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Ch.10 - Gases
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.10 - GasesProblem 72a2
Chapter 10, Problem 72a2

(a) What are the mole fractions of N2 in a mixture of 15.08 g of O2, 8.17 g of N2, and 2.64 g of H2?

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Calculate the molar mass of each gas: O_2, N_2, and H_2.
Convert the mass of each gas to moles using the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Sum the moles of all gases to find the total moles in the mixture.
Calculate the mole fraction of N_2 using the formula: \( \text{mole fraction of N}_2 = \frac{\text{moles of N}_2}{\text{total moles}} \).
Express the mole fraction as a decimal.

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Key Concepts

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

Mole Fraction

Mole fraction is a way of expressing the concentration of a component in a mixture. It is defined as the ratio of the number of moles of a specific component to the total number of moles of all components in the mixture. This dimensionless quantity helps in understanding the composition of gas mixtures and is crucial for calculations involving partial pressures and gas laws.
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Calculating Moles from Mass

To find the mole fraction, one must first convert the mass of each gas into moles using the formula: moles = mass (g) / molar mass (g/mol). The molar mass is a characteristic property of each substance, allowing for the determination of how many moles are present in a given mass. This step is essential for accurately calculating the mole fractions of the gases in the mixture.
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Total Moles in a Mixture

The total number of moles in a mixture is the sum of the moles of all individual components. Once the moles of each gas are calculated, they are added together to find the total moles. This total is necessary for determining the mole fraction of each component, as it serves as the denominator in the mole fraction formula, ensuring that the fractions represent the correct proportions of each gas in the mixture.
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Related Practice
Textbook Question

A sample of 5.00 mL of diethyl ether (C2H5OC2H5,density=0.7134 g/mL) is introduced into a 6.00-L vessel that already contains a mixture of N2 and O2, whose partial pressures are 𝑃N2=0.751atm and 𝑃O2=0.208atm. The temperature is held at 35.0°C, and the diethyl ether totally evaporates. b. Calculate the total pressure in the container.

Textbook Question

At an underwater depth of 250 ft, the pressure is 8.38 atm. What should the mole percent of oxygen be in the diving gas for the partial pressure of oxygen in the mixture to be 0.21 atm, the same as in air at 1 atm?

Textbook Question

(a) What are the mole fractions of H2 in a mixture of 15.08 g of O2, 8.17 g of N2, and 2.64 g of H2?

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Textbook Question

A sample of 3.00 g of SO2(g) originally in a 5.00-L vessel at 21 °C is transferred to a 10.0-L vessel at 26 °C. A sample of 2.35 g of N2(g) originally in a 2.50-L vessel at 20 °C is transferred to this same 10.0-L vessel. (a) What is the partial pressure of SO2(g) in the larger container? (b) What is the partial pressure of N2(g) in this vessel?

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Textbook Question

A quantity of N2 gas originally held at 5.25 atm pressure in a 1.00-L container at 26°C is transferred to a 12.5-L container at 20°C. A quantity of O2 gas originally at 5.25 atm and 26°C in a 5.00-L container is transferred to this same container. What is the total pressure in the new container?

Textbook Question

A rigid vessel containing a 3:1 mol ratio of carbon dioxide and water vapor is held at 200°C where it has a total pressure of 2.00 atm. If the vessel is cooled to 10°C so that all of the water vapor condenses, what is the pressure of carbon dioxide? Neglect the volume of the liquid water that forms on cooling.