I have got some confusion .
In the Ncert Chemistry Tb , part 1 , pg 161 . left hand side , bottom of the page , it is given in bold that delta H is negative for exothermic reactions which evolve heat during the reaction and delta H is positive for endothermic reactions which absorb heat from the surrondings .
In Enthalpy change video lesson of topperlearning , part 1 , just after 4.21 mins , it is given that
For , NH4NO3 (s) --> NH4NO3 (aq) , since the temperature decreases during the reaction , it is positive enthalpy of solution . ( but how is it positive ? i guess both delta H and enthalpy change of a solution is almost change . Since the temp decreases here , it is endothermic , so it should be positive right ? )
Plz explain this clearly .. Are both of the above processes different from each other and are the sign conventions vice versa for each other ?