Again we have to use this formula:
p*V = n*R*T
p in Pa... 750 torr = 99991.78 Pa
V in cubic metres = 0.002 m3
R is a constant = 8.3145 whatever
T is in Kelvin = 300.15 K
n = (99991.78*0.002)/(8.3145*300.15) = 0.08 mol
So we have 0.08 mol gas in the bottle, and we know the molar mass.
1 mol of the gas is 29 g.
So 0.08 mol of the gas is 29*0.08 mol = 2.32 g of air. Pretty light huh?
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