molar mass of unknown gas?
A sample of an unknown gas weighs 0.419 grams and produced 5.00L of gas at 1.00atm (unknown gas only) and 298.15K, what is the molar mass (g/mole) of this unknown gas? Remember to adjust your calculated answer for significant figures.
- Dr WLv 71 month ago
let's assume the gas is ideal and let's use dimensional analysis to setup and solve this problem
- pisgahchemistLv 71 month ago
Molar mass of a gas ....
PV = nRT ............ ideal gas equation
PV = mRT / M ..... n = m / M ...... m = mass, M = molar mass
M = mRT / PV ..... solve for M
M = 0.419g x 0.08206 Latm/molK x 298.15K / 1.00 atm / 5.00L
M = 2.05 g/mol .... to three significant digits
That's close to the molar mass of hydrogen (H2), which, to three significant digits, has a molar mass of 2.02 g/mol
- lenpol7Lv 71 month ago
Use the Ideal Gas Eq'n
PV = nRT
n = PV/RT
P = 1 atm = 101532 Pa
V = 5.0L = 0.005 m^3
R = 8.314 The Gas Constant
T = 298.15 K
n = (101532 X 0.005) / ( 8.314 X 298.15)
n = 0.2047 moles.
Mr = 0.419 g / 0.2017 moles
Mr = 2.38 g/mole