3, working with standard values (Appendix C of text): (a) Appendix c lists the s

ID: 1036787 • Letter: 3

Question

3, working with standard values (Appendix C of text): (a) Appendix c lists the standard entropy of both 1iquid and gaseous (b) Use this and other standard entropies to calculate as for: (c) Use standard entropies to calculate AS for: (d) Use standard Gibbs energies of formation to calculate AG° for: CH. What is the entropy of the liquid form? 3C.H. (g) ?.?. ( 1 ) + 6H (g). HNO (g) + NH:(g) NH NO (s) P,010 (s) + 16 H2(g) ? 4 PH:(g) + 10 H,O(g). 4. In standard conditions, is reaction #3d spontaneous?

Explanation / Answer

3. (a) Entropy of liquid form of C6H6 = 173.3 J/mol.K

(b) ?So = 173.3 + 6 x 130.7 – 3 x 200.9 = 354.8 J/mol.K

(d) ?Go = 4 x 25.5 + (10 x -228.6) – (-2675.2) + 16 x 0 = 491.5 kJ/mol

4. The reaction #3d is not spontaneous as the Gibbs energy is positive.

Name

Standard entropies S° / (J/mol.K)

C6H6 (liquid)

173.3

C2H6 (gas)

200.9

H2 (gas)

130.7

HNO3(g)

266.3

NH3(g)

192.3

NH4NO3 (s)

151.1

Standard Gibbs energies G° / (kJ/mol)

P4O10(s)

-2675.2

H2(g)

PH3(g)

25.5

H2O(g)

-228.6