When 2.876 g of a certain metal sulfide is roasted in air, 2.368 g of the metal oxide is forme

step 1 an element that can readily form positive ions. These are identified as cat ions and has metalli

When 2.876 g of a certain metal sulfide is roasted in air,...

Key Concepts

Molar Mass Determination

Determining the molar mass of a substance involves connecting the experimental mass data with the mole concept and the known compositions of compounds. By comparing the mass ratios of the metal in different compounds (sulfide and oxide) and using the formulas implied by their oxidation states, one can solve for the unknown molar mass of the metal.

Oxidation Numbers

Oxidation numbers are used to determine the charges on atoms within compounds and to infer their chemical formulas, especially for ionic compounds. Knowing that the metal has an oxidation number of +2 helps to deduce the likely formulas of the metal sulfide and oxide, as the anions must balance this charge, guiding the stoichiometric analysis.

Conservation of Mass

The law of conservation of mass is fundamental in chemical reactions; it states that the total mass of the reactants must equal the total mass of the products. In this context, even though the compound changes form during roasting, the mass of the metal remains unchanged. This principle is essential for determining the metal’s fraction in both the starting sulfide and the resulting oxide.

Stoichiometry

This concept involves using the quantitative relationships between reactants and products in a chemical reaction. In problems like this, stoichiometry allows us to determine how the amount of one substance relates to the amount of another, based on their chemical formulas and the balanced reaction, enabling us to set up equations that interconnect the masses and moles of the substances involved.

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