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Arsenic(III) sulfide sublimes readily, even below its melting point of \(320^{\circ} \mathrm{C}\). 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?

Short Answer

Expert verified
The molecular formula of arsenic(III) sulfide in the gas phase is \( \text{As}_4\text{S}_6 \).

Step by step solution

01

Understand the Problem

We are given that arsenic(III) sulfide sublimes and its vapor effusion rate is 0.52 times that of xenon (Xe). We need to find the molecular formula of arsenic(III) sulfide in the gas phase.
02

Apply Graham's Law of Effusion

Graham's Law of Effusion states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass: \( \frac{r_1}{r_2} = \sqrt{\frac{M_2}{M_1}} \). Here, \( r_1 \) and \( r_2 \) are the rates of effusion, and \( M_1 \) and \( M_2 \) are the respective molar masses of Xe and arsenic(III) sulfide vapor.
03

Set Up the Effusion Rate Ratio

We know that the rate of effusion of arsenic(III) sulfide is 0.52 times that of Xe, so \( \frac{r_{\text{As}_x \text{S}_y}}{r_{\text{Xe}}} = 0.52 \). Let \( M_{\text{As}_x \text{S}_y} \) be the molar mass of arsenic(III) sulfide and \( M_{\text{Xe}} \), the molar mass of xenon (131.29 g/mol).
04

Substitute and Solve the Equation

Using \( \frac{r_{\text{As}_x \text{S}_y}}{r_{\text{Xe}}} \), the equation from Graham's Law becomes \( 0.52 = \sqrt{\frac{M_{\text{Xe}}}{M_{\text{As}_x \text{S}_y}}} \). Squaring both sides gives \( 0.2704 = \frac{M_{\text{Xe}}}{M_{\text{As}_x \text{S}_y}} \), so \( M_{\text{As}_x \text{S}_y} = \frac{M_{\text{Xe}}}{0.2704} \).
05

Calculate Molar Mass of Arsenic(III) Sulfide

Calculate the molar mass: \( M_{\text{As}_x \text{S}_y} = \frac{131.29}{0.2704} = 485.5 \text{ g/mol} \).
06

Determine the Molecular Formula

The molar mass of arsenic is approximately 74.92 g/mol, and sulfur is approximately 32.06 g/mol. Assume \( x \) arsenic atoms and \( y \) sulfur atoms: \( 74.92x + 32.06y = 485.5 \). Checking combinations, an approximate match is reached with \( x = 4 \) and \( y = 6 \), which matches the total molar mass.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Effusion
Effusion is the process by which gas molecules escape through a tiny opening into a vacuum or a less pressurized environment. It's a fascinating phenomenon that plays a key role in understanding how gases behave. In simple terms, effusion rates are influenced by the size of the gas molecules and their speeds. According to Graham's Law of Effusion, the rate of effusion of a gas is inversely proportional to the square root of its molar mass. So, lighter gases effuse faster than heavier ones.

Graham's Law can be mathematically expressed as: \[\frac{r_1}{r_2} = \sqrt{\frac{M_2}{M_1}}\]Here, \( r_1 \) and \( r_2 \) are the rates of effusion, while \( M_1 \) and \( M_2 \) represent the molar masses of the two gases being compared. Applying this concept helps us determine unknown molecular masses when we know how two gases effuse relative to each other.
Molecular formula determination
Determining the molecular formula of a compound often involves some detective work. It's like piecing together a puzzle by finding how atoms fit into a specific combination based on their mass and the data we have.In our scenario, we had to find the molecular formula of arsenic(III) sulfide in the gaseous state, knowing that its effusion rate is 0.52 times that of xenon (Xe) under similar conditions. Using Graham's Law, we were able to calculate the molar mass of the gaseous arsenic(III) sulfide.The molar mass we obtained was 485.5 g/mol. With the approximate atomic masses of arsenic (74.92 g/mol) and sulfur (32.06 g/mol), the task became to find integer values for \( x \) and \( y \), such that the equation \( 74.92x + 32.06y = 485.5 \) holds true. Through a trial-and-error approach, or simply guessing and checking logical combinations, we discovered that 4 arsenic atoms and 6 sulfur atoms meet this requirement. Thus, the molecular formula was deduced to be As4S6.
Arsenic(III) sulfide
Arsenic(III) sulfide, also known as orpiment, is a fascinating compound. Its chemical formula in solid form is typically As4S4, but it can exhibit different structures in vapor. Arsenic(III) sulfide is characterized by its striking yellow hue and has been historically used in art and manufacturing. One unique property of arsenic(III) sulfide is its ability to sublime below its melting point of 320°C. Sublimation is a phase transition where a substance goes from solid to gas without passing through a liquid phase, often seen in substances like dry ice. This compound is particularly interesting for study because of its ability to exist in multiple forms, both in consistency and molecular arrangement. Understanding how it behaves in different phases enhances our comprehension of molecular behavior and effusion dynamics.

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Most popular questions from this chapter

A \(6.53-g\) sample of a mixture of magnesium carbonate and calcium carbonate is treated with excess hydrochloric acid. The resulting reaction produces \(1.72 \mathrm{~L}\) of carbon dioxide gas at \(28^{\circ} \mathrm{C}\) and \(99.06 \mathrm{kPa}\) pressure. (a) Write balanced chemical equations for the reactions that occur between hydrochloric acid and each component of the mixture. (b) Calculate the total number of moles of carbon dioxide that forms from these reactions. (c) Assuming that the reactions are complete, calculate the percentage by mass of magnesium carbonate in the mixture.

Indicate which of the following statements regarding the kinetic-molecular theory of gases are correct. (a) The average kinetic energy of a collection of gas molecules at a given temperature is proportional to \(m^{1 / 2} \cdot(\mathbf{b})\) The gas molecules are assumed to exert no forces on each other. (c) All the molecules of a gas at a given temperature have the same kinetic energy. (d) The volume of the gas molecules is negligible in comparison to the total volume in which the gas is contained. (e) All gas molecules move with the same speed if they are at the same temperature.

Imagine that the reaction \(2 \mathrm{CO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)\) occurs in a container that has a piston that moves to maintain a constant pressure when the reaction occurs at constant temperature. Which of the following statements describes how the volume of the container changes due to the reaction: (a) the volume increases by \(50 \%,(\mathbf{b})\) the volume increases by \(33 \%\), (c) the volume remains constant, (d) the volume decreases by \(33 \%,(\mathbf{e})\) the volume decreases by \(50 \% .\)

Rank the following gases and vapors from least dense to most dense at \(101.33 \mathrm{kPa}\) and \(298 \mathrm{~K}:\) water vapor \(\left(\mathrm{H}_{2} \mathrm{O}(g)\right),\) nitrogen \(\left(\mathrm{N}_{2}\right),\) hydrogen sulfide \(\left(\mathrm{H}_{2} \mathrm{~S}\right)\)

A rigid vessel containing a \(3: 1 \mathrm{~mol}\) ratio of carbon dioxide and water vapor is held at \(200^{\circ} \mathrm{C}\) where it has a total pressure of \(202.7 \mathrm{kPa}\). If the vessel is cooled to \(10^{\circ} \mathrm{C}\) 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.

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