Problem: Calculate the molar mass of a gas if 2.50 g occupies 0.875 L at 685 Torr and 35°C.(a) 0.106 g/mole (b) 28.1 g/mole (c) 9.12 g/mole(d) 32.0 g/mole (e) 80.1 g/mole

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

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

Calculate the molar mass of a gas if 2.50 g occupies 0.875 L at 685 Torr and 35°C.

(a) 0.106 g/mole 

(b) 28.1 g/mole 

(c) 9.12 g/mole

(d) 32.0 g/mole 

(e) 80.1 g/mole

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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.

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