Question

The molar mass of $AlC{l_3}$ ​ is:
(A) $67.9$g/mol
(B) $106.5$g/mol
(C) $62.5$g/mol
(D) $133.5$g/mol

Answer 1

Hint-Molar mass of any given compound is the sum of the atomic weight of the total elements from which the compound is composed of. The number of elements that a molecule has is also considered and the atomic weight of each and every element is added for getting the molar mass of that compound.

Complete step by step solution:
To get the molar mass of the given compound $AlC{l_3}$,firstly we should know the atomic weight of aluminium and chlorine.
So, the atomic weight of the aluminium $Al$=$27$
And atomic weight of the chlorine $Cl$=$35.5$
And the number of atoms of chlorine in $AlC{l_3}$=$3$
So the molar mass of the $AlC{l_3}$= atomic weight of the aluminium + (atomic weight of chlorine$\times$ $3$)
$AlC{l_3} = 27 + \left( {35.5 \times 3} \right)$
$AlC{l_3} = 27 + 106.5$
$AlC{l_3} = 133.5$g/mol
So, the molar mass of the $AlC{l_3}$is $133.5$g/mol.
Hence option (D) is the correct answer.

Note- Here we see that the unit of the molar mass is g/mol that is gram per mole. This gives us an idea about the molar mass. From this we can say that molar mass of any compound can be given as the mass of the given chemical element or the chemical compound in grams is divided by the amount of substance in mole. So, this is the other method with the help of which we can find the molar mass when we have given the mass of the compound and the amount of the substance. Many times, there is a confusion between the molecular weight and the molar mass. So, we should have a clear idea about that. So, the mass of the one molecule of a compound is molecular weight while the mass of one mole of the compound is known as the molar mass of that particular compound.