Problem: At 25 °C, 1.0 M methylpropene (1) was added to a reaction vessel. Upon addition of a suitable catalyst, an equilibrium mixture of three isomeric compounds formed. Methylpropene (1), cis-2-butene (2), and trans-2 butene (3) are isomers with formula C4H8, with ΔG°f = +58.07 kJ/mol, +65.86 kJ/mol and +62.97 kJ/mol, respectively. What will be the concentration of each isomer present at 25 °C once equilibrium is established? Please circle your answer(s)Hint: The sum of the equilibrium concentrations of the three species will still total 1.0 M.

FREE Expert Solution

We are asked to calculate the concentration of each isomer present at 25 °C once equilibrium is established.

Recall that the equilibrium concentrations are determined by the equilibrium constant (K): 

 

K =productsreactants



Recall that ΔG˚rxn and K are related to each other:


ΔG°rxn=-RTlnK


With this, we can derive expressions of K. 

We can use the following equation to solve for ΔG˚rxn:


ΔG°rxn=ΔG°f, prod-ΔG°f, react


We go through the following steps to solve the problem: 

Step 1: Calculate ΔG°rxn for (1) → (2) and (1) → (3)

Step 2: Derive K expressions for (1) → (2) and (1) → (3)

Step 3: Calculate the concentrations of each


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Problem Details

At 25 °C, 1.0 M methylpropene (1) was added to a reaction vessel. Upon addition of a suitable catalyst, an equilibrium mixture of three isomeric compounds formed. Methylpropene (1), cis-2-butene (2), and trans-2 butene (3) are isomers with formula C4H8, with ΔG°f = +58.07 kJ/mol, +65.86 kJ/mol and +62.97 kJ/mol, respectively. What will be the concentration of each isomer present at 25 °C once equilibrium is established? Please circle your answer(s)

Hint: The sum of the equilibrium concentrations of the three species will still total 1.0 M.


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