Q3.4P - Chemistry: Molecular Nature Of Matter And Change

Question

3.4 How is the molecular mass of a compound the same as the molar mass, and how is it different?

Step-by-Step Solution

Answer

They both represent mass, so that's something they have in common. They do, however, represent different quantities.

Step 1: Determination of molecular mass

The sum of the atomic masses of all the atoms in a substance's molecule is its molecular mass. It's a term for substances with molecules as constituent particles. Therefore, the molecular mass is the average mass of the molecule.

Step 2: Determination of molar mass

Molar mass is defined as the mass of one mole of the substance. It is measured in g/mol unit.

Step 3: Similarity between molecular mass and molar mass

A molecule's mass is defined as its molecular weight. The mass of one mole of molecules is referred to as molar weight.

Both molecular mass and molar mass signify mass, therefore that's something they share.

Step 4: Difference between molecular mass and molar mass

Molecular mass and molar mass both signify distinct quantities. The unit of molar mass is g/mol, whereas molecular mass is represented in a.m.u, that is, atomic mass unit. 

Molar mass can be calculated by diving the mass of the substance by the moles of the substance, whereas molecular mass is directly used from the periodic table or calculated by the mass of the substance relative to the $\frac{\mathbf{1}}{\mathbf{12}}\mathbf{th}$ of the carbon-12 atom.