Compare the molar masses of ammonia and air. How many times is ammonia lighter than air? How should the ammonia collection tube be positioned?
M (NH3) = 17g / mol
M (air) = 29g / mol
Since the molecular weight of ammonia is less than the molecular weight of air, ammonia is lighter than air by 29/17 = 1.7 times.
Because Since ammonia is lighter than air, the tube should be kept upside down to collect it.
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