Question

Gram molecular mass is:
a.) The mass of molecules expressed in grams.
b.) Same as the molecular mass where unified mass (u) is replaced by grams.
c.) The molar mass of the molecule in grams.
d.) Sum of the atomic mass of all the atoms of that molecule.

Answer 1

Hint: Gram molecular mass is the same as the molar mass of the substance or compound but the basic difference is that gram molecular mass specifies the mass unit which is to be used.

Complete step by step answer:
Gram molecular mass is the mass of one mole of the molecular substance expressed in grams. It is the same as molar mass; the only difference is that gram molecular mass is expressed in grams or grams per mole.
Steps to use the molecular formula to calculate gram molecular mass:

Step 1- write down the atomic mass of each of the elements present in the given formula.
Step 2- After writing down the atomic mass write down the subscript after each element symbol and multiply it with the atomic mass of that element. The subscript after each element tells us about the number of atoms of that element present in the molecule. If there is no subscript, it means that there is only 1 atom of that element in the molecule.
Step 3- Add all the values together to calculate the gram molecular mass.
Let’s take an example-find the gram molecular weight of ${{H}_{2}}S{{O}_{4}}$ is
Atomic mass of H=1 amu
Atomic mass of S= 32 amu
Atomic mass of O= 16 amu
\[(1 X 2)+(32 X 1)+(16 X 4)g = 98g\]
Gram molecular weight of ${{H}_{2}}S{{O}_{4}}$ is = 98g
So, the correct answer is “Option C”.

Note: Gram molecular mass is used in the calculation of gram moles. The relation between gram molecular mass and the number of moles of a substance is given below
\[\text{gram moles=}\dfrac{mass (grams)}{\text{gram molecular mass}}\]