Methyl orange

Phenolphthalein

A method for determining the type of solution in numerical values ranging from 0 to 14. Papers and digital devices are used to measure the pH of solutions

N.B: Read chapter (1) to know more about pH measurement

 If the pH of a solution is less than 7, so its acidic

 If the pH of a solution equals 7, its neutral

 If the pH of a solution is greater than 7, so its basic

PH indicator colour chart

How to form salts

The reaction of metals with diluted acids: Metals which come before hydrogen in chemical activity series (which we studied last year) replace it in its diluted acids solutions forming salt and hydrogen gas

Active metal + diluted acid  Salt of acid + Hydrogen

Zn(s) + H2SO4  ZnSO4 + H2 – (g)

The reaction of metal oxides with acids: This method is usually used in the case of the difficult of the reaction of metal with acid due to the danger of reaction or the decrease of metal acitivity

Metal oxide + Acid  water + salt of acid

CuO(s) + H2SO4  CuSO4 (aq) + H2O(l)

The reaction of metal hydroxide with acids: This method is valid in the case of soluble metal hydroxides, which are form Alkalis

Acid + Alkali  Salt + Water

HCl (aq) + NaOH (aq)  NaCl(aq) + H2O (l)

Neutralization reaction: The reaction of acids with alkalis forming water and salts

The importance of neutralization reactions: They are used in chemical analysis process in order to calculate the concentration of an acid or alkali using acids and alkalis with known concentrations in the presence of suitable indicators.

The reaction of metal carbonates (or bicarbonates) with acids: stable carbonate acid salts can be replaced by stable acids forming the new acid salt and carbon dioxide gas. This reaction is used to test acidity

Na2CO3 (s) + 2HCl (aq)  2NaCl(aq) + H2O(l) + CO2 (g) -

Nomenclature of salts

Anion: Negative ion

Cation: Positive ion

 A salt is formed when the negative ion (anion) of an acid (Y-) binds with the positive ion (cation) of a base (X+) forming salt (XY). Thus, the chemical name of a salt is composed of two terms (Such as sodium chloride and potassium chloride)

 The 1^st term of salt chemical name describes the negative ion of acid (Anion) while the 2^nd term describes the positive ion of base (Cation)

 The chemical formula of a salt depends on the valency of the anions and cations forming them (the following table mentions some acids, their structures, and the salts prepared by them)

Salts prepared by acid	Anion	The acid
- Potassium nitrate (KNO3) - lead nitrate Pb(NO3)2 - iron nitrate III Fe(NO3)3	Nitrates NO3 -	Nitric acid HNO3
- Sodium chloride (NaCl) - Magnesium chloride MgCl2 - Aluminium chloride AlCl3	Chloride Cl-	Hydrochloric acid HCl
- Potassium acetate CH3COOK - Copper acetate (CH3COO)2Cu - Iron acetate III (CH3COO)3 Fe	Acetate CH3COO-	Acetic acid CH3COOH
- Sodium sulphate Na2SO4 - Sodium bisulphate NaHSO4 - Copper sulphate CuSO4 - Copper bisulphate CuHSO4	Sulphate (SO4)-2 Bisulphate (HSO4)-	Sulphuric acid H2SO4
- Sodium carbonate Na2CO4 - Sodium bicarbonate Na2HCO4 - Calcium carbonate CaCO3 - Magnesium bicarbonate Mg(HCO3)2	Carbonate (CO3) Bicarbonate (HCO3)	Carbonic acid H2CO3

We notice from the previous table that:-

1- Some acids have two kinds of salts because their molecules have 2 hydrogen atoms (dibasic acids) , Dibasic acids (such as sulphuric and carbonic acids) have two kinds of salts because the molecules of each of them have 2 hydrogen atoms.

Tribasic acids (such as phosphoric acid) have three kinds of salts because their molecules contain 3 hydrogen atoms

2- The names of salts which contain hydrogen in their anions are called "bi____" "Hydrogen _____"

 HSO4- can be called "Bisulphate" or "Hydrogen sulphate"

3- Numbers II and III indicates the valency of the metal bound to the anion of the acid, (Such numbers are written in cases of multivalent metals – metal having more than one valence such as iron)