Question

What is the molar mass of nitroglycerin, ${{C}_{3}}{{H}_{5}}{{O}_{3}}{{(N{{O}_{2}})}_{3}}$?

Answer 1

Hint: Molar mass or molecular mass of any compound is the mass of the total atoms and their quantities involved in that compound. It is the weight of any atom in 1 mole that is $6.022\times {{10}^{23}}$particles of that atom. So it is measured in g/mol. It involves the sum of all the atoms with their quantities multiplied.

Complete answer:
Molecular weight of any molecule is the sum of the individual mass of the atoms present in that molecule. We have been given to find the molar weight of nitroglycerin. It has the formula of${{C}_{3}}{{H}_{5}}{{O}_{3}}{{(N{{O}_{2}})}_{3}}$. As from the formula we can see that nitroglycerin contains 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, while in the bracket a nitro group that is in a quantity of 3, which contains 1 nitrogen and 2 oxygen (3 times). The molecular weight will be the sum of all the masses of these atoms.
The molecular mass of carbon (C) is 12 g/mol, hydrogen (H) is 1 g/mol, oxygen (O) is 16 g/mol and that of nitrogen (N) is 14 g/mol. Therefore the molecular weight of${{C}_{3}}{{H}_{5}}{{O}_{3}}{{(N{{O}_{2}})}_{3}}$will be,
Molar mass = 3 (C) + 5 (H) + 3 (O) + 3 [N + 2 (O)]
Molar mass = 3 (12) + 5 (1) + 3 (16) + 3 [14 + 2 (16)] g/mol
Molar mass = 36 + 5 + 48 + 3 [14 + 32] g/mol
Molar mass = 89 + 138 g/mol
Molar mass = 227 g/mol
Hence the molar mass of nitroglycerin${{C}_{3}}{{H}_{5}}{{O}_{3}}{{(N{{O}_{2}})}_{3}}$is 227 g/mol or 227 u.

Note:
The molar mass or the mass number of any atom is the sum of the protons and the neutrons present in that atom, which are also called as nucleons. The number of protons is equal to the atomic number of that atom. The molar mass of any substance in gram is measured in gram per mole, also as ‘u’ that stands for unified mass and denotes gram per mole.