What is the molar mass of $ MgC{l_2} $ .

Hint : Molecular mass of any molecule is calculated in term of relative molecular mass which shows that how many times a molecule of particular substance is heavier than $ {\dfrac{1}{{12}}^{th}} $ of the mass of carbon atom.
The atomic mass of hydrogen is used as standard to calculate the atomic mass of other elements but in 1961 the International Union of Chemists selected carbon isotope as standard.

Complete Step By Step Answer:
In order to calculate molar mass of the compound $ MgC{l_2} $ . We are going to calculate the atomic mass of different atoms which are combined together to form a given molecule.
 $ MgC{l_2} $ Is composed of two different types of atoms i.e. one atom magnesium $ Mg $ and two atoms of chlorine $ \left( {Cl} \right) $ .
As we know atomic mass of magnesium atom is $ \left( {Mg} \right) = 24.3 $
Atomic mass of chlorine atom is $ \left( {Cl} \right) = 35.5 $
Now for calculating the molar mass of magnesium chloride, add the atomic masses of all the atoms present in the molecule.
Molecular mass of $ \left( {MgC{l_2}} \right) $ = atomic mass of magnesium atom $ \left( {Mg} \right) $ + atomic mass of chlorine atom $ \left( {Cl} \right) \times 2 $
 $ \left( {MgC{l_2}} \right) $ = $ 24.3 + 35.5 \times 2 $
 $ \left( {MgC{l_2}} \right) $ = $ 24.3 + 71 $
After solving the above equation we get
 $ \left( {MgC{l_2}} \right) = 95.3u $
Molecular mass is designated in terms of $ \left( u \right) $ which is known as “unified mass”.

Note :
Remember to double the atomic weight of chlorine atom $ \left( {Cl} \right) $ because two atom are present in one molecule of $ \left( {MgC{l_2}} \right) $
Nowadays molecular mass of different elements are calculated accurately by using a mass spectrometer.
When the molecular mass of the compound is expressed in terms of grams it is known as gram molecular mass. For example- the molecular mass of $ \left( {Mg} \right) $ is $ 24.3 $ , therefore its gram molecular mass is $ 24.3g $ .