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1.80g of an unknown gas at STP fills at 500. mL flask. What is the molar mass of the gas?

User Divey
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1 Answer

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Answer:

0.0401 (3 s.f.)

Step-by-step explanation:

Assuming that the gas is a perfect gas and obeys the ideal gas law,

pV = nRT.

In the above gas law, p stands for pressure, V stands for volume, n stands for the number of moles and T stands for pressure. I will use the R (universal gas constant) value of 0.08206 L·atm/K·mol in the working below.

At Standard Temperature and Pressure (STP), the pressure is at 1 atm and the temperature is at 273.15 K.

pV = nRT

Substitute p= 1 atm, V= 0.5 L, T= 273.15,

1(0.5)= n(0.08206)(273.15)

Solve for n:

n= 44.829378

Number of moles× mw= mass

∴ mw= mass ÷ number of moles

Given that the mass is 1.80 g,

Molar mass of gas

= 1.80 ÷44.829378

= 0.0401 (3 s.f.)

User Umar Arshad
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