The molar mass of a compound can be found on the periodic table, usually under the name of the element. For example, the molar mass of iron (II) chloride (FeCl2) is calculated by multiplying the atomic mass of iron (56 g/mol) by the number of atoms of iron (1), and then multiplying the atomic mass of chlorine (35.5 g/mol) by the number of atoms of chlorine (2). It is calculated by multiplying the atomic mass of each element in the compound by the number of atoms of that element in the compound, and then adding the results together. Molar mass is the ratio of the mass of a molecule compared to the unified atomic mass unit. Recap: The periodic table with molar masses "Moles and Molar Mass" and "Avogadro's Number and the Mole" are both great places to start. We have articles on our site that can help you understand the basics before we get into calculating. For now, you can use the terms interchangeably. But, if we ever do chemistry on other planets or in space, we will use atomic mass. When we do chemistry on Earth, we use atomic weight. Atomic weight is what you would measure for the atomic mass near (or on the surface of) a heavy object. The units for both measures are atomic mass units.Ītomic mass is defined as the rest mass of an atom, usually expressed in atomic units. This helps you figure out the molecular mass by adding up the atomic masses. So, you use something called atomic mass to calculate how much they weigh. You face a similar problem every day - you need to know how many atoms you need, but counting them out one by one is impossible. In this case, it would be 10 kilograms of sand per batch of cement. Then you can calculate the total weight of sand you need. That means each grain is 1/10th of a milligram. Let's say you find out that each grain of sand weighs 10 milligrams. To figure out how much sand you need, you can measure the weight of an average grain of sand by weighing 100 of them on a scale. The molar mass of carbon dioxide is 12.01 + (2 × 16.00) = 44.01 g/mol.Have you ever been given a task with a really specific requirement? Like, for instance, at a construction site, where the engineer says you need to use 100 million grains of sand for every batch of cement mixed? You might think you need to sit there and count out every grain of sand, but there's a better way to do things.CO 2 has one carbon atom and two oxygen atoms.Oxygen (O) has an atomic mass of about 16.00 amu.Carbon (C) has an atomic mass of about 12.01 amu.Let's calculate the molar mass of carbon dioxide (CO 2): Add them together: add the results from step 3 to get the total molar mass of the compound.Calculate molar mass of each element: multiply the atomic mass of each element by the number of atoms of that element in the compound.The atomic mass is usually found on the periodic table and is given in atomic mass units (amu). Find atomic masses: look up the atomic masses of each element present in the compound.For example, water is H 2O, meaning it contains two hydrogen atoms and one oxygen atom. Identify the compound: write down the chemical formula of the compound.One mole contains exactly 6.022 ×10 23 particles (Avogadro's number) Mole is a standard scientific unit for measuring large quantities of very small entities such as atoms and molecules.Molar mass ( molar weight) is the mass of one mole of a substance and is expressed in g/mol.(1 u is equal to 1/12 the mass of one atom of carbon-12) Molecular mass ( molecular weight) is the mass of one molecule of a substance and is expressed in the unified atomic mass units (u).To calculate molecular weight of a chemical compound enter it's formula, specify its isotope mass number after each element in square brackets.Įxamples of molecular weight computations: Molar mass calculator also displays common compound name, Hill formula, elemental composition, mass percent composition, atomic percent compositions and allows to convert from weight to number of moles and vice versa.Ĭomputing molecular weight (molecular mass) Functional groups: D, Ph, Me, Et, Bu, AcAc, For, Tos, Bz, TMS, tBu, Bzl, Bn, DmgĮxamples of molar mass computations: NaCl, Ca(OH)2, K4, CuSO4*5H2O, nitric acid, potassium permanganate, ethanol, fructose, caffeine, water.Capitalize the first letter in chemical symbol and use lower case for the remaining letters: Ca, Fe, Mg, Mn, S, O, H, C, N, Na, K, Cl, Al. Carbon dioxide is a colorless and odorless gas at standard temperature and pressure.Ĭomputing molar mass (molar weight)To calculate molar mass of a chemical compound enter its formula and click 'Compute'.
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