PURPOSE: To demonstrate that one mole of gas occupies 22.4 liters at STP.
DESCRIPTION: Pour liquid nitrogen into the small beaker and let it boil down to about 35 ml. The density of liquid nitrogen is 0.808 g/ml, so one mole has a mass of 28 grams and occupies about 35 ml. Install the neck of the balloon over the beaker, seal the side nipple and allow the liquid nitrogen to evaporate, filling the balloon. Determine the average circumference of the balloon and from that calculate the diameter. The volume of one mole of nitrogen gas is then V=4/3 pi r^3, which can be readily calculated. This determination is good to better than ten percent.
REFERENCES: (PIRA unavailable.)
EQUIPMENT: Liquid nitrogen, small flask with nipple, styrofoam insulating pad, measuring tape, balloon, styrofoam cup to pour LN.
SETUP TIME: 5 min.
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