Lab 4: Calorimetry At Home Laboratory
The first experiment looks at the heat of fusion of ice: the amount of heat needed to convert a solid into a liquid at constant temperature and pressure is the heat of fusion of the substance. The molar heat of fusion is the amount of heat energy required to completely change one mole of solid into one mole of liquid at its melting point. In this experiment, the molar heat of fusion of ice was determined experimentally and compared mathematically to its standard value.
Roughly 300mL was heated to about 70oC and 150mL of the warm water was poured into a coffee cup calorimeter. A lid was placed on the calorimeter and a thermometer placed through a hole in the lid into the liquid. Once the thermometer had equilibrated, the temperature of the liquid was noted. One or two pieces of ice were then placed in the liquid, the lid replaced on the calorimeter, and the liquid and ice stirred with the thermometer. The temperature of the water/ice mixture was monitored and the lowest temperature observed was noted. The lid was then removed from the calorimeter and the new volume of liquid measured and recorded. The experiment was repeated for two more trials.
1. Moles of ice melted: Density of water = 1g/mL
Volume of ice melted = 18 mL
Molar weight of water = 18g/M
Therefore moles of ice melted = 1M
Where Q = total heat absorbed = 20
m = mass of substance = 18 = 20/18
= 1.11 c/g/oC (O'Brien, 1996)
1 calorie = 4.18 Joules so 1.11c = 1.11 x 4.18J
= 4.64kJ/mol
1. The average heat of fusion of ice from the three trials was 4.667kJ/mol. The actual heat of fusion of ice is 6.01kJ/mol. The percent error in the determination of the value for the molar heat of fusion of ice was:...