In an experiment, 2.54 grams of copper completely reacts with sulfur, producing 3.18 grams of copper(I) sulfide,
The correct answer and explanation is:
To determine how much sulfur reacted with the copper, we can apply the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. The total mass of the reactants must equal the total mass of the products.
Step 1: Write the balanced chemical equation.
The reaction between copper and sulfur to form copper(I) sulfide is: 2Cu+S2→2Cu2S2Cu + S_2 \rightarrow 2Cu_2S
This equation shows that 2 moles of copper react with 1 mole of sulfur to produce 2 moles of copper(I) sulfide.
Step 2: Identify known quantities.
- Mass of copper (Cu) = 2.54 grams
- Mass of copper(I) sulfide (Cu₂S) = 3.18 grams
Step 3: Find the mass of sulfur used.
The mass of sulfur can be calculated by subtracting the mass of copper from the mass of copper(I) sulfide. This is based on the fact that copper and sulfur combine to form copper(I) sulfide. Mass of sulfur=Mass of copper(I) sulfide−Mass of copper\text{Mass of sulfur} = \text{Mass of copper(I) sulfide} – \text{Mass of copper} Mass of sulfur=3.18 grams−2.54 grams=0.64 grams\text{Mass of sulfur} = 3.18 \, \text{grams} – 2.54 \, \text{grams} = 0.64 \, \text{grams}
Thus, 0.64 grams of sulfur reacted with 2.54 grams of copper.
Step 4: Verify using molar masses.
For completeness, let’s check if the reaction obeys stoichiometry. The molar masses are:
- Molar mass of copper (Cu) = 63.55 g/mol
- Molar mass of sulfur (S) = 32.07 g/mol
- Molar mass of copper(I) sulfide (Cu₂S) = 159.15 g/mol
Using the mole ratios from the balanced equation and the molar masses, you could convert the masses to moles and check the proportion, but based on the mass difference, the sulfur used in the reaction is 0.64 grams.