Vapour pressure of water below 100°C – molar heat of vaporisation
Principle
The vapour pressure of water in the range of 40 °C to 85 °C is investigated. It is shown that the Clausius-Clapeyron equation describes the relation between temperature and pressure in an adequate manner. An average value for the heat of vaporisation of water is determined.
Benefits
- Compact, easily transportable setup
- For both demonstration and student experiments
- No gas burner required – Easy to operate and no consumption of consumables
- No open flame in the setup – Reduction of thermal hazard
Water, distilled 5 l
Round flask, 100 ml, 3-n., 3 x GL25
Hotplate magnetic stirrer with connection for electronic contact thermometer, 3 ltr., 230 V
Glass tubes,straight, 200 mm, 10
Stopcock,1-way,r.-angled, glass
Universal clamp with joint
Students thermometer,-10…+110°C, l = 180 mm
Vacuum tube, NBR, 6/14mm, 1 m
Gasket for GL25, 8mm hole, 10 pcs
Beaker, 400 ml, low-form
Beaker, 600 ml, low-form
Magnetic stirring bar 30 mm, cylindrical
Glass tube 200 mm ext. d=8 mm
Support base DEMO
Support rod, stainless steel, 750 mm
Support rod, stainless steel, l=370 mm, d=10 mm
Rotary valve vacuum pump, two stages, 115 V / 230 V
Manometer -1.0…0.6 bar
Right angle clamp expert
Tasks
- About 250 ml of demineralised water are allowed to boil for about 10 minutes to eliminate all traces of dissolved gas. The water is then cooled down to room temperature.
- The 3-neck round flask is filled about three-quarters full with gas-free water and heated. At 35 °C the space above the water within the round flask is evacuated. Further heating causes an increase in pressure p and temperature T of water within the round flask. p and T are read in steps of 5 °C up to a maximum of T = 85 °C.
What you can learn about
- Pressure
- Temperature
- Volume
- Vaporization
- Vapour pressure
- Clausius-Clapeyron equation