A 1L flask is filled with 1.25 g of argon at 25 degrees celcium. A sample of ethane vapor is added to the same flask until the total pressure is 1.45 atm.
What is the partial pressure of argon in the flask?
Chemistry - DrBob222, Tuesday, October 5, 2010 at 9:00pm
mols Ar = 1.25/39.95 = 0.0313
Use PV = nRT to calculate pressure Ar.
Remember that the partial pressure of a gas doesn't depend upon what other gas is present. In effect, we ignore the ethane vapor although the partial pressure of the ethane COULD be calculated, also.
How to calculate partial pressure of the ethane.
Ptotal = 1.45 = pAr + pethane
You know Ptotal and pAr, calculate p ethane.
.20
To calculate the partial pressure of ethane, you would need to know the number of moles of ethane present in the flask. However, this information is not provided in the question. Therefore, we cannot calculate the partial pressure of ethane in this case.
Only the partial pressure of argon is asked for in the question, so we can focus on calculating that.
To calculate the partial pressure of argon in the flask, we can use the ideal gas law equation, PV = nRT.
Given:
- Volume (V) = 1 L
- Total pressure (P) = 1.45 atm
- Temperature (T) = 25 degrees Celsius (which needs to be converted to Kelvin, by adding 273.15)
From the given mass of argon (1.25 g), we can calculate the number of moles by dividing the mass by the molar mass of argon (39.95 g/mol).
moles Ar = mass Ar / molar mass Ar
= 1.25 g / 39.95 g/mol
Now that we have the moles of argon, we can substitute these values into the ideal gas law equation and solve for the partial pressure of argon (PAr).
PAr x V = n Ar x R x T
Substituting the known values:
PAr x 1 L = 0.0313 mol x R x (25 + 273.15) K
PAr = (0.0313 mol x R x 298.15 K) / 1 L
PAr = (0.0313 mol x R x 298.15 K) (since the volume is 1 L)
Now, we need to know the value of the gas constant (R) for the units we are using. The ideal gas constant, R, can be approximated to 0.0821 L·atm/(mol·K).
PAr = (0.0313 mol x 0.0821 L·atm/(mol·K) x 298.15 K) / 1 L
Calculating the above expression will give us the partial pressure of argon in the flask.