An experiment shows a 144mL sample of gas has a mass of 0.173g at a pressure of 720mmHg at a temperature of 31 degrees celsius. what is the molar mass of the sample of gas?
PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You know n and grams, solve for molar mass.
I have done this and got 31.68 for the molar mass. I converted 720.mmHg to .947 atm. T is 304 degrees K. I came up with n=5.47*10^-3. This gives me a molar mass of 31.63. I am being told this is incorrect. I am not sure where I am going wrong. Can you help me? L=.144
To find the molar mass of the gas, we need to use the ideal gas law equation:
PV = nRT
Where:
P = Pressure in atm
V = Volume in liters
n = Number of moles
R = Ideal gas constant (0.0821 L·atm/(mol·K))
T = Temperature in Kelvin
First, let's convert the given values to the proper units:
Given:
Pressure (P) = 720 mmHg
Volume (V) = 144 mL
Temperature (T) = 31 degrees Celsius
Conversion:
1 atm = 760 mmHg
1 L = 1000 mL
Temperature in Kelvin (T) = 273 + temperature in Celsius
Now, let's convert the values:
Pressure (P) = 720 mmHg ÷ 760 mmHg/atm = 0.947 atm
Volume (V) = 144 mL ÷ 1000 mL/L = 0.144 L
Temperature (T) = 31°C + 273 = 304 K
Now, we can plug these values into the ideal gas law equation:
0.947 atm × 0.144 L = n × 0.0821 L·atm/(mol·K) × 304 K
Solve for n (the number of moles):
0.136968 = n × 24.9344
n = 0.136968 ÷ 24.9344
n = 0.0055 moles
Finally, to find the molar mass, we divide the mass of the sample by the number of moles:
Molar mass = mass / moles
Molar mass = 0.173 g / 0.0055 mol
Molar mass ≈ 31.455 g/mol
Therefore, the molar mass of the gas sample is approximately 31.455 g/mol.