Calculate the relative molecular weights, molar masses and mass fraction

| February 11, 2021 | education

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.

Мr is the relative molecular weight, equal to the sum of all the masses of the atoms included in the molecule.
М – mass of 1 mole, numerically equal to Мr
w – mass fraction of the element, calculated by the formula w = Ar * n / Mr * 100%
1) water – Мr (Н2О) = 1 * 2 + 16 = 18, М (Н2О) = 18g / mol, w (Н) = 1 * 2/18 * 100% = 11%, w (О) = 100 – 11 = 89%. w
2) carbon dioxide – Мr (СО2) = 12 + 16 * 2 = 44, М (СО2) = 44 g / mol, w (С) = 12 * / 44 * 100% = 27%, w (О) = 100 -27 = 73%.
3) table salt – Mr (NaCl) = 23 + 35.5 = 58.5, M (NaCl) = 58.5 g / mol, (Na) = 23 * 1 / 58b5 * 100% = 39%,
w (Cl) = 100-36 = 61%
4) sulfuric acid – Мr (H2SO4) = 2 + 32 + 64 = 98, М (H2SO4) = 98 g / mol, w (Н) = 2/98 * 100% = 2%, w (S) = 32 / 98 * 100% = 33%,
w (О) = 100-35 = 65% /
5) limestone – Мr (CaCO3) = 40 + 12 + 48 = 100, M (CaCO3) = 100g / mol, w (Ca) = 40/100 * 100% = 40%,
w (C) = 12/100 * 100% = 12%, w (O) = 100-52 = 48%.



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