Skip to main content
Ch.10 - Gases
Chapter 10, Problem 85

Hydrogen has two naturally occurring isotopes, 1H and 2H. Chlorine also has two naturally occurring isotopes, 35Cl and 37Cl. Thus, hydrogen chloride gas consists of four distinct types of molecules: 1H35Cl, 1H37Cl, 2H35Cl, and 2H37Cl. Place these four molecules in order of increasing rate of effusion.

Verified step by step guidance
1
Identify the concept of effusion, which is the process by which gas molecules escape through a small hole into a vacuum.
Recall Graham's law of effusion, which states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass: \( \text{Rate} \propto \frac{1}{\sqrt{M}} \).
Calculate the molar mass of each molecule: \( ^1\text{H}^{35}\text{Cl} \), \( ^1\text{H}^{37}\text{Cl} \), \( ^2\text{H}^{35}\text{Cl} \), and \( ^2\text{H}^{37}\text{Cl} \).
Compare the molar masses: the molecule with the smallest molar mass will have the highest rate of effusion, and the one with the largest molar mass will have the lowest rate of effusion.
Arrange the molecules in order of increasing molar mass, which will correspond to increasing rate of effusion.

Recommended similar problem, with video answer:

Verified Solution

This video solution was recommended by our tutors as helpful for the problem above
Video duration:
3m
Was this helpful?

Key Concepts

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

Effusion

Effusion is the process by which gas molecules escape from a container through a small opening. The rate of effusion is influenced by the mass of the gas molecules; lighter molecules effuse faster than heavier ones. This principle is described by Graham's law, which states that the rate of effusion is inversely proportional to the square root of the molar mass of the gas.
Recommended video:
Guided course
01:31
Effusion Rate Example

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For example, hydrogen has isotopes 1H (protium) and 2H (deuterium), while chlorine has 35Cl and 37Cl. The presence of isotopes affects the molar mass of compounds formed, which in turn influences their rates of effusion.
Recommended video:

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). In the context of the question, the molar mass of hydrogen chloride molecules varies based on the isotopes of hydrogen and chlorine present. The different combinations of isotopes lead to distinct molar masses, which are crucial for determining the order of effusion rates among the four types of hydrogen chloride molecules.
Recommended video:
Guided course
02:11
Molar Mass Concept
Related Practice
Textbook Question

(c) Calculate the most probable speeds of Cl2 molecules at 300 K.

131
views
Textbook Question

Which one or more of the following statements are true? (a) O2 will effuse faster than Cl2. (b) Effusion and diffusion are different names for the same process. (c) Perfume molecules travel to your nose by the process of effusion. (d) The higher the density of a gas, the shorter the mean free path.

1028
views
Textbook Question

At constant pressure, the mean free path 1l2 of a gas molecule is directly proportional to temperature. At constant temperature, l is inversely proportional to pressure. If you compare two different gas molecules at the same temperature and pressure, l is inversely proportional to the square of the diameter of the gas molecules. Put these facts together to create a formula for the mean free path of a gas molecule with a proportionality constant (call it Rmfp, like the ideal-gas constant) and define units for Rmfp.

951
views
Open Question
As discussed in the “Chemistry Put to Work” box in Section 10.8, enriched uranium can be produced by effusion of gaseous UF6 across a porous membrane. Suppose a process were developed to allow effusion of gaseous uranium atoms, U(g). Calculate the ratio of effusion rates for 235U and 238U, and compare it to the ratio for UF6 given in the essay.
Textbook Question

Arsenic(III) sulfide sublimes readily, even below its melting point of 320 °C. The molecules of the vapor phase are found to effuse through a tiny hole at 0.52 times the rate of effusion of Xe atoms under the same conditions of temperature and pressure. What is the molecular formula of arsenic(III) sulfide in the gas phase?

1628
views
Textbook Question

A gas of unknown molecular mass was allowed to effuse through a small opening under constant-pressure conditions. It required 105 s for 1.0 L of the gas to effuse. Under identical experimental conditions it required 31 s for 1.0 L of O2 gas to effuse. Calculate the molar mass of the unknown gas. (Remember that the faster the rate of effusion, the shorter the time required for effusion of 1.0 L; in other words, rate is the amount that diffuses over the time it takes to diffuse.)

1825
views