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Ch.3 - Molecules, Compounds & Chemical Equations
Chapter 3, Problem 127

A metal (M) forms a compound with the formula MCl3. If the compound contains 65.57% Cl by mass, what is the identity of the metal?

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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 identity of the metal in MCl3, we can use the given percent composition of chlorine to determine the molar mass of the entire compound and subsequently the molar mass of the metal.
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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 relate the mass of chlorine in MCl3 to the mass of the metal. By using the formula and the known mass percentages, we can set up equations to solve for the molar mass of the metal.
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Periodic Table and Element Identification

The periodic table organizes elements based on their atomic number and properties. Once we calculate the molar mass of the metal from the stoichiometric calculations, we can compare it to known atomic masses of elements in the periodic table to identify the metal. This step is crucial for determining which metal corresponds to the calculated molar mass.
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