The former definition of the mole was that a mole was 12 g of 12C contains 1 mole of 12C atoms (its molar mass is 12 g/mol). Per the amu definition, a single 12C atom weighs 12 amu (its atomic mass is 12 amu). (credit: modification of work by Mark Ott).īecause the definitions of both the mole and the atomic mass unit are based on the same reference substance, 12C, the molar mass of any substance is numerically equivalent to its atomic or formula weight in amu. From left to right (bottom row): 32.1 g sulfur, 28.1 g silicon, 207 g lead, and 118.7 g tin. From left to right (top row): 65.4 g zinc, 12.0 g carbon, 24.3 g magnesium, and 63.5 g copper. 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) (b) 3.06 × 10 3 g of the amino acid glycine, C 2 H 5 NO 2. Molecular mass ( molecular weight) is the mass of one molecule of a substance and is expressed in the unified atomic mass units (u). Determine the number of moles of compound and the number of moles of each type of atom in each of the following: (a) 25.0 g of propylene, C 3 H 6.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.Use uppercase for the first character in the element and lowercase for the second character. It will calculate the total mass along with the elemental composition and mass of each element in the compound. Enter the molecular formula of the substance. 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. This program determines the molecular mass of a substance. Ammonium chlorite appears as a white crystalline solid.Ĭomputing molar mass (molar weight)To calculate molar mass of a chemical compound enter its formula and click 'Compute'.
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