Final answer:
The molar entropy of water at 298K is -226.3 J/K (per mole of H₂O₂).
Step-by-step explanation:
The molar entropy of water at 298K can be calculated using the absolute molar entropy values provided.
The formula to calculate the standard entropy change is
AS° = S° (H₂O₂) - [S° (O₂) + S° (H₂)].
Plugging in the values,
we get AS° = 1 mol H₂O₂ × 109.6 J/(mol. K) - {[1 mol H₂ × 130.7 J/(mol · K)] + [1 mol O₂ × 205.2 J/(mol.K)]}
= -226.3 J/K (per mole of H₂O₂).