Benzene Lab
Melting point: 5.5°C
Boiling point: 80°C
Heat of Fusion: 127 J/g
Heat of Vaporization: 551 J/g
Sample size: 100g
Sp. Heat (solid): 1.5 J/g°C
Sp. Heat (liquid): 1.7 J/g°C
Sp. Heat (gas): 1.0 J/g°C 1.
How much heat is required to melt the sample at the melting point?
Heat needed = mass * Hf of Benzene
Heat needed = 100 g * 127 J/g°C
Heat needed = 12700 J
2. How much heat is required to boil the sample at the boiling point?
Heat needed = mass * Hv of Benzene
Heat needed = 100g * 551 J/g°C
Heat needed = 55100 J
3. How much heat is required to raise the temperature of the sample from 20°C below melting
point to the melting point?
Heat needed = mass * specific heat * difference in final and initial temperature
Heat needed = 100g * 1.5 J/g°C * (5.5°C+14.5 °C)
Heat needed = 150 J * 20°C
Heat needed = 3000 J
4. What is the difference in temperature between melting and boiling point?
80°C – 5.5°C = 74.5°C
5. How much heat is required to raise the temperature of the sample of the liquid phase from the
ending of melting to the beginning of boiling?
Heat needed = mass * specific heat * difference in final and initial temperature
Heat needed = 100 g * 1.7 J/g°C * 74.5°C
Heat needed = 12665 J
6. How much heat is required to raise the temperature of the sample of the gas phase from the end of
boiling to 20°C above the boiling point?
Heat needed = mass * specific heat * difference in final and initial temperature
Heat needed = 100g * 1.0 J/g°C * (100°C-80°C)
Heat needed = 100 J * 20°C
Heat needed = 2000 J
7.
A. How many minutes are needed to reach the melting point?
12700/ 400 = 31.75
Approximately 32 min.
B. How many minutes are needed to heat liquid phase to the boiling point?
55100/ 400 = 137.75
Approximately 138 min.
C. How many minutes are needed to change phase at the melting point?
3000/ 400 = 7.5
Approximately 8 min.
D. How many minutes are needed to change phase at the boiling point?
12665/ 400 = 31.66
Approximately 32 minutes.
E. How many minutes are needed to reach the maximum temperature from the boiling point?
2000/ 400 = 5
5 minutes.
8. What is the total time, in minutes, from beginning of melting to the end of boiling?
31.75 + 137.75 + 7.5 + 31.66 + 5 = 213.66
9. What phase is the substance at 50°C?
Liquid phase
Approximately 214 minutes.