If 0.896 g of a gas occupies a 250 mL flask at 20 degrees Celsius and 760 mm Hg of pressure, what is the molar mass of the gas?
86.2 g/mol
86.2g/mol
PV = nRT
Solve for n = number of mols, then
n = grams/molar mass. You know n and grams, solve for molar mass.
molar mass=grams/n
64.3g/mol
86.2g/mol
To calculate the molar mass of a gas, we can use the ideal gas law equation: PV = nRT.
In this equation:
- P represents the pressure of the gas in units of pressure (mm Hg in this case).
- V represents the volume of the gas in units of volume (mL in this case).
- n represents the number of moles of the gas.
- R represents the ideal gas constant, which has a value of 0.0821 L•atm/mol•K.
- T represents the temperature of the gas in Kelvin.
First, we need to convert the given pressure from mm Hg to atm since the ideal gas constant is expressed in atm.
1 atm = 760 mm Hg
So, the pressure becomes:
P = 760 mm Hg / 760 mm Hg = 1 atm
Next, we need to convert the given volume from mL to L because the ideal gas constant is expressed in L.
1 L = 1000 mL
So, the volume becomes:
V = 250 mL / 1000 mL = 0.250 L
The temperature given in the question is already in Celsius, and we need to convert it to Kelvin.
To convert Celsius to Kelvin, we add 273.15 to the Celsius temperature.
So, the temperature becomes:
T = 20 degrees Celsius + 273.15 = 293.15 K
Now, we can use the ideal gas law equation to find the number of moles (n):
P * V = n * R * T
n = (P * V) / (R * T)
Substituting the known values:
n = (1 atm * 0.250 L) / (0.0821 L•atm/mol•K * 293.15 K)
n = 0.003229 moles
Finally, to calculate the molar mass (M), we divide the given mass (0.896 g) by the number of moles (0.003229 moles):
M = 0.896 g / 0.003229 moles
M ≈ 277.4 g/mol
Therefore, the molar mass of the gas is approximately 277.4 g/mol.