Click to see entire Chemistry category
Equipment: beaker, conical flask, aluminium foil, elastic band, mass scales, propanone, pin, clamp, water, thermometer, graduated cylinder, barometer
1. Two thirds fill a beaker and heat to almost boiling, keeping temperature constant.
2. Cover the mouth of a conical flask with aluminium foil and an elastic band. Find total mass of flask, foil and band.
3. Add 3 to 4 cm³ propanone to flask. Recover with foil, and use a pin to prick a small hole in the centre.
4. Attach clamp to flask and immerse in water, moving flask up and down.
5. When flask appears empty, remove flask immediately. Record exact temperature of water.
6. Allow flask to cool and thoroughly dry outside of flask. Find mass of flask, foil, band and contents and by subtraction, calculate mass of vaporised liquid.
7. Find volume of flask by filling it with water and transferring water to graduated cylinders.
8. Find room pressure using a barometer.
9. Calculate Relative Molecular Mass
Results
Mass of condensed vapour of volatile liquid: 0.67g
Atmospheric pressure: 100 812 Pa
Temperature of water: 368 K
Volume of flask: 0.00028 m³
n = PV/RT = 0.0092 moles
Mr = m/n = 0.67/0.0092 = 72.82
