A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO 2 gas. The mass of the copper sulfide produced was 2.748 g. (b) What is its empirical formula?

Hey everyone, welcome back. We're asked to provide the empirical formula for a substance consisting of 1.78g of copper and 2.22g of selenium first. Let's go ahead and convert our grams into moles. Starting off with 1.78 g of copper. We're going to use coppers atomic mass of 63. g per one mole. And when we calculate this out, we end up with a value of 0. mol of copper. Moving on to selenium, we have 2.22g of selenium And we know that selenium is atomic mass is 78.96 g of selenium per one mole. And when we calculate this out, we end up with a total of 0.02, a mole of selenium. And now all we need to do is divide both of our values by the least amount of moles. And in this case since both of our values are 0.028, All we need to do is divide them both by 0.028 which gets us to one of copper and one of selenium. So our empirical formula is going to be C U S E. So I hope this made sense and let us know if you have any questions

Ch.3 - Mass Relationships in Chemical Reactions

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McMurry 8th Edition

Ch.3 - Mass Relationships in Chemical Reactions

Problem 117b

Chapter 3, Problem 117b

A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO₂ gas. The mass of the copper sulfide produced was 2.748 g. (b) What is its empirical formula?

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Determine the mass of sulfur that reacted by subtracting the mass of copper from the mass of copper sulfide: \( \text{mass of sulfur} = \text{mass of copper sulfide} - \text{mass of copper} \).

Convert the mass of copper to moles using its molar mass: \( \text{moles of copper} = \frac{\text{mass of copper}}{\text{molar mass of copper}} \).

Convert the mass of sulfur to moles using its molar mass: \( \text{moles of sulfur} = \frac{\text{mass of sulfur}}{\text{molar mass of sulfur}} \).

Determine the simplest whole number ratio of moles of copper to moles of sulfur by dividing each by the smallest number of moles calculated.

Use the mole ratio to write the empirical formula of the copper sulfide compound.

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Key Concepts

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

Empirical Formula

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is determined by calculating the moles of each element and then dividing by the smallest number of moles to find the simplest ratio. This formula does not provide information about the actual number of atoms in a molecule but rather the relative proportions of each element.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It involves using balanced chemical equations to calculate the amounts of substances consumed and produced. In this context, stoichiometry helps determine the moles of copper and sulfur that reacted to form copper sulfide, which is essential for finding the empirical formula.

Mass Conservation

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. This principle is crucial for calculating the mass of reactants and products. In this problem, the initial mass of copper and the mass of sulfur used can be related to the mass of the copper sulfide produced, allowing for the determination of the empirical formula based on the mass changes during the reaction.

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Law of Conservation of Mass

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Textbook Question

A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO₂ gas. The mass of the copper sulfide produced was 2.748 g. (a) What is the percent composition of copper sulfide?

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A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO2 gas. The mass of the copper sulfide produced was 2.748 g. (b) What is its empirical formula?

Verified video answer for a similar problem:

Key Concepts

Empirical Formula

Stoichiometry

Mass Conservation

A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO₂ gas. The mass of the copper sulfide produced was 2.748 g. (b) What is its empirical formula?