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Ch.15 - Chemical Equilibrium
All textbooksBrown 14th EditionCh.15 - Chemical EquilibriumProblem 76c
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Chapter 15, Problem 76c

A sample of nitrosyl bromide (NOBr) decomposes according to the equation 2 NOBr(𝑔) β‡Œ 2 NO(𝑔) + Br2(𝑔) An equilibrium mixture in a 5.00-L vessel at 100Β°C contains 3.22 g of NOBr, 3.08 g of NO, and 4.19 g of Br2. (c) What was the mass of the original sample of NOBr?

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1
Calculate the molar mass of NOBr using the atomic masses of nitrogen (N), oxygen (O), and bromine (Br).
Convert the given mass of NOBr at equilibrium (3.22 g) to moles using its molar mass.
Convert the given masses of NO (3.08 g) and Br<sub>2</sub> (4.19 g) to moles using their respective molar masses.
Use the stoichiometry of the balanced equation 2 NOBr β‡Œ 2 NO + Br<sub>2</sub> to determine the moles of NOBr that decomposed to form the moles of NO and Br<sub>2</sub> at equilibrium.
Add the moles of NOBr at equilibrium to the moles of NOBr that decomposed to find the initial moles of NOBr, then convert this back to grams to find the original mass of the NOBr sample.

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Key Concepts

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

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. In this case, the decomposition of nitrosyl bromide (NOBr) involves a specific molar ratio of reactants to products, which is essential for determining the amounts of substances involved in the reaction.
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Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. Understanding equilibrium is crucial for analyzing the decomposition of NOBr, as it helps in determining how much of the original sample remains and how much has reacted at a given time.
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Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole. To find the mass of the original sample of NOBr, it is necessary to calculate the number of moles present in the equilibrium mixture using the molar mass of NOBr, which allows for the determination of the initial mass before decomposition.
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Textbook Question

When 2.00 mol of SO2Cl2 is placed in a 2.00-L flask at 303 K, 56% of the SO2Cl2 decomposes to SO2 and Cl2: SO2Cl2(𝑔) β‡Œ SO2(𝑔) + Cl2(𝑔) (c) According to Le ChΓ’telier's principle, would the percent of SO2Cl2 that decomposes increase, decrease or stay the same if the mixture were transferred to a 15.00-L vessel?

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Open Question
The value of the equilibrium constant Kc for the reaction N2(g) + 3 H2(g) β‡Œ 2 NH3(g) changes in the following manner as a function of temperature: Temperature (Β°C) Kc 300 9.6 400 0.50 500 0.058. (b) Use the standard enthalpies of formation given in Appendix C to determine the Ξ”H for this reaction at standard conditions. Does this value agree with your prediction from part (a)?
Textbook Question

A sample of nitrosyl bromide (NOBr) decomposes according to the equation 2 NOBr(𝑔) β‡Œ 2 NO(𝑔) + Br2(𝑔) An equilibrium mixture in a 5.00-L vessel at 100Β°C contains 3.22 g of NOBr, 3.08 g of NO, and 4.19 g of Br2. (b) What is the total pressure exerted by the mixture of gases?

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Textbook Question

Consider the hypothetical reaction A(𝑔) β‡Œ 2 B(𝑔). A flask is charged with 0.75 atm of pure A, after which it is allowed to reach equilibrium at 0Β°C. At equilibrium, the partial pressure of A is 0.36 atm. (c) What could we do to maximize the yield of B?

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Textbook Question

As shown in Table 15.2, the equilibrium constant for the reaction N2(𝑔) + 3 H2(𝑔) β‡Œ 2 NH3(𝑔) is 𝐾𝑝 = 4.34Γ—10βˆ’3 at 300Β°C. Pure NH3 is placed in a 1.00-L flask and allowed to reach equilibrium at this temperature. There are 1.05 g NH3 in the equilibrium mixture. (b) What was the initial mass of ammonia placed in the vessel?

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Open Question
For the equilibrium 2 IBr(g) β‡Œ I2(g) + Br2(g), Kp = 8.5 * 10^-3 at 150 _x001F_C. If 0.025 atm of IBr is placed in a 2.0-L container, what is the partial pressure of all substances after equilibrium is reached?