Answer:
dG will be the same -20 kcal/mol
Explanation:
The dG can be expressed in terms of the G(products) - G(reactants). If the amount of enzyme is doubled the Gibbs energy of the reactants and products will be the same, so the substraction dG has the same value
2K + Br2 ===> 2KBr
It's very ionic. The transfer of 2 electrons from K to Br2 is nearly as complete as it can be.