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vapour density = mass of n molecules of gas / mass of n molecules of hydrogen
(By definition, the molar mass of a gas is the ratio of the mass of one molecule of gas to that of an hydrogen atom under similar conditions.)
vapour density = molar mass of gas / molar mass of H2
vapour density = molar mass of gas / 2
vapour density = Â½ × molar mass
(and thus: molar mass = 2 × vapour density)
In many web sources, particularly in relation to safety considerations at commercial and industrial facilities in the U.S., vapour density is defined with respect to air, not hydrogen. Air is given a vapour density of one. For this use, air has a molecular weight of 29 atomic mass units, and all other gas and vapour molecular weights are divided by this number to derive their vapour density. For example, acetone has a vapour density of 2 in relation to air. That means acetone vapour is twice as heavy as air. This can be seen by dividing the molecular weight of Acetone, 58.1 by that of air, 29, which equals 2.
With this definition, the vapour density would indicate whether a gas is denser (greater than one) or less dense (less than one) than air. The density has implications for container storage and personnel safetyâ€”if a container can release a dense gas, its vapour could sink and, if flammable, collect until it is at a concentration sufficient for ignition. Even if not flammable, it could collect in the lower floor or level of a confined space and displace air, possibly presenting a smothering hazard to individuals entering the lower part of that space.
It is recommended that individuals confirm the definition of vapour density being used in their specific context.
From Yahoo Answers
Answers:according to wikipedia Density of acetone is 0.7925 g/cm3
Answers:find mass 410 ml @ 0.788 g/ml = 323.08 grams find moles, using molar mass 323.08 grams @ 58.08 g/mol = 5.563 moles using avagadro's number 5.563 moles @ 6.022 e23 molecules / mol = 3.35 e24 molesules your answer is 3.34 X10^24 molecules
Answers:I don't know what the density of acetone is. Its probably around .65. You can look in the handbook of chemistry and physics.
Answers:density=mass/Volume and mass=M x n so n=density x Volume/M You need is M (Molar mass??? sorry I'm french, we call it masse molaire so I'm just guessing what it is in English) So either it's answer one, you're missing an information unless you're allowed to calculate M thanks to the formula and the individual M of the different atoms. M = 3M(C) + 6M(H) + M(O) = 3x12 + 6 + 16 = 58 g/mol n = (851 x 7.85) / 58 = 115 mol NB : 0.851 g/ml = 851 g/L I've just rechecked my calculations and found out where I'd been wrong (I'd multiplied M(O) by 8 for some reason... idiotic). So there it is, answer 3. I hope it's not too late...