Chemistry
Elements and Compounds
Molecular Mass

# How do you find the molecular formula of a compound?

It's very easy. First of all we test the given sample in laboratory to know about its constitution. Let's discuss it by taking an example:-

Suppose the constitution of a compound is given as below:-

C = 92.4%, H = 7.6%

let's assume that the sample is 100 gram. so the weight of carbon is 92.4 gram & that of hydrogen is 7.6 gram. Now it's we must make sure that is the total of weights of constituents 100 or not? If it is not 100, it means there is an another element in the compound, and this is always oxygen in case of hydrocarbons.

Step 1st :- Find out the number of moles of each element

number of moles = weight of the element/atomic mass

number of moles of C = 92.4/12 = 7.7 moles

number of moles of H = 7.6/1 = 7.6 mole

Step 2nd:- Find out the relative ratio of the moles:- It is simply done by dividing all by the smallest one

C = 7.7/7.6 = 1.01

H = 7.6/7.6 = 1

Step 3rd:- If the ratio is not whole numbers the multiply all the numbers by a smallest integer number to make them whole numbers.

Here in this case both are nearly whole numbers. so there is need to multiply these numbers.

C = 1

H = 1

Step 4th:- Write the empirical formula

C1H1

step 5th:- Find the weight of empirical formula

1*12 + 1*1 = 13

now if the molecular weight is given then the molecular formula can be written easily.

molecular weight = ( empirical formula weight)n

for example the molecular weight is 78.

n = 78/13 = 6

so the molecular formula is = C6H6

🙏
0
🤨
0
😮
0
😂
0

## Related Questions

If you know the molar mass of the compound, you have to calculate the mass of the empirical formula and divide the molar mass of the compound by the mass of the empirical formula in order to find the ratio between the molecular formula and the empirical formula. Then multiply all the atoms by this ratio to find the molecular formula!

This is possible only after a chemical analysis of this compound.

The formula of NO2 has a molecular weight of 46 g/mol. Your compound has a molecular weight of 92 g/mol. As you can see the molecular weight of the compound is twice that of the empirical formula. Therefore the molecular formula of your compound is:2 *(NO2) ---> N2O4

The molecular formula is established only after an accurate chemical analysis of the compound.

The molecular formula mass of this compound is 60.0 amu. The subscripts in the actual molecular formula are 2,4,2.

The molecular formula mass of this compound is 240 amu. The subscripts in the actual molecular formula 8,16,8.

This is impossible. In order to find this you must know the elements in the compound

No; the compound with the formula NH4Br is an ionic compound.

The name and the formula of a molecular compound describe the type and the number of atoms in a molecule of the compound.

Niacin is a molecular compound with the formula C6H5NO2.

A molecular formula contain indication about the chemical composition of the compound but no information about the structure.

CH2O is the molecular formula. The name of this compound is formaldehyde.

This is the chemical formula (empirical formula) or the formula unit of this compound.

Yes, the empirical formula is the most basic ratio of the elements in a compound, while the molecular formula is the ratio in a compound. For instance C5H10O could be both the empirical and the molecular formula or the molecular formula could be C10H20O2 the molecular formula depends on the molar mass.

The empirical formula for a compound whose molecular formula is P4O10 is P2O5 = phosphor pentoxide.

The molecular formula is the same as the empirical formula, NO2. The compound NO2 has a molar mass of 46g/mol, so the empirical and molecular formulas are the same.

Yes, nitrogen monoxide is a molecular compound with a formula of NO.

Phophorus pentoxide, a molecular compound with a molecular formula of P4O10 .

No: The molecular formula is never smaller than the empirical formula.

Ozone is a molecular covalently bonded compound. The molecular formula is O3

To find the molecular weight (also called the molecular mass or molar mass) of a compound or chemical, you need two things: the molecular formula of the compound and a periodic table. The molecular formula tells you how many atoms of each element is present in the compound. To find the molecular weight, just add up the atomic weights of each element present in the compound, being sure to multiply by the number of times that atom appears. The atomic weight of each element is found on a periodic table.

An empirical formula may or may not be the same as a molecular formula. The empirical formula of a compound shows the smallest whole-number ratio of the atoms compound. The molecular formula tells the actual number of each kind of atom present in a molecule of the compound.