Standard entropy of X2, Y2 and XY3 are 60, 40 and 50

• Chemical Thermodynamics

Standard entropy of X₂, Y₂ and XY₃ are 60, 40 and 50 J K^–1 mol^–1, respectively. For the reaction, 1/2 X₂ + 3/2 Y₂ → XY₃, ΔH = –30 kJ, to be at equilibrium, the temperature will be

1. 500 K
2. 750 K
3. 1000 K
4. 1250 K

Answer

1/2X₂ + 3/2Y₂ → XY₃

ΔS°_reaction  = ΔS°_products - ΔS°_reactants

= 50 – 60/2 - 3*40/2

= -40 J/mol

ΔG = ΔH – TΔS

ΔH = -30 kJ, ΔS = -40J/(K mol)

At equilibrium, ΔG = 0

T = ΔH/ΔS = 750 K

The correct option is B.