To determine if the scientist's expectations are correct, we need to calculate the theoretical yield of copper sulfide based on the given amounts of copper and sulfur.
First, we need to find the molar mass of copper (Cu) and sulfur (S). The molar mass of Cu is 63.55 g/mol, and the molar mass of S is 32.06 g/mol.
Next, we calculate the number of moles of Cu and S in the given amounts:
Number of moles of Cu = mass of Cu / molar mass of Cu = 12.7 g / 63.55 g/mol = 0.2 mol
Number of moles of S = mass of S / molar mass of S = 3.2 g / 32.06 g/mol = 0.1 mol
According to the balanced equation, the molar ratio of Cu to Cu2S is 1:1. Therefore, the number of moles of Cu2S formed will be equal to the number of moles of Cu reacted.
Number of moles of Cu2S formed = 0.2 mol
Finally, we calculate the mass of Cu2S formed using the molar mass of Cu2S:
Mass of Cu2S formed = number of moles of Cu2S formed x molar mass of Cu2S
= 0.2 mol x (2 x (63.55 g/mol) + 32.06 g/mol)
= 0.2 mol x 159.16 g/mol
= 31.832 g
Based on the calculations, the theoretical yield of copper sulfide (Cu2S) is 31.832 grams. This is greater than the expected yield of 15.9 grams, so it is likely that the scientist's expectations were incorrect.
Copper (Cu) reacts with sulfer (S) to form copper sulfide as shown in the equation. A scientist adds 12.7 grams of Cu to 3.2 grams of S to start the reaction. In this reaction, all of the copper and all of the sulfur react. Before running the experiment, the scientist expected the products of the reaction will be a total of 15.9 grams of copper sulfide (Cu2S).
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