A chemist places of an unknown monatomic gas into a flask

CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance

Problem

A chemist places

4.60\,\text{g}

of an unknown monatomic gas into a

3.00\,\text{L}

flask. The flask is sealed and held at a uniform temperature of

27\,^{\circ}\text{C}

. The pressure inside is measured to be

745\,\text{torr}

. Atmospheric pressure is

1.013\times10^{5}\,\text{Pa}

1\,\text{torr}=133\,\text{Pa}

. The universal gas constant is

8.31\,\text{J mol}^{-1}\,\text{K}^{-1}

. (a) Convert the given pressure to pascals and the volume to cubic metres. (b) Determine the number of moles of the gas contained in the flask. (c) Using your result from part (b), calculate the molar mass of the gas sample. (d) The possible identities of the gas are He, Ne, Ar, and Xe. Using your calculated molar mass, identify the most likely gas and justify your choice.

Related theory

Ideal Gas Equation
Gaseous State
States of Matter
Combined gas equation
Ideal Gas Law

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