# Calculate the relative molecular weights, molar masses, and mass fraction of each element

Calculate the relative molecular weights, molar masses, and mass fraction of each element in a molecule of water, carbon dioxide, sodium chloride, sulfuric acid, and limestone.

To determine the relative molecular mass of a substance Mr, it is necessary to add the relative atomic masses of the elements that make up the compound, multiplying by the indices at the elements. The molar mass is numerically equal to Mr, but shows how much a mole of a substance weighs and is measured in g / mol.

Mr (H2O) = 2 * Ar (H) + Ar (O) = 2 + 16 = 18 amu. eat.

M (H2O) = 18 g / mol.

w (H) = 2/18 * 100% = 11.1%

w (O) = 16/18 * 100% = 88.9%

Mr (CO2) = Ar (C) + 2 * Ar (O) = 12 + 2 * 16 = 44 amu. eat.

M (CO2) = 44 g / mol.

w (C) = 12/44 * 100% = 27.3%

w (O) = 16 * 2/44 * 100% = 72.7%

Mr (NaCl) = Ar (Na) + Ar (Cl) = 23 + 35.5 = 58.5 a. eat.

M (NaCl) = 58.5 g / mol.

w (Na) = 23 / 58.5 * 100% = 39.3%

w (Cl) = 35.5 / 58.5 * 100% = 60.7%

Mr (H2SO4) = 2 * Ar (H) + Ar (S) + 4 * Ar (O) = 2 + 32 + 4 * 16 = 98 amu. eat.

M (H2SO4) = 98 g / mol.

w (H) = 2/98 * 100% = 2.0%

w (S) = 32/98 * 100% = 32.7%

w (O) = 64/98 * 100% = 65.3%

Mr (CaCO3) = Ar (Ca) + Ar (C) + 3 * Ar (O) = 40 + 12 + 3 * 16 = 100 amu. eat.

M (CaCO3) = 100 g / mol.

w (Ca) = 40/100 * 100% = 40.0%

w (C) = 12/100 * 100% = 12.0%

w (O) = 48/100 * 100% = 48.0% One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.