Question

Consider the strengths of the following changes:

separate NaI into its ions: 702 kJ/mol

separate water into molecules 60 kJ/mol

form solvent shells around sodium ions and iodide ions 770 kJ/mol

When dissolving NaI in water, the change is likely to be (endo/exo thermic) and the reaction will feel (hot/cold) to the touch

Question 2 options:

endothermic, hot


endothermic; cold


exothermic, hot


exothermic, cold

Answer 1

lets gooooooooooo

Answer 2

separate NaI into its ions: 702 kJ/mol
separate water into molecules 60 kJ/mol
form solvent shells around sodium ions and iodide ions 770 kJ/mol

So it takes 702 kJ/mol energy for this step + 60 kJ/mol for step 2. Then you get back 770 kJ/mol for step 3.
dH = 702 + 60 - 770 = -8 kJ/mol
That tells you that NaI dissolves in water, it is exothermic, so the vessel will feel warm.