[MurderousTreeNut]

On my last test there was a question saying “NH4Cl is dissolved into water. The temperature change measured decreases over time. Is it exothermic, endothermic or is there not enough information?” I said there was not enough information because there is no information on an increasing or decreasing temperature just a decreasing rate of change. The answer key said it was endothermic. Am I correct, and if so how do I explain it to my professor?

[Babcock_Hall]

The question could have been worded more clearly.  It seems to me that it could mean either that the temperature fell or that the rate of change in temperature fell.  I am not sure whether or not it is worth arguing.

[Corribus]

Wording of the problem is ambiguous. Your argument has merit. Out of principle you should make your case to the instructor, but don't be surprised if it falls on deaf ears.

[Babcock_Hall]

@OP, Taking as a given that this process is endothermic, what other conclusions can be drawn about the thermodynamics of this dissolution process?