CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
A student dissolves 3.0g of NH4NO3 in 50.0g of water. The temperature of the mixture decreases from 22.4∘C to 17.9∘C. Which statement best describes the energy changes that occur during this process?
(a) The dissolution is exothermic because breaking the ionic bonds in NH4NO3 releases heat, which the water absorbs, cooling the solution.
(b) The dissolution is endothermic because thermal energy is absorbed from the water, causing the temperature to drop.
(c) The dissolution is exothermic because the negative value of ΔT in q=mcΔT indicates a negative ΔH.
(d) The dissolution is exothermic because the ion–dipole attractions formed between the ions and water release more energy than is needed to separate the ions.