Atoms and Molecules Notes

• The molecular mass of a substance is the sum of atomic masses of elements (atomic mass of each element multiplied by the number of atoms of it present in the molecule). It is the relative mass of a molecule expressed in atomic mass units (u).

Question:

Calculate the molar masses of the following substances:

1. Ethyne, C₂H₂
2. Phosphorous molecule, P₄
3. Nitric acid, HNO₃

(Atomic masses: C = 12 u; H = 1 u; S = 32 u; P = 31 u; Cl= 355 u; N = 14 u; O = 16 u)