what r molar and molecular mass ?

The molecular mass and molar mass are two different terms and should not be confused as implying the same meaning. 

The molecular mass of a substance is the sum of the atomic masses of all the atoms present in a molecule of that substance. It is expressed in atomic mass unit (u). Thus, to calculate the molecular mass, the atomic masses of all the atoms present in it are added.

For example, Molecular mass of glucose C₆H₁₂O₆ is = 6 (C) + 12 (H) + 6 (O) = 180 u.

The molar mass, on the other hand is the mass of one mole (or 6.023 X 10²³) particles of that substance. The molar mass of a substance is numerically equal to the atomic mass or the molecular mass of the substance in ‘u’ and  is always measured in grams. For example, the molar mass or mass of 6.023 X 10²³ molecules of glucose is 180g. Similarly, mass of 6.023 X 10²³ atoms of sodium or molar mass of sodium is 23g, but its atomic mass is 23u.