Chemical Reactions and Equations Blog 2

Dear Learners,

I hope you all have started following the instruction given in previous blog. I also presume that you all have learned the symbols, valency and polyatomic ions as asked for in the previous blog.

I feel you all have not only taken the notes but also completed the home assignment in your respective chemistry note book.

In the previous blog, we have discussed about the various changes taking place in a chemical reactions with the help of equation. I must help you to recall

(i) Evolution of gas is marked by arrow key facing upward.

(ii) Formation of precipitate is marked by arrow key facing downward.

Now let us discuss the ways to write and balance a chemical equation.

Happy Learning!

At the end of this topic, learners will be able to 

(i) write a chemical formulae.

Key Instructions:

Green lines are meant to be written in note book.

Home Assignment need to be done in note book.

So, Let us begin

Formulae of Chemical Compounds: While writing the chemical formulae for compounds, we write the constituent elements and their valencies. Then we must crossover the valencies of the combining atoms. The simplest compounds, which are made up of two different elements are called binary compounds. Valency can be defined as combining capacity of an element. It can also be said as number of electrons that can be gained, lost or shared is called its valency.

Let us take few examples

1. Formula of Hydrogen chloride

              Symbol             H                  Cl              (valency cross over)

              Valency             1                  1              (same valency cancelled)

   Formula of compound would be HCl

2. Formula of Hydrogen sulphide

            Symbol                H                  S             (valency criss-cross over)

            Valency                1                  2

Formula of compound would be H₂S

3. Formula of Magnesium oxide

            Symbol           Mg                O                (valency criss-cross over)

            Valency           2                  2                 (same valency cancelled)

Formula of compound would be MgO

4. Formula of Magnesium chloride

           Symbol            Mg                 Cl           (valency criss-cross over)

           Valency            2                   1

Formula of compound  MgCl₂

5.  Formula of Aluminium oxide

           Symbol            Al                 O             (valency criss-cross over)

           Valency            3                  2

 

Formula of compound Al₂O₃

6. Formula of Calcium hydroxide

           Symbol           Ca                 OH             (valency criss-cross over)

           Valency           2                    1

Formula of compound Ca(OH)₂

7. Formula of Ammonium sulphate

           Symbol          NH₄                SO₄                 (valency criss-cross over)

           Valency          1                    2

Formula of compound    (NH₄)₂SO₄   

https://www.youtube.com/watch?v=5LOd_zkW3fE

Now, let us do the following worksheet in your note book.

Sodium Chloride	Magnesium Sulphate	Lead nitrate	Potassium iodide
Lead iodide	Potassium Nitrate	Sodium Hydroxide	Magnesium oxide
Hydrogen oxide	Copper Sulphate	Barium Chloride	Barium Sulphate
Sodium Sulphate	Silver Nitrate	Hydrogen Sulphide	Calcium Hydroxide
Aluminium Chloride	Ammonium Chloride	Sodium bicarbonate	Iron Chloride
Calcium Phosphate	Sodium Nitrate	Copper Hydroxide	Hydrogen sulphate
Lead Sulphate	Sodium Carbonate	Lead Sulphate	Calcium bicarbonate
Potassium oxide	Hydrogen Nitrate	Silver Bromide	Potassium iodide

I feel that all learners are confident to write the chemical formulae at ease.

Learner, we will meet you tomorrow positively there we will be discussing about writing equation and balancing.

Home Assignments

1. Complete the worksheet.

2. Complete your notebook.