Question

What is the molar mass of barium chloride ${\text{BaC}}{{\text{l}}_2}$?

Answer 1

Barium chloride is a salt or an ionic compound consisting of two types of elements-Barium and Chlorine which contribute to its molar mass according to their individual molar masses and the stoichiometric number associated with them.

Complete answer:
Barium chloride is an ionic salt that exists as white solid. Barium is an alkaline earth metal chlorine is a halogen.
On decomposing one mole of Barium chloride we get one mole of barium metal and two moles of chlorine atoms or one more one mole of diatomic chlorine gas that can be represented as follows:
$BaC{l_2}(s) \to Ba(s) + 2Cl(g)$
$BaC{l_2}(s) \to Ba(s) + C{l_2}(g)$
The above reaction suggests that barium chloride contains one mole of barium atoms and two moles of chlorine atoms in one mole of the compound. Thus the stoichiometric number ($v$) for barium is one and chlorine is two.
One mole of a substance contains molecules equal to the Avogadro’s number $(6.022 \times {10^{23}})$.
The molar mass of a compound is the measure of total matter contained by one mole of that compound. Each atom present in the molecular formula of the compound contributes mass equal to its molar mass multiplied by its stoichiometric number.
We can find out the molar mass of barium chloride using the following formula:
${\text{Molar mass of BaC}}{{\text{l}}_2} = ({\text{molar mass of Ba)}} \times {v_{Ba}} + ({\text{molar mass of Cl)}} \times {v_{Cl}}$
${\text{Molar mass of BaC}}{{\text{l}}_2} = (137gmo{l^{ - 1}}{\text{)}} \times 1 + (35.5gmo{l^{ - 1}}{\text{)}} \times 2$
On solving this we get,
${\text{Molar mass of BaC}}{{\text{l}}_2} = 208gmo{l^{ - 1}}$

Note:
One must not get confused between atomic mass and molar mass. As molar mass is measured in grams and atomic mass is measured in atomic units $(amu)$. Atomic mass is measured according to a relative scale and it measures the mass of a single atom only.