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Q.	Vapor density?	Related Search: Chemistry
	A compound X contains element Q. Percent by weight of element Q is 64.8%. The Vapor Density of compound X at 27 C and 750 mm Hg is 3.53 g per liter. Calculate molecular weight of compound X.
A.	There isn't enough information, you aren't given a second volume.

Q.	What are possible errors for molecular mass determination by vapor density method?	Related Search: Chemistry
	List the most serious sources of error that could be anticipated, where possible and estimate probable effect on the final result by using the vapor density method.
A.	Well I am unfamiliar with the vapor density method or the experiment you must do to figure it out, but many sources of error are pouring water from one container to another will decrease volume, bubbles in water will increase volume, reading a thermometer incorrectly, spilling water, not heating or cooling a substance for long enough, mathematical errors..... Just think of really obvious but tiny details. I hope I kind of helped!

Q.	How to find molecular formula from vapor density, pressure and temp?	Related Search: Chemistry
	A certain compound containing only carbon and hydrogen was found to have a vapor density of 2.550 g/L at 100°C and 760 mm Hg. If the empirical formula of this compound is CH, what is the molecular formula of this compound? thank you very much sfyankee for your help.
A.	use the formula: MM = dRT/P 100°C = 373K 760 torr = 1atm MM = (2.550g/L)(0.08206/mol*K)(373K)/(1atm) MM = 78.05g/mol MM CH = 13 g/mol 78.05g/mol / 13g/mol = 6 C6H6

Q.	What is the density of the ethanol vapor?	Related Search: Physics
	Actual question: An industrial process can be used to change ethylene (CH2CH2) into ethanol (C2H5OH). The process uses a catalyst, high pressure (6.8MPa), and temperature of 3x10^3 degrees Kelvin. What is the density of the ethanol vapor under these conditions?
A.	One could use the gas laws to come up with a superficial answer to this, but it could well be wrong: under that much pressure, ethanol may well not act as an ideal gas.

Q.	What is the density of carbon tetrachloride vapor at STP?	Related Search: Chemistry
	How do I find the density of carbon tetrachloride vapor at STP?
A.	STP means standard temperature and pressure T = 273 K P = 1 atm We need to find the density = (mass / volume) We can find the volume of the gas if we use the ideal gas law (pressure) x (volume) = (# of moles) x (temperature) x R V = (n x T x R) / (P) Because density is an intensive property (it does not change with the amount), we will assume one mole of CCl4 So now P = 1 atm T = 273 K n = 1 mole R = 0.0821 (Latm) / (Mole K) V = (1 mole x 273 K x 0.0821((Latm)/(moleK))) / (1 atm) = 22.4 L This volume is expected with STP of any ideal gas Now we need mass. We assumed 1 mole of CCl4 to find the volume, so we find the mass of 1 mole of CCl4 1 mole CCl4 x (154 g/mol) = 154 g CCl4 Now we solve for density D = m/V = 154 g/22.4 L = 6.875 g/L 0.006875 g/ mL [Link]

Click on the word below to see the definition:

Vapour density is the density of a vapour in relation to that of hydrogen. It may be defined as mass of a certain volume of a substance divided by mass of same volume of hydrogen.

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.)

Therefore:

vapour density = molar mass of gas / molar mass of H₂

vapour density = molar mass of gas / 2

vapour density = ½ × molar mass

(and thus: molar mass = 2 × vapour density)

[edit] Alternative definition

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 an arbitrary vapour density of one. 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 safety--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.

[edit] See also

relative density (also known as specific gravity)

[edit] External links

MSDS Glossary of Terms - Vapor Density

Retrieved from "http://en.wikipedia.org/wiki/Vapour_density"

Categories: Density

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