The dissolution of ammonium nitrate in water is given by the equation below. Which statement best describes what an energy graph of this reaction would look like?

Question

The dissolution of ammonium nitrate in water is given by the equation below. Which statement best describes what an energy graph of this reaction would look like?

NH4NO3(s) + heat --> NH4 + (aq) + NO3 - (aq)

The reactants and products would appear at a low energy state.
The reactants and products would appear at a high energy state.
The reactants would appear at a lower energy state than the products.
The reactants would appear at a higher energy state than the products.

Answer 1

The correct statement is, "The reactants would appear at a higher energy state than the products." This is because energy must be added to the system, in the form of heat, in order for the solid ammonium nitrate to dissolve into its constituent ions in solution. The reactants (solid NH4NO3) therefore have a higher energy state than the products (aqueous NH4+ and NO3- ions).