Question

2. For each pair of substances listed here, choose the one having the larger standard entropy value at 25ºC. The same molar amount is used in the comparison. Explain the basis for your choice. (12 points) a. Li(s) or Li(l) b. C2H5OH(l) or CH3OCH3(l) c. Ar(g) or Xe(g) d. CO(g) or CO2(g) e. O2(g) or O3(g) f. NO2(g) or N2O4(g)

Answer 1

Answer:

a)Li (liquid)

b) CH₃OCH₃ (liquid)

c) Xe (gas)

d) CO₂ (gas)

e) O₃ (gas)

f)N₂O₄ (gas)

Explanation:

Entropy is the measure of the degree of randomness in a thermodynamic system.

The entropy of gases is more than liquids and the entropy of liquids are more than solids. This is because gases are weakly held and posses higher degree of randomness and solids are mostly ordered.

a)Li (liquid)

Liquids are less ordered than solids, therefore greater entropy  

b) CH₃OCH₃ (liquid)

It has weaker intermolecular forces, so molecules are in less fixed position when compared to C₂H₅OH (liquid) which posses hydrogen bonding. So, CH₃OCH₃ has greater entropy

c) Xe (gas)

It has greater value of molar mass than Ar (g), therefore Xe (g) has greater entropy .

d) CO₂ (gas)

It has greater molar mass than CO (gas); therefore CO₂ (gas) has greater entropy.  

e) O₃ (gas)

It not only does O₃ have a greater molar mass than O₂ (gas) but also, it is more complex that O₂ which means that it can exhibit more vibrational motion; therefore O₃ (g) has greater entropy.  

f)N₂O₄ (gas)

It has greater molar mass than NO₂(g) ; therefore N₂O₄(g) has greater entropy.