Final answer:
2.68 moles of sodium sulfide are equivalent to 209.1472 grams when multiplied by the molar mass of sodium sulfide, which is 78.04 g/mol.
Step-by-step explanation:
To calculate the mass in grams that is equal to 2.68 moles of sodium sulfide, Na2S, we must use the compound's molar mass. According to the information provided, the molar mass of sodium sulfide is 78.04 g/mol. Our calculation will involve multiplying the number of moles by the molar mass:
2.68 moles × 78.04 g/mol = 209.1472 grams
Hence, 2.68 moles of sodium sulfide are equal to 209.1472 grams. This is the mass of sodium sulfide corresponding to the given moles, calculated to three significant figures.