Aevenir V.

# A gas has a density of 0.791 g/L. What is the molar mass of this gas?

I wonder why the formula is m (mass) = p x V (density multiply with volume)

But the answer key of the book is: Molar Mass (M) = g/L × 22.4 L/1 mole = p x V

SO , in this situation , do we find mass = molar mass= p x V ????

Aevenir V.

A gas has a density of 0.791 g/L. What is the molar mass of this gas? (3 points) Selected Answer: Molar mass (gram/moles) = g/L x 22.4 = 0.791 x 22.4 ≈ 17.72 (gram/moles)
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01/04/20

By: Ph.D. in Biochemistry--University Professor--Chemistry Tutor

Aevenir V.

Hi Mr.J.R.S, Thank you so much for your explanation. It is really explicit and meaningful for me. However, I have not studied about the ideal gas law PV = nRT so it is a bit confused for me to understand it. Do you have any simple way that do not need to apply the ideal gas law ? Anyways, I feel so thankful and a lot of thanks, sir !!!
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01/04/20 J.R. S.

tutor
Yes, the simple way is the first way I showed. But you must know the fact that at standard temperature and pressure (STP), 1 mole of a gas equals 22.4 liters. Once you know that (memorize it), you can use the density to find the molar mass. 0.791 g/L and 1 mole = 22.4 liter, so you have 0.791 g/L x 22.4 L/1 mole = 17.7 g/mole. Answer.
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01/04/20 Barry M.

tutor
Note that the symbol for density is the Greek letter rho, which resembles p. Also, in case you forget 22.4 but remember PV = nRT, and the value of R, you can solve for V = nRT/P, and since n = 1 for 1 mole, and P = 1 for 1 atm, V = RT = 0.0821 X 273 = 22.4
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01/05/20

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