Answer:
19.91 J/K
Explanation:
The entropy is a measure of the randomness of the system, and it intends to increase in nature, thus for a spontaneous reaction ΔS > 0.
The entropy variation can be found by:
ΔS = ∑n*S° products - ∑n*S° reactants
Where n is the coefficient of the substance. The value of S° (standard molar entropy) can be found at a thermodynamic table.
S°, Cl(g) = 165.20 J/mol.K
S°, O3(g) = 238.93 J/mol.K
S°, O2(g) = 205.138 J/mol.K
So:
ΔS = (1*205.138 + 1*218.9) - (1*165.20 + 1*238.93)
ΔS = 19.91 J/K