Question

How would you find the molecular formula for a compound with the empirical formula $C{{H}_{2}}O$ and the molar mass is 180.2 g/mol?

Answer 1

In order to solve this question, we will first find out the empirical mass of the compound by adding the individual asses of the atoms present in the compound. Then we will find the value of the integral factor and on the basis of that we can write the molecular formula for the given compound.

Complete step by step answer:
- As we know that the empirical formula of the compound is $C{{H}_{2}}O$, it is found that $C{{H}_{2}}O$ has two number of hydrogen atoms, and one atom of oxygen for each carbon.
- Let us first find out the empirical mass:
Mass of the carbon atom is = 12 g
Mass of the hydrogen atom is = 1 g
Mass of the oxygen atom is = 16 g
Hence, the total mass is equal to 12 + 1+ 16 = 30 g.
- Now, as we know that the approximate molecular weight of the compound is equal to 180 g.
- As we know that the value of integral factor denoted by n is calculated by the formula:
Integral factor(n) X empirical mass = molecular mass
- So, putting the values in the above equation we get:
n X 30 = 180
n = 6
- So, we can say that the molecular formula is of $E{{F}_{n}}$ type.
$\therefore {{\left( C{{H}_{2}}O \right)}_{6}}={{C}_{6}}{{H}_{12}}{{O}_{6}}$

Note: - We should not get confused in the terms empirical formula and molecular formula. Empirical formula is the one that basically shows the simplest whole number ratio of atoms in a compound. Whereas, molecular formula is the one that shows the number of each type of atom in a molecule.
- There is also another category of formula called structural formulas that shows how the atoms are bonded to each other in a molecule.