Exo or endo

[flossit]

Q: When solid NH4NO3 is dissolved in H2O at 25C, the solution Temperature decreases. This rxn is endothermic.
I thought it is exo as T got lower and system lost energy, please advise on this

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[Jyggaswoop]

If the solute releases energy when it dissolves, then the solution will heat up. If it takes energy to make the solute dissolve, then the solvent molecules will "steal" thermal energy from the solvent, and the temperature of the overall solution will decrease. This is why it's endothermic.

 

[DAT Destroyer]

Q: When solid NH4NO3 is dissolved in H2O at 25C, the solution Temperature decreases. This rxn is endothermic.
I thought it is exo as T got lower and system lost energy, please advise on this

If the surroundings ( solution ) gets warmer.....this indicates a reaction gave off heat....thus is exothermic. If the surroundings get colder.......the reaction has absorbed heat.......thus gets colder !!!!!

This is tricky....Don't forget it !!!!

Dr. Romano