In lab, you plan to carry out a calorimetry experiment to determine the delta H

Question

In lab, you plan to carry out a calorimetry experiment to determine the delta H for the exothermic reaction of Ca(OH)2 (s) and HCl (aq). Predict how each of the following will affect the calculated value of Delta H. (the value calculated for delta H for this reaction is a negative value so choose your answer from the following: delta H will be too low, delta H will be unaffected, delta H will be too high)

a) you spill a little bit of the Ca(OH)2 on the bench top before adding it to the calorimeter.

b) Because of a miscalculation, you add an excess of HCl to the measured amount of Ca(OH)2 in the calorimeter.

c) Ca(OH)2 readily absorbs water from the air. The Ca(OH)2 sample you weighed had been exposed to the air prior to weighing and had absorbed water.

d) After weighing out Ca(OH)2, the sample sat in an open beaker and absorbed water.

e) You delay too long in recording the final temperature.

Explanation / Answer

b) Because of a miscalculation, you add an excess of HCl to the measured amount of Ca(OH)2 in the calorimeter.

c) Ca(OH)2 readily absorbs water from the air. The Ca(OH)2 sample you weighed had been exposed to the air prior to weighing and had absorbed water.

d) After weighing out Ca(OH)2, the sample sat in an open beaker and absorbed water.

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