Molecular formula example (Edexcel GCSE Chemistry Combined Science): Revision Notes

Molecular formula example

	Number of C atoms	Number of H atoms	RFM (Relative Formula Mass)	Conversion
Empirical formula $(CH3_33)$​	1	3	15	$2\times 2$
Molecular formula$(C2_22​H6_66​)$	2	6	30

Step-by-Step Explanation

1. Empirical Formula: $CH3_33$

The Relative Formula Mass ($RFM$) of $CH3$ is calculated as:

2. Find the Molecular Formula:

$$RFM=(12×1)+(1×3)=12+3=15$$

If the given RFM of the compound is 30, we need to find how many times the empirical formula fits into this value.

Conversion:

$$\frac{30}{15} = 2$$

3. Calculate the Molecular Formula:

Final Answer:

The molecular formula is $C2_22H6_66.$