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Enthalpy - Dissolution of Urea Lab Project and Two Questions

Scenario:

In lab, we added 4 (g) "solid" Urea CO(NH2)2 to a beaker and filled a buret with 50 ml H2O. We then attached a thermometer to the beaker. We added 1 ml of H2O from buret until "solid" Urea dissolved. We had to record the temperature with each 1 ml added.

We had to repeat this experiment 2 more times using different amounts of "solid" Urea each time.

The first time I used 4(g) Urea beginning temp = 21.00 degrees C.
After first 1ml H2O temp started decreasing. The lowest temp recorded was 17.03 degrees C. until Urea dissolved.

The second time I used 3(g) Urea beginning temp = 21.00 degrees C.
After first 1ml of H2O temperature started decreasing again. The lowest temp recorded was 17.03 degrees C.

The third time I used 2(g) Urea beginning temp = 21.00 degrees C.
After first 1ml of H20, temperature started decreasing then it increased. the temperature dropped to 18.99 degrees C and then rose to 19.03 degrees C.

Questions:

1. Calculate the heat of dissolution (q) of urea using the following formula: q = -s m? Where is the heat capacity (assume the heat capacity is equivalent to the heat capacity of water: 4.184 J g-l degrees C-1, m is the mass of the solution and ?T is the change in temperature.

2. Calculate the molar enthalpy change, equivalent to the heat of dissolution over n, where n is the number of moles of urea ?H=q/.

Solution Summary

The solution is a step-by-step note of observations, calculations and results. The heat of dissolution of urea and the average molar enthalpy change have been calculated.

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