.657 J
q = 21621.497 J
d)
Change in enthalpy of the transformation H is given as -
H = U + PV
Also, PV = -w = 8651.657 J
and U = 12969.84 J
so, H = 12969.84 J + 8651.657 J
= 21621.497 J