Hii experts pls explain according to.class 9 level ..now what is emperical formula ..pls refer the attached image and give the desired ans to the asked question ..regards

Dear student

 

Empirical formula of a compound can be defined as the formula which gives the simplest whole number ratio of atoms of the various elements present in the molecule of a compound.

The following example will help you to understand the meaning of empirical formula

I am hereby listing down the steps for writing empirical formula. Follow them in the given order.

1.  Divide the percentage of each element by its atomic mass.

2.  Divide the quotients obtained in the above step by the smallest of them to get a simple ratio of moles of various elements.

3.  Multiply the figure, so obtained by a suitable integer (if necessary) to get a whole number ratio.

4.  Finally write down the symbols of various elements side by side and put the above number as subscripts to the lower right hand side corner of each symbol.

 

For clear and better understanding, here is an example showing the calculation of empirical formula of a compound.

 

Q. Calculate the empirical formula of a compound having following percentage composition C = 40% H = 6.67% and the rest oxygen
Given :
Percentage of hydrogen in the compound = 6.67%
Percentage of carbon in the compound = 40 %
Percentage of oxygen in the compound = 100- 40 -6.67 = 53.33 %

Therefore, in 100 g of the compound 
Mass of hydrogen = 6.67 g
Mass of carbon = 40 g 
Mass of oxygen = 53.33 g .

No. of moles in 6.67g  of hydrogen = Mass of hydrogen / Molar mass of hydrogen
                        = 6.67 /1 = 6.67

No. of moles  in 40g of carbon = 40 / 12 = 3.33

No. of moles in in 53.33g of oxygen = 53.33 / 16 = 3.33

Ratio of moles of C, H and O = 3.33 : 6.67 : 3.33

Simplest ratio  = 1:2:1
Therefore, empirical formula of the compound = CH₂O

Regards