Molar mass is the mass (in grams) of one mole of a substance. Enter the molecular formula of the molecule. Count how many atoms of each element exist in the molecule. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group. In this case, it's five digits (from the atomic mass for calcium). The empirical formula mass of #"CH"_2"O"# is 30.03 u. It's easy to find the molecular mass of a compound with these steps: The total will be the molecular mass of the compound. % of people told us that this article helped them. We know ads can be annoying, but they’re what allow us to make all of wikiHow available for free. Chemists use an instrument called a mass spectrometer to determine the molar mass of compounds. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group. To work with meaningful amounts of substances, scientists group them into units called moles. What's the difference between the molar mass of a compound and the molar mass of an aqueous solution of that same compound? How to Calculate Mass in Grams of a Molecule By Chris Deziel; Updated February 26, 2018 To calculate the molecular mass of a compound, you need to know two things. To find the molar mass, find the atomic mass of all the components of a chemical. Watch rules for rounding and truncating, which depend on the situation. To see specific examples for how to calculate molar mass, read on! How can I calculate the content of Copper in Copper Gluconate? To calculate the molar mass of an element, find the relative atomic mass of that element, then multiply the relative atomic mass by the molar mass constant. One mnemonic device for remembering diatomic elements (molecules of 2 atoms) is: Have No Fear Of Ice Cold Beverages (Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine). How can I calculate the molar mass if only the atomic weight is given? Therefore, the molar mass of water, is 18. A subscript applies to the atom symbol it follows. There are three hydrogen atoms, as indicated by the subscript. In this case, hydrogen has an atomic mass of 1, and oxygen has an atomic mass of 16. This will be the smallest number of significant figures in the atomic mass values. In practice, the relative molecular mass of a compound, M r , is the sum of the relative atomic masses ( atomic weights ) of the atomic species as given in the chemical formula . ", "Gave me a clear and concise answer right before I was about to give up from stress. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. How do you calculate the molar mass of water? For example, to find the molecular mass of NH3, the first step is to look up the atomic masses of nitrogen (N) and hydrogen (H). First, list each element present in the molecule. This number is called Avogadro's number or Avogadro's constant. This constant is used as the number of atoms given by one mole for any substance, and the mass of 1 mole of a substance is its molar mass. Calculate the molar mass of the compound #"Molar mass" = "mass"/"moles" = "32.4 g"/"0.36 mol" = "90.0 g/mol"# Calculate the molecular formula of the compound. The molar mass calculation of a substance is complete the following steps (We will use sulfuric acid, H 2 SO 4, as an example): Make a list of each element and the number of atoms of each element present in the substance. The relative atomic masses of the elements in hydrochloric acid are: hydrogen, 1.007 g/mol and chlorine, 35.453 g/mol.  X Research source Using the atomic mass of an element and multiplying it by the conversion factor grams per mole (g/mol), you can calculate the molar mass of that element.