Question

Calculate the molecular mass of chloroform $\left( {CHC{l_3}} \right)$ .
(Atomic masses : C = 12u; H = 1u; Cl = $35.5$ u).

Answer 1

The molecular mass is the mass of a given molecule. It is measured in Daltons (Da or u). To calculate the molecular mass of a given molecule, take the sum of atomic masses of all the atoms of each element in that molecule.

Complete step by step solution:
The molecular formula of chloroform is $CHC{l_3}$ . Chloroform is a compound containing one carbon atom being attached to one hydrogen atom and three chlorine atoms. The atomic mass of a carbon atom is 12 u. The atomic mass of a hydrogen atom is 1 u. The atomic mass of a chlorine atom is $35.5$ u.
The molecular mass of chloroform will be the sum of the atomic mass of one carbon atom, the atomic mass of one hydrogen atom and the atomic masses of three chlorine atoms. The atomic mass of three chlorine atoms will be three times the atomic mass of one chlorine atom.
Hence the molecular mass of chloroform can be given as follows,
Molecular mass of chloroform = atomic mass of carbon + atomic mass of hydrogen + atomic mass of three chlorine atoms
Molecular mass of chloroform = $12 + 1 + 35.5 \times 3\; = 12 + 1 + \;106.5 = 119.5$
Therefore, the molecular mass of chloroform is $119.5$ .

Note:
-Different molecules of the same compound may have different molecular masses because they might contain various isotopes of the elements.
-Total molecular mass of a compound contains 1 mole of compound.