# Molar mass of helium

History Scientific discoveries The first evidence of helium was observed on August 18,as a bright yellow line with a wavelength of The line was detected by French astronomer Jules Janssen during a total solar eclipse in GunturIndia. On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D3 because it was near the known D1 and D2 Fraunhofer line lines of sodium. Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas liberated by sulfuric acidhe noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. By the way, solid and liquid volumes are responsive to temperature and pressure, but the response is so little that it can usually be ignored in introductory classes.

So, for gases, we speak of "standard gas density. If you discuss gas density at any other set of conditions, you drop the word standard and specify the pressure and temperature. Also, when you say "standard gas density," you do not need to add "at STP.

It does no harm to say "standard gas density at STP," it's just a bit redundant. You can calculate the standard gas density fairly easily.

Just take the mass of one mole of the gas and divide by the molar volume. For example, using nitrogen, we would have: For water, we have: The behavior of "real" gases diverges from predictions based on ideal conditions. Small gases like H2 at high temperatures approach ideal behavior almost exactly while larger gas molecules NH3 at low temperatures diverge the greatest amount.

These "real" gas differences are small enough to ignore right now, but in later classes they will become important. Here is a brief video explaining the conversion.

The density of a gas is measured at 1. What is its molar mass? Notice I left the units off everything. This solution exploits a rearrangement of the ideal gas law. What is the molar mass of a gas which has a density of 0. Convert mmHg to atm Please note that I used Some teachers require the use of The ChemTeam always felt that was good enough, but some teachers disagree.

Yours may be one of those people Are teachers people? Anhydrous aluminum chloride sublimes at high temperatures. What density will the vapor have at degrees Celsius and 0. However, I would have then divided the grams by that volume in this last step and wound up with 3. What is the density of air at For both solutions, we need the "molecular weight" of air:(1 u is equal to 1/12 the mass of one atom of carbon) Molar mass (molar weight) is the mass of one mole of a substance and is expressed in g/mol.

Weights of atoms and isotopes are from NIST article. Helium-4 makes up about one quarter of the ordinary matter in the universe by mass, with almost all of the rest being hydrogen. When liquid helium-4 is cooled to below kelvin (– °C) it becomes a superfluid, with properties that are very unlike those of an ordinary liquid.

The molecular weight of a substance, also called the molar mass, M, is the mass of 1 mole of that substance, given in M gram. In the SI system the unit of M is [kg/kmol] and in the English system the unit is [lb/lbmol], while in the cgs system the unit of M is [g/mol].

Molecular weight is. Its volume is mL at a temperature of 85 oC and a pressure of mmHg. Find the molar mass of the gas. The mixture also contains helium gas. What is the partial pressure of the helium gas?

What mass of helium gas is present in a L sample of this mixture at K. CO. 2, mmHg. The molar mass of H2, which is the chemical formula for dihydrogen, is grams per mole with a standard deviation of plus or minus grams per mole. Oct 05,  · To convert grams to moles, start by multiplying the number of atoms by the atomic weight for each element in the compound.