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Unformatted text preview: Oct 13‐15, as usual.
2 Exp 4 – Molar mass using the Dumas method
MOLAR MASS: Defined as the mass of one mole of a substance. But how do you weigh a gas? You can't put a gas in a weighing pan like you did the pennies. So instead, we use a Dumas tube, which is a tube with a very narrow neck. – At room temperature, the tube is filled with air at atmospheric pressure.
– The mass is that of the tube + air (blue dots) • When a volatile liquid (red) is placed in the tube, at first the liquid is in equilibrium with its vapor (red dots) and it also contains air.
• As the tube is heated, the liquid vaporizes and the air is swept out of the tube. At temperatures above th...
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- Fall '06