A gas mixture is made by combining 7.2 g each of Ar, Ne, and an unknown diatomic gas. At STP, the mixture occupies a volume of 14.30 L. What is the molar mass of the unknown gas? Identify the unknown gas.
A mole of gas has a volume of 22.4Lat STP.Now find the total moles of gas in the mixture by (14.30)/(22.4).
And you know the molar masses of At and Ne.you can find the moles of At and Ne as follows:
Moles of Ar =(7.2)g/(molar mass of Ar)gmol-1
Moles of Ne=7.2g/(molar mass of Ne)gmol-1
Now substrct the sum of moles of Ar and Ne from the total moles.There you get the moles of unknow diatomic gas.Then you can find its molar mass
mols Ar = grams/molar mass = ?
mols Ne = grams/molar mass = ?
mols unk = grams/molar mass but you don't know the molar mass of this; therefore, you can't calculate this at this point.
total mols = mols Ar + mols Ne + mols unk.
Use PV = nRT to calculate total mols.
Then mols unk = total mols - mols Ar - mols Ne.
Finally, mols unk = grams/molar mass. You know mol unk and grams unk, solve for molar mass unk. Post your work if you get stuck.
Thank you both!
DrBob222 just saw your answer to this question.can I know whether my method of solving is correct or not? Thank you..
To find the molar mass of the unknown gas, we need to use the ideal gas law equation:
PV = nRT
Where:
P = pressure (at STP, the pressure is 1 atm)
V = volume (14.30 L)
n = number of moles
R = ideal gas constant (0.0821 L·atm/mol·K)
T = temperature (at STP, the temperature is 273.15 K)
First, let's determine the number of moles of argon (Ar), neon (Ne), and the unknown gas present in the mixture.
For argon:
The molar mass of Ar is 39.95 g/mol
The number of moles of Ar can be calculated using the formula:
number of moles = mass / molar mass
number of moles of Ar = 7.2 g / 39.95 g/mol = 0.18045 mol
For neon:
The molar mass of Ne is 20.18 g/mol
The number of moles of Ne can be calculated using the formula:
number of moles = mass / molar mass
number of moles of Ne = 7.2 g / 20.18 g/mol = 0.35676 mol
To find the number of moles of the unknown gas, we subtract the moles of argon and neon from the total moles of the mixture:
Number of moles of the unknown gas = Total moles - moles of Ar - moles of Ne
Total moles = moles of Ar + moles of Ne
Total moles = 0.18045 mol + 0.35676 mol = 0.53721 mol
Number of moles of the unknown gas = 0.53721 mol - 0.18045 mol - 0.35676 mol = 0.0 mol
Since the number of moles of the unknown gas is zero, it means that there is no unknown gas present in the mixture. Therefore, the molar mass of the unknown gas cannot be determined, and the identity of the unknown gas is unknown.