Question

1. For which of the following reactions is delta S° > 0.

Choose all that apply.

i. C₂H₂(g) + 4H₂O(g)  2CO₂(g) + 5H₂(g)

ii. S(s,rhombic) + 2CO(g)  SO₂(g) + 2C(s,graphite)

iii. 4NH₃(g) + 5O₂(g)  4NO(g) + 6H₂O(g)

iv. NH₄Cl(s)  NH₃(g) + HCl(g)

v. N₂(g) + 2O₂(g)  2NO₂(g)

2. Which of the following transformations represent an increase in the entropy of the system.

Choose all that apply

i. 26 g Hg (liquid, 630K)26 g Hg (gas, 630K)

ii. 26 g Hg (liquid, 618K)26 g Hg (liquid, 246K)

iii. 1 mol Ne (0.672 atm, 497K)1 mol Ne (0.672 atm, 248K)

iv. 3 mol He (9.70 L, 198K)3 mol He (19.4 L, 198K)

v. 44 g Cr (solid, 2.130×10³K)44 g Cr (liquid, 2.130×10³K)

Answer 1

1.

An increase in entropy means number of gaseous molecules in product side is more than the gas molecules in the reactant side.

Such reactions are:

i. C₂H₂(g) + 4H₂O(g) -----> 2CO₂(g) + 5H₂(g)

1 + 4 2 + 5 : 5 < 7

iii. 4NH₃(g) + 5O₂(g) --------->   4NO(g) + 6H₂O(g)

4 + 5 4 + 6 : 9 < 10

  

iv. NH₄Cl(s) ----------> NH₃(g) + HCl(g)

0 (No gas) 1 + 1 : 0< 2

2.

solid ------> liquid --------> gas ,,, entropy increses.

As the temperature increases, entropy increases.

As volume increases, entropy increases.

i. 26 g Hg (liquid, 630K)26 g Hg (gas, 630K) (liquid to gas)

iv. 3 mol He (9.70 L, 198K)3 mol He (19.4 L, 198K) (volume increased)

v. 44 g Cr (solid, 2.130×10³K)44 g Cr (liquid, 2.130×10³K) (solid to liquid)