补充习题及答案-

2)1 mol of copper melting at 1200℃.Calculate (a )enthalpy change (b) entropy change and (c)Gibbs free energy change at this temperature.

DATA:

Θ

∆

Cu

m eltin g

H

,=3100 cal/mol, T metling,Cu=1083℃,

C p, l, Cu = 7.5 cal/mol ℃

C p, s, Cu = 5.41 + 1.5⨯10-3 T cal/mol ℃

Answers: (a) 3096.28 cal/mol (b) 2.284 cal/ (mol K) (c)-268.05(cal/mol)

3) two moles of a monatomic ideal gas are at contained at a pressure of 1 atm and temperature of 300K, 34.166j of heat are transferred to the gas as a result of which the gas expands and does 1216 joules of work against its surroundings. The process is reversible. Calculate the final temperature of the gas.

Answers: 252.5K

4) One mole of N2 gas is contained at 273 K and a pressure of 1 atm. The addition of 3000 joules of heat to the gas at constant pressure causes 832 joules of work to be done during the expansion*(. Calculate (a) the final state of the gas, (b) the value of △U and △H for the change of state. And (c) the values of C V for N2 . Assume that nitrogen behaves as an ideal gas. And that the above change of state is conducted reversibly.

Answers:a)P=1atm, T=373K, V=30.6L; b) △H=3000J, △U=2168J ; (c)C V= 2.5R

5) Ten moles of ideal gas, in the initial state P1=10 atm, T1 =300K, are taken round the following cycle:

a) a revisable change of state along a line path on the P-V diagram t the state

P=1atm T=300K

b) a reversible isobaric (constant pressure) compression to V=24.6 liters and

c) a reversible constant volume process to P=10 atm

how much work is done on or by the system during the cycle? Is this work done on the system or by the system?

Answers: 35KJ

8) one mole of monatomic ideal gas undergoes a reversible expansion at constant pressure during which the entropy of the gas increase by 14.4J/K, and the gas absorbs 6236 joules of heat. Calculate the initial and final temperatures of the gas. N mole of second monatomic ideal gas undergoes a reversible isothermal expansion during which it doubles its volume performs 1729 joules of work and increases its entropy by 5.763 J/K. Calculate N and the temperature at which the expansion was conducted.

Answers: 1) T0=300K, T=600K 2)N=1,T=300K

13) 5 moles of an ideal gas are contained adiabatically at 50atm pressure and 300K. The pressure is suddenly released to 10atm, and the gas undergoes an irreversible expansion during which it performs 4000 joules of work. Show that the final temperature of gas after the irreversible expansion is greater than that which the gas would attain if the expansion from 50 to 10atm had been conducted reversibly. Calculate the entropy produced as a result the irreversible expansion. The constant volume molar heat capacity of the gas C V has the value of 1.5R

Answers:T1=236K> T2=158K; 41.9J/K

14) the initial state of one mole of monatomic ideal gas is p=10atm and T=300K.Calculate the change in the entropy of the gas for (a) an isothermal decrease in the pressure to 5 atm (b) a reversible adiabatic decrease in the pressure to 5 atm (c) constant –volume decrease in the pressure to 5 atm Answers: (a)5.79J/K (b)0 (c)-8.64K/J