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Ch.10 - Gases
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 15th EditionCh.10 - GasesProblema 53
Capitolo 10, Problema 53

In the Dumas-bulb technique for determining the molar mass of an unknown liquid, you vaporize the sample of a liquid that boils below 100°C in a boiling-water bath and determine the mass of vapor required to fill the bulb. From the following data, calculate the molar mass of the unknown liquid: mass of unknown vapor, 1.012 g; volume of bulb, 354 cm3; pressure, 742 torr; temperature, 99°C.

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Convert the pressure from torr to atm using the conversion factor: 1 atm = 760 torr.
Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature.
Convert the volume from cm³ to liters by dividing by 1000, since 1 L = 1000 cm³.
Use the ideal gas law equation, PV = nRT, to solve for the number of moles (n) of the vapor. Here, P is the pressure in atm, V is the volume in liters, R is the ideal gas constant (0.0821 L·atm/mol·K), and T is the temperature in Kelvin.
Calculate the molar mass of the unknown liquid by dividing the mass of the vapor (in grams) by the number of moles (n) obtained from the ideal gas law calculation.

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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. In this context, it allows us to calculate the number of moles of vapor produced from the unknown liquid, which is essential for determining its molar mass.
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01:15
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 find the molar mass of the unknown liquid, we use the formula: Molar Mass = mass of vapor (g) / moles of vapor (n), where n is derived from the Ideal Gas Law.
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03:12
Molar Mass Calculation Example

Conversions and Units

Understanding unit conversions is crucial in this problem, particularly converting pressure from torr to atmospheres and temperature from Celsius to Kelvin. Accurate conversions ensure that the calculations align with the standard units used in the Ideal Gas Law, leading to correct results.
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01:56
Conversion Factors
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