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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 97

A compound, Na2Cr2Ox, where x is unknown, is analyzed and found to contain 39.70% Cr. What is the value of x?

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Key Concepts

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

Molar Mass and Percent Composition

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole. Percent composition refers to the percentage by mass of each element in a compound. To find the unknown 'x' in Na2Cr2Ox, we need to use the percent composition of chromium (Cr) to relate it to the total molar mass of the compound.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the conservation of mass. In this context, it allows us to set up a relationship between the moles of chromium and the total moles of the compound, helping to determine the unknown variable 'x' by using the known percentage of chromium.
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Empirical Formula

The empirical formula represents the simplest whole-number ratio of elements in a compound. By determining the moles of each element in Na2Cr2Ox based on the percent composition, we can derive the empirical formula, which will help us find the value of 'x' by ensuring the ratio of sodium, chromium, and oxygen is consistent with the given data.
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Related Practice
Textbook Question
The fluoride ion reacts with water to produce HF. (a) Write out the chemical equation for this reaction.
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Textbook Question

Vanillin, the dominant flavoring in vanilla, contains C, H, and O. When 1.05 g of this substance is completely combusted, 2.43 g of CO2 and 0.50 g of H2O are produced. What is the empirical formula of vanillin?

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Textbook Question

An organic compound was found to contain only C, H, and Cl. When a 1.50-g sample of the compound was completely combusted in air, 3.52 g of CO2 was formed. In a separate experiment, the chlorine in a 1.00-g sample of the compound was converted to 1.27 g of AgCl. Determine the empirical formula of the compound.

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Textbook Question

An element X forms an iodide 1XI32 and a chloride 1XCl32. The iodide is quantitatively converted to the chloride when it is heated in a stream of chlorine: 2 XI3 + 3 Cl2¡2 XCl3 + 3 I2 If 0.5000 g of XI3 is treated with chlorine, 0.2360 g of XCl3 is obtained. (a) Calculate the atomic weight of the element X.

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Textbook Question

A method used by the U.S. Environmental Protection Agency (EPA) for determining the concentration of ozone in air is to pass the air sample through a 'bubbler' containing sodium iodide, which removes the ozone according to the following equation: O31g2 + 2 NaI1aq2 + H2O1l2¡ O21g2 + I21s2 + 2 NaOH1aq2 (a) How many moles of sodium iodide are needed to remove 5.95 * 10-6 mol of O3?

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Textbook Question

A method used by the U.S. Environmental Protection Agency (EPA) for determining the concentration of ozone in air is to pass the air sample through a 'bubbler' containing sodium iodide, which removes the ozone according to the following equation: O31g2 + 2 NaI1aq2 + H2O1l2¡ O21g2 + I21s2 + 2 NaOH1aq2 (b) How many grams of sodium iodide are needed to remove 1.3 mg of O3?

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