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Salts and its formation methods
CHEMISTRY - Secondary 1
In This part we will study
Salts formation methods
Salts can be practically prepared by one of the following methods:
 Reaction of active metals with diluted acids.
 Reaction of metal oxides with acids.
 Reaction of metal hydroxides with acids.
 Reaction of metal carbonates or bicarbonates with some acids.

Active metal + Acid □(→┴"dil" ) Salt of acid + Hydrogen gas ↑
 The metals above hydrogen in the chemical activity series replace hydrogen in the diluted acid solutions, giving salt of acid and hydrogen gas is evolved which burns with a pop sound.

 The salt of acid which is produced dissolves in water and can be separated by heating the solution, where the water evaporates and the salt remains.




Metal Oxide + Acid □(→┴"dil" ) Salt of acid + Water
 This method is used if there is a difficulty in the direct reaction of metal with acid because :
- The reaction is dangerous (e.g. reaction of sodium with hydrochloric acid is vigorous) .
- The metal doesn't react with the acid, because it is less reactive than hydrogen (e.g. copper doesn't react with hydrochloric acid).

Example :
Reaction of copper oxide with diluted sulphuric acid.
CuO(s) + H2SO4(aq) □(→┴"dil" ) CuSO4(aq) + H2O(l)

Metal Oxide + Acid → Salt of acid + Water
 This method is suitable in the case of metal hydroxides that are dissolving in water and considered as alkalis.
 These types of reactions are known as "Neutralization reactions" .
Neutralization reaction can be used in analytical chemistry to calculate the concentration of an acid (or an alkali) using a known concentration of a base (or an acid) in the presence of a suitable indicator.


Example :
Neutralization of sodium hydroxide with diluted hydrochloric acid.
NaOH(aq) + HCl(aq) → " " NaCl(aq) + H2O(l)

Metal Carbonate (or Bicarbonate) + Acid □(→┴"dil" ) Salt of acid + Carbon dioxide Gas ↑
 Metal carbonates or bicarbonates are salts of carbonic acid which is an unstable acid, due to its low boiling point.
 It is possible for any other acid (that is more stable than it) to replace it in its salt solutions to form a new acid salt.
 Carbonic acid decomposes into water and carbon dioxide gas, which turns the clear limewater into milky.

Example :
Reaction of sodium carbonate with diluted hydrochloric acid.
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
Note
The reaction of metal carbonates or bicarbonates with some acids is called "Acidity test"
Because this reaction is used to detect the presence of acids, as a strong effervescence occurs and CO2 gas evolves, which turns the clear limewater into turbid.

Types of aqueous solutions of salts
Applications
(1) The aqueous solution of sodium chloride is neutral.
Because NaCl is produced from the reaction between a strong acid (HCl) and a strong base (NaOH). So, the pH value is 7

(2) The aqueous solution of sodium carbonate is basic.
Because Na2CO3 is produced from the reaction between a strong base (NaOH) and a weak acid (H2CO3). So, its pH value 7

(3) The pH value of an aqueous solution of ammonium chloride is less than 7
Because this solution is acidic, where NH4Cl is produced from the reaction between a strong acid (HCI) and a weak base (NH4OH).

(4) The pH value of an aqueous solution of ammonium acetate equals 7
Because this solution is neutral, where CH3COONH4 is produced from the reaction between a weak acid (CH3COOH) and a weak base (NH4OH).

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