Problem: A sample of gas has a mass of 38.8 mg . Its volume is 226 mL at a temperature of 56 oC and a pressure of 860 torr .Find the molar mass of the gas.

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


Step1: 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

A sample of gas has a mass of 38.8 mg . Its volume is 226 mL at a temperature of 56 oC and a pressure of 860 torr .

Find the molar mass of the gas.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Ideal Gas Law Molar Mass concept. If you need more Ideal Gas Law Molar Mass practice, you can also practice Ideal Gas Law Molar Mass practice problems.