Moles Calculator:
Enter the values of mass of the substance, m(g) and molecular weight, MW(g/mol) to determine the value of Moles, n.
Moles Formula:
The molecular weight (molar mass) of a substance is the sum of the atomic masses of all the atoms in a molecule of the substance, expressed in atomic mass units (amu) or grams per mole (g/mol). It is a fundamental concept in chemistry, used to calculate the amount of substance (moles) present in a given mass of material.
The molecular weight of a compound is determined by adding up the individual atomic weights of each element in the compound, accounting for the number of atoms of each element. Atomic weights are found on the periodic table and represent the average mass of an element’s isotopes weighted by their natural abundance.
Moles, n is equal to the mass of the substance, m(g) in grams divided by the molecular weight, MW(g/mol) of the substance in grams per mole.
Moles, n = m(g) / MW(g/mol)
n = moles.
m(g) = mass in grams, g.
MW(g/mol) = molecular weight in grams per mole, g/mol.
Moles Calculation:
1.A sample of water (H₂O) weighs 18 grams. The molecular weight of water is 18 g/mol. Calculate the number of moles in the sample.
Given: m(g) = 18g, MW(g/mol) = 18 g/mol.
Moles, n = m(g) / MW(g/mol)
n = 18 / 18
n = 1.
2.You have 0.5 moles of sodium chloride (NaCl), which has a molecular weight of 58.5 g/mol. Calculate the mass of the sample.
Given: n = 0.5mol, MW(g/mol) = 58.5 g/mol.
Moles, n = m(g) / MW(g/mol)
m(g) = n * MW(g/mol)
m(g) = 0.5 * 58.5
m(g) = 29.25g.