Question

Calculate the relative formula mass for calcium chloride, $CaC{l_2}$.

Answer 1

Hint- The relative formula mass of a substance composed of molecules is the total of the relative atomic masses of the atoms in the numbers appeared in the formula. Relative formula mass has the symbol, ${M_r}$.

Complete answer:
Relative formula mass has the symbol, ${M_r}$ . To figure the Mr for a substance:
Find out the number of atoms of every element there is in the chemical formula.
Add together the relative atomic mass values for all the atoms of every element present.
Now, we know that:
Atomic mass of calcium is 40 amu.
Atomic mass of chlorine is 35.5 amu.
Thus, the relative formula mass of $CaC{l_2}$ will be-
$
   \Rightarrow {M_r} = \left( {1 \times 40} \right) + \left( {2 \times 35.5} \right) \\
    \\
   \Rightarrow {M_r} = 111amu \\
$
The relative formula mass for an ionic compound is like the relative molecular mass ${M_r}$ of a covalent compound, simply because ionic compounds don't generally frame molecules (they structure huge cross sections) we can't discuss molecular units.
Relative formula mass uses a similar symbol as relative molecular mass ${M_r}$ and is equivalent to the total of the relative atomic masses of the atoms in a formula unit of the compound.
Hence, the formula unit mass of calcium chloride is 111 amu.

Note: Atoms have next to no mass so their relative atomic masses are used. The relative atomic mass of an element, symbol ${A_r}$, is the relative mass of its atoms contrasted with the mass of a carbon-12 atom.