In Chemistry, the molecular formula is an essential term for a chemical compound. It helps you in identifying atoms present in the compound and fragments. However, to calculate the molecular formula, we need to know the empirical formula first. In some cases, the empirical formula and the molecular formula of the molecule or the molecular substance is the same, and in other instances, the molecular formula may have more significant numbers.

Not to forget that the molecular formula gives more information about a little substance than an empirical formula. The molecular method also determines the element of the material and defines whether it is a binary compound, ternary compound, quaternary compound or has more features.

Now that we know the use of molecular formula let’s find out how to calculate the molecular formula.

Calculating Molecular Formula:

For calculating Molecular Formula, we’ll have to understand the empirical formula first. The Empirical Formula provides the most reduced ratio of elements within a molecular substance. Also, you need to know that a whole number ratio relates the two formulas.

For example, a chemical compound’s empirical formula is C12OH30 and molecular formula is C24O2H60 with a ratio of 2.

To find out the Molecular formula first we have to Calculate the number of moles of gas. We can use the ideal gas law to determine the number of moles based on different variables like the pressure, volume, and temperature. The formula to calculate that is n = PV/RT. Here, n is the number of moles, P is the pressure, V is the volume, T is the temperature in Kelvin, and R is the gas constant.

After calculating the moles of gas, you need to Calculate the molecular weight of the gas. To do that you need to know how many grams of gas was present in the molecule. Then divide the grams of gas by the moles of gas to get the molecular weight of the gas.

In the next step, you’ve to find the weight of the empirical formula. In the empirical formula, each atom has its atomic weight. To know the atomic weight, you can refer to the periodic table. The value will be at the bottom of the atom’s square. After that, you have to add them together to get the weight of the empirical formula.

Now compare the Empirical Formula weight with the Molecular weight of the gas. By dividing the molecular weight by empirical weight, you’ll get to know the no. of times empirical formula repeats itself in the molecular formula. The result should be a whole number. If not then you will have to round it.

Lastly, multiply the elements of the empirical formula with the ratio. The result will be the molecular formula. Remember that if a compound has a ratio of “1,” then the empirical formula and molecular formula will be the same.

In this section, we have covered the chapter of molecular formula. We discussed the two different formula of a chemical compound, i.e. empirical formula and molecular formula. For a quick recap, the empirical formula is the lowest whole number ratio between the elements in a mixture (may not be the actual formula of the compound). Also, The molecular formula is the exact formula which includes the fixed ratio among the various elements in the molecule. You can take some more examples to practice this method.

I hope that you have a clear idea about molecular formula and empirical formula and the relation between them. We’ve also discussed the method to find the molecular formula of a chemical compound. For more queries leave a comment in the comment section below.