When 1.0 mole of MgSO4 is dissolved in water contained in a calorimeter, the temperature of the water and dissolved ions increases. Therefore the sign of ΔH for this reaction is , heat is transferred the system the surroundings, and the reaction is classified as .

negative , from , to , exothermic

Explanation:

An endothermic reaction is a type of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.

An Exothermic reaction is a type of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.

Endothermic reactions are those in which heat is absorbed by the system from the surroundings and exothermic reactions are those in which heat is released by the system to the surroundings.  for Endothermic reaction is positive and  

As on dissolution of salt, the temperature of water increases, the heat has been released from system into surroundings and thus is negative.