Calculate the change in entropy if Br2 (l) is converted into gaseous Br atoms.

S° for Br2 (l) = 152.2 J / (mol•K)

S° for Br2 (g) = 245.5 J / (mol•K)

S° for Br (g) = 175.0 J / (mol•K)

197.8 J/mol

Explanation:

The conversion will happen in steps. First, the Br₂ (l) will be converted to Br₂ (g), and then to Br atoms. Thus, the change in entropy will be the sum of the change in entropy of the two steps.

Step 1

Br₂ (l) → Br₂ (g)

ΔS = ∑n*S°products - ∑n*S°reactants, where n is the stoichiometric coefficient

ΔS = 245.5 - 152.2 = 93.3 J/K

Step 2

Br₂ (g) → 2Br (g)

ΔS = (2*175.0) - 245.5 = 104.5 J/mol

Thus, the total change in entropy is

ΔS = 93.3 + 104.5

ΔS = 197.8 J/mol

197.8 J / (mol•K).

Explanation:

∆S° = [Σ bS° products] - [Σ aS° reactants], where b and a are the coefficients of the products and the reactants in the balanced reaction equation.

Br₂ (l) ⟶ 2 Br (g)

∴ ∆S° = [2 x S° Br (g) ] - [S° Br₂ (l) ]

∴ ∆S° = [ (2) (175.0 J / (mol•K) ] - [152.2 J / (mol•K) ] = 197.8 J / (mol•K).