When a sample of NH4SCN(s) is mixed with Ba(OH)2⋅8H2O(s) in a glass beaker, the mixture changes to a liquid and the temperature drops sufficiently to freeze the beaker to the table. Which statement is true about the reaction?
a. The process is endothermic and ΔH is negative.
b. The process is endothermic and ΔH is positive.
c. The process is exothermic and ΔH is negative.
d. The process is exothermic and ΔH is positive.