1. A sample bulb contained 0.712 g H2 (g) at a certain temperature and pressure. Under the same conditions of temperature and pressure, the bulb can hold 13.0 g of an unknown gas. What is the molar mass of the unknown gas?
Obtaining H2 volume from the ideal gas law (assuming STP) and then using that volume to obtain the unknown gas density (with STP) is the correct way to obtain the molar mass?
I would appreciate some help
Thank you.
2007-06-24 06:11:15 · 5 answers · asked by chem 1 in Science & Mathematics ➔ Chemistry
You do not actually need to use the ideal gas law. Why? Because at a give T, P, V all (More or less) ideal gases have the same number of particels/moles in a give volume, no matter how large the particles or what elements they are (that is one of the definitions of an ideal gas).
Thus calculate the number of moles in 0.712 g of H2: 0.712g* 2 g/mol (molar mass of H2) to get moles of H2. This equals the moles of you unknown gas. Then calculate back to the molar mass: grams of gas/moles of gas = molar mass in g/mol.
Real gases are somewaht different from ideal gases, but the difference is negligable.
2007-06-24 06:25:58 · answer #1 · answered by Manuela S 3 · 0⤊ 0⤋
All gases are assumed to obey the ideal gas law, PV = nRT.
Since the temperature, pressure and volume are the same for both gases, the only difference is the molecular mass.
The molecular mass of H2 is 2 grams. Just set up a ratio between the grams of the unknown gas and the grams of Hydrogen, and multiply by the 2 grams molecular mass of Hydrogen, and you are done.
2007-06-24 06:18:58 · answer #2 · answered by reb1240 7 · 0⤊ 0⤋
You can do this in an easier way. If the other gas gives the same pressure at the same temperature, its number of moles as shown by the formula pV=nRT is the same. The weight of a gas is equal to the number of moles twice molecular mass
so mH2 = n* MH2 (1)
and mX= n*MX (2)
dividing (2) by (1)
MX= MH2*mX/mH2 MH2 =2
and MX= 2*13/0.712 =36.5 G
2007-06-24 06:47:35 · answer #3 · answered by maussy 7 · 0⤊ 0⤋
pV = nRT
pV/RT = K a constant because p, V and T are constant in this case
Therefore in this case
K = n = g/M where M = m.w.; now it is just a proportionality problem
0.712 g/2 g/mole = 13 g/M or
M = 13 * 2 / 0.712
2007-06-24 06:18:03 · answer #4 · answered by GTB 7 · 0⤊ 0⤋
I think king of dudes is on the right track. If it effuses 3.08 times faster than F then it goes at 117.04g/mol. The identity is...UUS? Idk..i'm wrong lol
2016-05-19 04:41:18 · answer #5 · answered by geralyn 3 · 0⤊ 0⤋