Q79P - Chemistry: Molecular Nature Of Matter And Change

Question

How is a structural formula similar to a molecular formula? How is it different?

Step-by-Step Solution

Answer

The structural and the molecular formula of a compound are the same but the structural formula also shows the bonds between the atoms. So the structural formula provides some additional information as compared to the molecular formula.

Step 1Define the structural formula of the compound

The structural formula of the compound shows the bonds between the atoms and also depicts the number of atoms. Thus, the structural formula of a compound shows the connections of the atoms in the molecule and the relative placement of the atoms. For example, the structural formula of ethylene is ${\mathbf{H}}_{\mathbf{2}}\mathbf{C}\mathbf{=}{\mathbf{CH}}_{\mathbf{2}}$ each H is bonded to the C, and the C atoms are bonded to each other.

Step 2: Define the molecular formula of the compound

The molecular formula depicts the actual number of elements present in that particular compound. For example, in ethylene, two carbon and four hydrogen atoms are present. Therefore, the molecular formula of ethylene is ${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{4}}$. 

Step 3: similarities between the structural and molecular formula

The structural and the molecular formula of a compound gives the same but the structural formula also shows the bonds between the atoms. So, the structural formula shows how the atoms are connected in the compound. 

For example, in water two hydrogen and oxygen atoms are present. So, the molecular formula and the structural formula of water are the same, that is, ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ but the structural formula shows that each hydrogen atom is bonded to the oxygen atom. $\mathbf{H}\mathbf{-}\mathbf{O}\mathbf{-}\mathbf{H}$.

Step 4: Difference between the structural and molecular formula

The major difference between the structural and the molecular formula is that shows the arrangement of the atoms and also depicts the relative position of the functional groups. The structural formula also helps in predicting the nature of bonding, polarity, and other physical properties of the compound.