Textbook Question
(b) If Ksp = 1.1 * 10-12 for Ag2CrO4, what are the molar concentrations of Ag+ and CrO4 2-in solution?
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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 144
An unknown metal (M) was found not to react with either water or steam, but its reactivity with aqueous acid was not investigated. When a 1.000 g sample of the metal was burned in oxygen and the resulting metal oxide converted to a metal sulfide, 1.504 g of sulfide was obtained. What is the identity of the metal?
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Determine the mass of sulfur in the metal sulfide by subtracting the mass of the metal from the mass of the metal sulfide.
Calculate the moles of sulfur using its molar mass (32.07 g/mol).
Assume the metal forms a simple sulfide (MS) and calculate the moles of the metal using the stoichiometry of the reaction.
Use the initial mass of the metal and the moles of the metal to calculate the molar mass of the metal.
Compare the calculated molar mass with known molar masses of metals to identify the metal.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Metal Reactivity
The reactivity of metals varies significantly, with some metals being highly reactive with water and acids, while others are inert. Metals like alkali metals react vigorously with water, whereas noble metals like gold and platinum do not react at all. Understanding the reactivity series helps predict how a metal will behave in different chemical environments, which is crucial for identifying the unknown metal in this scenario.
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03:12
Transition Metals
Stoichiometry
Stoichiometry involves the calculation of reactants and products in chemical reactions based on the conservation of mass. In this case, knowing the mass of the metal sulfide produced allows for the determination of the moles of sulfur and the unknown metal. This quantitative relationship is essential for deducing the identity of the metal by comparing the molar ratios in the reaction.
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01:16Stoichiometry Concept
Metal Oxides and Sulfides
Metal oxides are compounds formed when metals react with oxygen, while metal sulfides are formed when metals react with sulfur. The transformation from metal oxide to metal sulfide involves a reduction process, where the metal oxide is converted to sulfide, often through a reaction with a sulfide source. Understanding these compounds and their formation is key to analyzing the data provided and identifying the unknown metal.
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Related Practice
Textbook Question
A 100.0 mL solution containing aqueous HCl and HBr was titrated with 0.1235 M NaOH. The volume of base required to neutralize the acid was 47.14 mL. Aqueous AgNO3 was then added to precipitate the Cl-and Br-ions as AgCl and AgBr. The mass of the silver halides obtained was 0.9974 g. What are the molarities of the HCl and HBr in the original solution?
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Textbook Question
A sample of metal (M) reacted with both steam and aqueous HCl to release H2 but did not react with water at room tem-perature. When 1.000 g of the metal was burned in oxygen, it formed 1.890 g of a metal oxide, M2O3. What is the iden-tity of the metal?
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Textbook Question
A mixture of acetic acid (CH3CO2H; monoprotic) and oxalic acid (H2C2O4; diprotic) requires 27.15 mL of 0.100 M NaOH to neutralize it. When an identical amount of the mixture is titrated, 15.05 mL of 0.0247 M KMnO4 is needed for complete reaction. What is the mass percent of each acid in the mixture? (Acetic acid does not react with MnO4 equation for the reaction of oxalic acid with MnO4 given in Problem 4.133.)
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Textbook Question
Iron content in ores can be determined by a redox procedure in which the sample is first reduced with Sn2+, as in Problem 4.130, and then titrated with KMnO4 to oxidize the Fe2+ to Fe3+. The balanced equation is
What is the mass percent Fe in a 2.368 g sample if 48.39 mL of a 0.1116 M KMnO4 solution is needed to titrate the Fe3 + ?
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Textbook Question
A mixture of FeCl2 and NaCl is dissolved in water, and addi-tion of aqueous silver nitrate then yields 7.0149 g of a pre-cipitate. When an identical amount of the mixture is titrated with MnO4 -, 14.28 mL of 0.198 M KMnO4 is needed for complete reaction. What are the mass percents of the two compounds in the mixture? (Na+ and Cl-do not react with MnO4 -. The equation for the reaction of Fe2+ with MnO4 was given in Problem 4.146.)
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