Consider the gas-phase reaction of hydrogen and iodine at 298.15K and the graph

Question

Consider the gas-phase reaction of hydrogen and iodine at 298.15K and the graph showing the free energy of the Hz-12-Hl mixture Answer the questions below H,(g)+12e) 2Hre) AGo-54.226k lmolHz 1mol2 G" =-70.234 ki 2mol HI (a) Does the equilibrium favor the reactant or the products? O neither O products O way to tell There is no reactants (b) Where is the equilibrium position on the graph? O Halfway between the reactants and products O At the highest point in the curve on the right (product side) O At the highest point in the curve on the left (reactant side) O At the lowest point in the curve Number (c) What is the value of the equilibrium constant at 298.15 K? Assume a 1.000-L container

Explanation / Answer

Answer –

We given reaction

H2(g)+ I2(g)<------> 2 HI(g)

a) Product.

At the equilibrium product is favour, because in the gas phase reaction there is energy of reactant is high than product and we know reaction is always favoured at lowest energy. So this is the exothermic reaction and reaction favoured at product side.

b) At the lowest point in the curve

For this gas phase reaction there reaction equilibrium favoured at product side and it is the position of equilibrium at lowest energy means the equilibrium at the position where curve is at lowest point.

c) Now we need to first calculate standard free energy for the given reaction –

   H2(g)+ I2(g)<------> 2 HI(g)

We know formula ,

Gorxn = sum of Go product – sum of Go reactant

   = [2*Go HI(g)] – [Go H2(g) + GoI2(g)]

   = (2*1.3 kJ/mol0 – ( 0.00 kJ/mole + 19.2 kJ/mole)

   = -16.6 kJ/mol

Now can calculate the equilibrium constant

We know formula,

Gorxn = - RTlnK

We need Gorxn in J/mol, because the value of R in the J.

We know, 1 kJ = 1000 J

So, -16.6 kJ = ?

= -1.66*104 J

Now plugging the value in the formula,

-1.66*104 J/mol = - 8.314J.mol-1.K-1 * 298.15 K * ln K

-1.66*104 J/mol = - 2478.81* ln K

So, ln K = -1.66*104 J/mol / - 2478.81

              = 6.696

Now taking antiln from both side,

K = 809.7

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