Problem: An unknown gas contained in a 1.85 L flask is weighed and found to have a mass of 15.87 g at a pressure of 2.45 atm and a temperature of 18.6°C. What is the molecular weight of the gas?a. 5.35 g/molb. 83.8 g/molc. 1.14 g/mold. 155 g/mole. 77.1 g/mol

🤓 Based on our data, we think this question is relevant for Professor Bindell's class at UCF.

FREE Expert Solution
FREE Expert Solution

We’re being asked to determine the molecular weight of the unknown gas. 

Recall that molecular weight is in grams per 1 mole of a substance.

Molecular Weight (MW)=gmol


First, we have to calculate the amount of gas in moles using the ideal gas equation.

PV=nRT

P = pressure, atm
V = volume, L
n = moles, mol
R = gas constant = 0.08206 (L·atm)/(mol·K)
T = temperature, K


Isolate n (number of moles of gas): 

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Problem Details

An unknown gas contained in a 1.85 L flask is weighed and found to have a mass of 15.87 g at a pressure of 2.45 atm and a temperature of 18.6°C. What is the molecular weight of the gas?

a. 5.35 g/mol

b. 83.8 g/mol

c. 1.14 g/mol

d. 155 g/mol

e. 77.1 g/mol

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Based on our data, we think this problem is relevant for Professor Bindell's class at UCF.