Moles can be calculated using which formula?

Moles can be calculated using which formula?

• A. moles = mass / molar mass
• B. moles = molar mass / mass
• C. moles = mass × molar mass
• D. moles = mass / (molar mass × 1)

Answer: (A)

Moles relate mass to the amount of substance through the equation m = nM, where m is mass, n is moles, and M is molar mass. Solving for n gives n = m / M, so mass in grams divided by molar mass in g/mol yields the amount in moles. For example, 24.0 g of a substance with a molar mass of 12.01 g/mol gives 24.0 / 12.01 ≈ 2.00 mol. The other forms don’t work because they yield the wrong units or meaning: dividing molar mass by mass gives 1/mol, multiplying mass by molar mass gives g^2/mol, etc. So the correct way to calculate moles is mass divided by molar mass.

Moles relate mass to the amount of substance through the equation m = nM, where m is mass, n is moles, and M is molar mass. Solving for n gives n = m / M, so mass in grams divided by molar mass in g/mol yields the amount in moles. For example, 24.0 g of a substance with a molar mass of 12.01 g/mol gives 24.0 / 12.01 ≈ 2.00 mol. The other forms don’t work because they yield the wrong units or meaning: dividing molar mass by mass gives 1/mol, multiplying mass by molar mass gives g^2/mol, etc. So the correct way to calculate moles is mass divided by molar mass.