The decomposition of hydrogen peroxide to form oxygen and water follows the reac

Question

The decomposition of hydrogen peroxide to form oxygen and water follows the reaction

2H2O2(aq) <--> O2(g) + 2H2O (l)

Thermodynamic data for the chemicals:
H2O2(aq): delta H = -187.8 kj/mol delta S = 109.6
O2 (g): delta H= 0 delta S= 205.2
H2O (l): delta H = -285.8 delta S= 70.0

A) Calculate Gibbs Free Energy under standard conditions.

B) Calculate Gibbs Free Energy change for this reaction if the concentration of hydrogen peroxide is reduced to 0.050M and the pressure of oxygen is reduced to 150 torr (the standard pressure of oxygen in the atmosphere).

C) Oxygen is an element in its standard state, why is delta S not 0 for oxygen like delta H?

Explanation / Answer

A) Delta G=delta G products-detla G reactants

delta G products=deltaH products-T(deltaS products)

=(2(-285.8)+0)-298(2(70)+205.2)= -517.6-298(390.2)=-1,16,797.2kj/mol

delta G reactants=deltaH reactants-T(deltaS reactants)

=2(-187.8)-298(2(109.6))=-375.6-298(219.2)=-65,697.2kj/mol

Delta G=delta G products-detla G reactants=-116797.2-(-65697.2)kj/mol=-51,100kj/mol

C) The heat of formation is zero for homonuclear diatomic molecules, like O2,N2 and H2. according to third law of thermodynamics the entropy of the universe is increasing for every change that occurs.

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