A student dissolves 10.3 g of sodium chloride (NaCl) in 250. g of water in a well-insulated open cup. He then observes the temperature of the water fall from 23.0 °C to 22.2 °C over the course of 3 minutes. NaCl(s) → Na+ (aq) + Ci (aq)

You can make any reasonable assumptions about the physical properties of the solution. Be sure answers you calculate using measured data are rounded to the correct number of significant digits.

a. Is this reaction exothermic, endothermic, or neither?
b. If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case.
c. Calculate the reaction enthalpy ΔHrxn per mole of NaCl.