What is the molar mass of Mn₂Se₇? A.) 601.34 g/mol B.) 542.50 g/mol C.) 662.60 g/mol
The Correct Answer and Explanation is:
To find the molar mass of Mn₂Se₇, we need to add the molar masses of all the atoms in the formula.
Step 1: Count the number of atoms of each element in the formula
- Manganese (Mn): 2 atoms
- Selenium (Se): 7 atoms
Step 2: Find the molar mass of each element from the periodic table
- Manganese (Mn): approximately 54.94 g/mol
- Selenium (Se): approximately 78.96 g/mol
Step 3: Multiply the atomic masses by the number of atoms
- Mn: 2 × 54.94 = 109.88 g/mol
- Se: 7 × 78.96 = 552.72 g/mol
Step 4: Add the total masses together
- Total molar mass = 109.88 + 552.72 = 662.60 g/mol
Final Answer:
C.) 662.60 g/mol
Explanation
The molar mass of a compound is the mass of one mole of that substance, measured in grams per mole (g/mol). To find the molar mass of Mn₂Se₇, we begin by identifying the number of each type of atom in the formula. The subscript next to each element symbol tells us how many atoms of that element are present. In this case, there are two manganese (Mn) atoms and seven selenium (Se) atoms in one formula unit.
The next step is to use the periodic table to find the atomic masses. Manganese has an atomic mass of about 54.94 g/mol, while selenium has an atomic mass of about 78.96 g/mol. We multiply each atomic mass by the number of atoms in the compound. For manganese, two atoms give us 109.88 g/mol. For selenium, seven atoms give us 552.72 g/mol.
After calculating the individual masses contributed by manganese and selenium, we add them together to find the total molar mass of the compound. The sum of 109.88 and 552.72 equals 662.60 g/mol. This value represents the molar mass of one mole of Mn₂Se₇.
Understanding molar mass is crucial in chemistry because it allows scientists to convert between grams and moles when performing chemical calculations. It is used in stoichiometry, chemical reactions, and determining formulas of unknown compounds. The molar mass is specific to each compound and is always calculated based on the atomic masses of the elements involved.
