TBR thermo

[greenseeking]

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Hi please see attached passage and question.
Which of the following statements is a valid conclusion from the observations of Beaker 3?

Answer is B. Solvation of NH4CL is endothermic.

If you see in the graph, the temperature is INCREASING. So wouldn't it be exothermic?

Thanks.

 

[indianjatt]

To me it seems like the reaction mixture did not reach the initial temperature of the water. Thus, some energy must have been lost from the h2o and gone into the ammonium mixture. Since energy goes into the system, it is an endothermic reaction.

 

[Ansar]

EDIT: Nevermind. Read question incorrectly.
EDIT2: It still seems like it should be B, though, just out of observation that the temperature dropped (or is that the whole not yet calibrated blurb they mention?) Or the fact that the temperature is lower than the starting temperature.

 

[greenseeking]

okay. I see what you guys are saying-- that we should only see that extrapolated point and that it decreased... thanks.

 

[Singhp03]

also if you consider the introductory temp as room temp (20-25 degree) an endothermic reaction would explain the initial drop, and thermal equilibrium of the solution with the room would explain the later rise.