Question

What is the molecular formula of Calcium hydride?
(A)- $Ca{{H}_{2}}$
(B)- CaH
(C)- $C{{a}_{2}}H$
(D)- $C{{a}_{2}}{{H}_{2}}$

Answer 1

Hint: Molecular formula is a chemical formula that tells us the number of atoms of each element present in the molecule.

Complete answer:
-We start by writing the element symbol of the elements present in the name of the given compound.
In this question, we have two elements, Calcium whose symbol is Ca, and the hydride which is hydrogen
anion.
-Now we will write the charge of the metal and non-metal present in the molecule.
$C{{a}^{2+}}$ and ${{H}^{-}}$

-The net charge of the molecule has to be neutral, i.e the positive and negative charges must cancel each other making the molecule electrically neutral. So balancing the charges will be the next step of this procedure. We can balance the charge by transposing only the number of the positive charge to become the subscript of the anion and the number of the negative charge to become the subscript of the cation.
$Ca{{H}_{2}}$
-The last step is converting the formula to the lowest ratio.
Here the formula is already reduced to the lowest ratio.

Therefore the molecular formula of calcium hydride is $Ca{{H}_{2}}$, i.e option A.

Note:
There are three main types of chemical formulas used in chemistry- Empirical formula, Molecular formula, and the Structural formula. You should not get confused between molecular formulas and empirical formulas. The empirical formula gives the simplest whole-number ratio of the atoms in a compound while the molecular formulas show the number of each type of atom in a molecule. The bonding and connectivity of atoms in molecules are shown by the molecular formula. Sometimes the empirical formula may be the same as the molecular formula.