شرح درس
Chemical Equation
CHEMISTRY - Secondary 1
In This part we will study
Example (1) :
Write balanced symbolic equation which represents the reaction of nitrogen gas with hydrogen gas to form ammonia gas, with writing the physical states of the reactants and the products.
Idea of Solution : (1) Writing the initial (primary) equation, and checking if it is balanced.

(2) Balancing the atoms of nitrogen by multiplying the coefficient of NH3 × 2
N2(g) + H2(g) → 2NH3(g)
The equation still unbalanced , as the number of H atoms is not equal in the reactants and in products.
(3) Balancing the atoms of hydrogen by multiplying the coefficient of H2 × 3
N2(g) + 3H2(g) → 2NH3(g)



Equation now balanced as the numbers of atoms of N and H are equal in both reactants and products.
Solution N2(g) + 3H2(g) → 2NH3(g)

Example (2) :
Write the balanced symbolic equation which represents the reaction of sodium carbonate salt with hydrochloric acid to form sodium chloride solution, water and carbon dioxide gas, with writing the physical states of each of the reactants and the products.
Idea of Solution :
(1) Writing the initial (primary) equation and checking if it is balanced.
Na2CO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)



The equation is unbalanced.
(2) Balancing sodium atoms by multiplying NaCl coefficient × 2
Na2CO3(s) + HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)


The equation is unbalanced.
(3) Balancing hydrogen atoms by multiplying HCl coefficient × 2
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)

The equation is balanced.

Solution Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
The organic compounds which are composed of:
The two elements (C and H) are known as hydrocarbons,
such as : Methane CH4 & Propylene C3H6
Or
The elements (C , H, O)
such as: Methanol CH3OH & Acetic acid CH3COOH

On complete burning with oxygen, they give carbon dioxide gas and water vapour
(or liquid water) according to the reaction conditions.

Application :
The equation of burning of glucose C6H12O6
C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(v)
Example (1) :
Write the balanced symbolic equation which represents burning of acetaldehyde liquid CH3CHO
Idea of Solution
(1) Writing the initial symbolic equation with checking if it is balanced.
CH3CHO(l) + O2(g) → CO2(g) + H2O(v)

The equation is unbalanced.

(2) Balancing carbon atoms by multiplying CO2 coefficient × 2 and balancing hydrogen atoms by multiplying H2O coefficient × 2
CH3CHO(l) + O2(g) → 2CO2(g) + 2H2O(v)

The equation is unbalanced.

(3) - Number of oxygen atoms in the products is 6 and in acetaldehyde is 1
- Balancing oxygen atoms is by multiplying O2 coefficient × 5/2
CH3CHO(l) + 5/2 O2(g) → 2CO2(g) + 2H2O(v)

The equation is balanced.
But the fraction coefficient of oxygen(5/2) must be simplified by multiplying all the coefficients × 2
This is the final balanced equation of burning of acetaldehyde liquid.
2CH3CHO(l) + 5O2(g) → 4CO2(g) + 4H2O(v)


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