شرح درس
Calculation of chemical formula
CHEMISTRY - Secondary 1
In This part we will study
Calculation of empirical formula
Example (1):
Calculate the empirical formula of an organic compound formed of carbon and hydrogen elements only, if you know that the mass percentage of carbon in this compound is 85.72% and that of hydrogen is 14.28%
Idea of solution
Assuming the mass of the compound is 100 g (to simplify the calculations) ,
so the mass percentage represents the gram mass of each element, therefore :
- Mass of carbon in the compound is 85 .72 g
- Mass of hydrogen in the compound is 14.28 g
Example (2):
Calculate the empirical formula of one of chromium compounds, knowing that the mass percentage of sodium in this compound is 17.5 % , of chromium is 39 .7 % and of oxygen is 42.8 %
Solution

Example (3):
Calculate the empirical formula of an organic compound composed of carbon, hydrogen and oxygen, by burning 2.3 g of a sample of this compound in excess of oxygen gas, 4.4 g of carbon dioxide and 2.7 g of water vapor are formed. [C = 12, H = 1, O = 16]
Idea of solution
* Calculation of the mass of each of carbon and hydrogen in the sample by knowing the masses of C02 and H2O produced from burning process respectively.
* Calculation of the mass of oxygen by subtracting the sum of the masses of H and C from the mass of the compound.

Best wishes to you
Mr.Ahmed Elbasha

كيمياء الصف الاول الثانوي لغات - الفصل الدراسي الاول
شرح كيمياء لغات اولي ثانوي - مستر احمد الباشا
كيمياء لغات - الصف الاول الثانوي - كيمياء اولي ثانوي الترم الاول - كيمستري اولي ثانوي الترم الاول