Question

Define the terms : 

a) molecular mass, 

b) formula unit mass, 

c) mole and 

d) molar mass.

Answer 1

a) Molecular mass : 

The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of a substance. 

b) Formula unit mass : 

The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of a compound.

c) Mole : 

1) One mole of a substance is the amount of the substance which contains as many particles or entities that are equal to the atoms present in exactly 12 grams of C¹² isotope. 

2) The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

d) Molar mass : 

The mass of 1 mole of a substance which is expressed in grams is called its molar mass.