Skip to main content
Ch.10 - Gases
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.10 - GasesProblema 54
Capitolo 10, Problema 54

The molar mass of a volatile substance was determined by the Dumas-bulb method described in Exercise 10.53. The unknown vapor had a mass of 2.55 g; the volume of the bulb was 500 mL, pressure 101.33 kPa, and temperature 37 °C.Calculate the molar mass of the unknown vapor.

Guida verificata passo dopo passo
1
Convert the temperature from Celsius to Kelvin by adding 273.15 to the Celsius temperature.
Convert the volume from milliliters to liters by dividing by 1000.
Use the ideal gas law equation, PV = nRT, to solve for the number of moles (n) of the gas. Here, P is the pressure in kPa, V is the volume in liters, R is the ideal gas constant (8.314 L·kPa/mol·K), and T is the temperature in Kelvin.
Rearrange the ideal gas law equation to solve for n: n = PV / RT.
Calculate the molar mass by dividing the mass of the vapor (2.55 g) by the number of moles (n) calculated in the previous step.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
5m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

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 calculating the molar mass of gases, as it allows us to determine the number of moles (n) from the known values of pressure (P), volume (V), and temperature (T), using the ideal gas constant (R).
Video consigliato:
Percorso guidato
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 calculate the molar mass of a gas using the Ideal Gas Law, we can rearrange the equation to find n (moles) and then use the formula: Molar Mass = mass (g) / n (moles). This allows us to derive the molar mass from the mass of the gas and the conditions under which it was measured.
Video consigliato:
Percorso guidato
03:12
Molar Mass Calculation Example

Dumas Method

The Dumas method is a technique used to determine the molar mass of volatile substances by measuring the mass of vapor produced in a controlled environment. In this method, the vapor is collected in a bulb, and its properties (mass, volume, pressure, and temperature) are measured to apply the Ideal Gas Law, facilitating the calculation of the substance's molar mass.
Video consigliato:
Percorso guidato
01:49
Method 1 of Radioactive Half-Life
Pratica correlata
Domanda del libro di testo
Magnesium can be used as a 'getter' in evacuated enclosures to react with the last traces of oxygen. (The magnesium is usually heated by passing an electric current through a wire or ribbon of the metal.) If an enclosure of 5.67 L has a partial pressure of O2 of 7.066 mPa at 30 °C, what mass of magnesium will react according to the following equation? 2 Mg1s2 + O21g2¡2 MgO1s2
550
views
Domanda del libro di testo
(b) Calculate the molar mass of a vapor that has a density of 7.135 g>L at 12 °C and 99.06 kPa.
1066
views
Domanda del libro di testo
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, 98.93 kPa; temperature, 99 °C.
1232
views
Domanda del libro di testo

(b) Calculate the molar mass of a gas if 2.50 g occupies 0.875 L at 685 torr and 35 °C

977
views
Domanda del libro di testo
Calcium hydride, CaH2, reacts with water to form hydrogen gas: CaH21s2 + 2 H2O1l2¡Ca1OH221aq2 + 2 H21g2 This reaction is sometimes used to inflate life rafts, weather balloons, and the like, when a simple, compact means of generating H2 is desired. How many grams of CaH2 are needed to generate 145 L of H2 gas if the pressure of H2 is 110 kPa at 21 °C?
4120
views