A glass vessel fitted with a stopcock valve has a mass of 337.428 g when evacuated. When filled with Ar, it has a mass of 339.854 g. When evacuated and refilled with a mixture of Ne and Ar, under the same conditions of temperature and pressure, it has a mass of 339.076 g. What is the mole percent of Ne in the gas mixture?

Verified step by step guidance

Calculate the mass of Ar in the vessel by subtracting the mass of the evacuated vessel from the mass of the vessel filled with Ar: 339.854 g - 337.428 g.

Calculate the mass of the Ne and Ar mixture by subtracting the mass of the evacuated vessel from the mass of the vessel filled with the mixture: 339.076 g - 337.428 g.

Determine the mass of Ne in the mixture by subtracting the mass of Ar (from step 1) from the mass of the Ne and Ar mixture (from step 2).

Use the molar masses of Ne (20.18 g/mol) and Ar (39.95 g/mol) to convert the masses of Ne and Ar to moles.

Calculate the mole percent of Ne in the mixture by dividing the moles of Ne by the total moles of Ne and Ar, then multiply by 100 to get the percentage.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of a gas through the equation PV = nRT. This law is fundamental in understanding gas behavior under varying conditions and is essential for calculating the number of moles present in a gas mixture, which is necessary for determining mole percentages.

Mass and Molar Mass

Mass and molar mass are critical for converting between the mass of a substance and the number of moles. The molar mass of each gas (argon and neon) allows for the calculation of the number of moles present in the gas mixture based on the mass measurements provided, which is key to finding the mole percent of neon.

Mole Percent Calculation

Mole percent is a way to express the concentration of a component in a mixture, calculated as the number of moles of that component divided by the total number of moles of all components, multiplied by 100. Understanding this concept is crucial for determining the composition of the gas mixture in the question, specifically the proportion of neon relative to argon.

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