Lab Report

Siddharth Rajendran
Chemistry HL
Urea Dissolution Lab
Raw Data:-

(Expected Values)

Change in Enthalpy: 14 kJ mol-1

Change in Gibbs free energy: 6.86 kJ mol-1

Change in Entropy: 69.5 J mol-1

Molar Mass of Urea: 60.06 g mol-1

Heat Capacity: 4.184 J g-1º

Data Table 1: To calculate the Enthalpy change

Mass of Urea Tablet (g) (±0.01g) | Volume of Water(mL) (±0.05mL) | Initial Temperature (Cº) (±0.2 Cº) | Final Temperature(Cº) (±0.2 Cº) | 3.04 | 50.0 | 21.3 | 17.4 |

Initial Observations:-

* There was a decrease in temperature at a fast rate. * The temperature of the solution was slowing down continuously but the rate started decreasing. * The Urea dissolved and the rate was decreasing continuously. * The temperature gradually started to increase after almost the Urea present had dissolved.

Data Table 2:

Mass, Volume and Temperature during Dissolution of Urea (To calculate Keq)

Mass of Urea(g) (±0.01g) | Initial Temperature(Cº) (±0.2 Cº) | Final TemperatureCº) (±0.2 Cº) | Initial Volume(mL)(±0.05 mL) | Final Volume(mL)(±0.05 mL) | 3.76 | 21.4 | 22.9 | 5.02 | 7.14 |

Processing Raw Data

* Determining the Final temperature of dissolution of Urea in the Styrofoam cup.

Graph 1: The Change in temperature due to the Dissolution of Urea

In order to calculate the final temperature of the dissolved mixture, the linear fit of the graph was utilized. The final time measure was 600 seconds. Substituting the value of time in to the linear equation:-

Temp= 0.008997 ºC/s (600) + 17.25 ºC

Final Temperature= 17.8 ºC ±0.2 ºC

* Calculation of enthalpy change

Using the formula
Q = m * C * (∆T) m= mL of Water C= Heat Capacity ∆T= Change in Temperature

m = 50.0 mL ± 0.01 mL c = 4.184 J g-1 ºC-1
∆ T= 17.4 Cº (±0.2 C) - 21. 8 Cº