Question

What is the difference between formula unit mass and molecular mass and please explain mole concept .

Answer 1

Formula Unit Mass :-

• The formula mass (formula weight) of a molecule is the sum of the atomic weights of the atoms in its empirical formula.
• The empirical formula is also known as the simplest formula. It is used to indicate the mole ratio of elements present in a compound. The empirical formula of glucose would be CH₂O.

Molecular Mass :-

• The molecular mass (molecular weight) of a molecule is its average mass as calculated by adding together the atomic weights of the atoms in the molecular formula.
• The molecular formula indicates the type and number of atoms in a molecule. The molecular formula of glucose is C₆H₁₂O₆, which indicates that one molecule of glucosecontains 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen.

The MOLE CONCEPT

• The identity of a substance is defined not only by the types of atoms or ions it contains, but by the quantity of each type of atom or ion. For example, water, H₂O, and hydrogen peroxide, H₂O₂, are alike in that their respective molecules are composed of hydrogen and oxygen atoms.
• A mole is defined as the amount of substance containing the same number of discrete entities (such as atoms, molecules, and ions) as the number of atoms in a sample of pure ¹²C weighing exactly 12 g.
• The number of entities composing a mole has been experimentally determined to be 6.02214179 × 10²³, a fundamental constant named Avogadro’s number (N_A) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro. This constant is properly reported with an explicit unit of “per mole,” a conveniently rounded version being 6.022 × 10²³/mol.
• Consistent with its definition as an amount unit, 1 mole of any element contains the same number of atoms as 1 mole of any other element. The masses of 1 mole of different elements, however, are different, since the masses of the individual atoms are drastically different.