Solution

The reaction is an endothermic reaction. Heat is absorbed as the temperature decreases.

The calibration factor of the calorimeter is given by the expression below.

Obtain the amount of energy absorbed from 0.996 grams of ammonium nitrate

Calibration factor X change in temperature = 468 X 0.672 = 0.314KJ

The enthalpy change is energy/mol

SO!

Step 1) Mole of ammonium nitrate added = 0.996 /80 = 0.0125 mole

Step 2) Divide the amount of energy by the number of mole of ammonium nitrate.

0.314/ 0.01245 = 25.2Kj/mol

Note how the enthalpy change has a positive sign. This indicates an endothermic reaction (heat absorbed from the surroundings).

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