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Ch.5 - Gases
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoTro 4th EditionCh.5 - GasesProblema 97
Capitolo 5, Problema 97

The mass of an evacuated 255 mL flask is 143.187 g. The mass of the flask filled with 267 torr of an unknown gas at 25 °C is 143.289 g. Calculate the molar mass of the unknown gas.

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Calculate the mass of the unknown gas by subtracting the mass of the evacuated flask from the mass of the flask filled with the gas: \( \text{mass of gas} = 143.289 \text{ g} - 143.187 \text{ g} \).
Convert the pressure from torr to atm using the conversion factor: \( 1 \text{ atm} = 760 \text{ torr} \).
Convert the temperature from Celsius to Kelvin using the formula: \( T(\text{K}) = T(\text{°C}) + 273.15 \).
Use the ideal gas law \( PV = nRT \) to solve for the number of moles \( n \) of the gas, where \( P \) is the pressure in atm, \( V \) is the volume in liters, \( R \) is the ideal gas constant \( 0.0821 \text{ L atm mol}^{-1} \text{ K}^{-1} \), and \( T \) is the temperature in Kelvin.
Calculate the molar mass of the gas using the formula: \( \text{Molar mass} = \frac{\text{mass of gas}}{n} \), where \( n \) is the number of moles calculated in the previous step.

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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 essential for understanding how gases behave under different conditions and is used to derive the molar mass of a gas when its pressure, volume, and temperature are known.
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Ideal Gas Law Formula

Molar Mass Calculation

Molar mass is defined as the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the molar mass of the unknown gas, the mass difference between the empty flask and the flask filled with gas is divided by the number of moles of gas, which can be determined using the Ideal Gas Law.
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Molar Mass Calculation Example

Gas Density

Gas density is the mass of a gas per unit volume, often expressed in grams per liter (g/L). In this problem, the density of the unknown gas can be derived from the mass of the gas and the volume of the flask, which is crucial for calculating the molar mass using the relationship between density, molar mass, and the Ideal Gas Law.
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Percorso guidato
01:21
Gas Density Example
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