Inorganic compounds can broadly be classified into three main classes namely acids, bases and salt. This classification is based primarily on the fact that each class has own characteristics properties.
An acid is a substance which dissociates in water to give positively charged hydrogen (H+). H+ is called hydrogen ion. Acids have the sour taste and turn blue litmus paper into red, react with carbonates to give carbon dioxide and with metallic oxides to give salts and water.
The dissociation of Hydrochloric acid is given as:
HCl → H+ + Cl-
The dissociation of acetic acid in aqueous solution is represented as:
CH3COOH → H+ + CH3COO-
Some strong acids are commonly used in the laboratory. They are:
Generally acid denotes a substance which tastes sour but in chemistry, its meaning is not limited up to this concept only. Most substances that contain acid taste sour due to the presence of H+ ion. Example of some acids that we can gain through fruits and vegetables are:
|1.||Citric acid||Lemons, tomatoes|
|3.||Carbonic acid||Soda water|
|6.||Ascorbic acid||Citrus fruits|
|7.||Formic acid||Ants(produced by ant bite)|
1. They all contain hydrogen.
2. They possess sour taste.
3. Many acids are corrosive.
4. They turn blue litmus red.
5. They turn methyl orange into yellow color.
1. Dilute acids react with some metals like zinc, magnesium etc. to form the salt and release hydrogen gas. The metals replace the hydrogen of acids to form a salt.
Mg + 2HCl → MgCl2 + H2.
Hydrochloric acid Magnesium chloride
Zn + H2SO4 → ZnSO4 + H2
Zinc + Sulphuric acid → Zinc sulphate + Hydrogen
2. Dilute acids decompose bicarbonate and carbonates and liberate carbon dioxide.
NaHCO3 + HCl → NaCl + H2O + CO2
Sodium bicarbonate + Hydrochloric acid → Salt + Water + Carbondioxide
3. They neutralize alkali-forming salt and water.
NaOH + HCl → NaCl + H2O
(Alkali) (Acid) (Salt) (Water)
4. They react with metallic oxides to give salt and water.
Na2O + 2HNO3 → 2NaNO3 + H2O
Sodium Oxide + Nitric Acid → Sodium nitrate + Water
5. They dissolve in water to produce hydrogen ions (H+).
a. Tannic acid is used to tan leather.
b. Sulfuric acid is used in the manufacture of ammonium sulphate.
c. Sodium bicarbonate is used to make baking powder.
d. Hydrochloric acid, sulphuric acid, and nitric acid are used in the laboratory.
|1.||Turn blue litmus into the red.||Turn red litmus into blue.|
|2.||React with metals to give a salt and hydrogen gas.||Normally do not react with metals. Only some metals like zinc, aluminum and tin react to give hydrogen.|
|3.||Are corrosive to skin.||Are slippery to touch.|
|4.||Are sour in taste.||Are bitter in taste.|
|5.||React with bases to give salts and water.||React with acids to give salt and water.|
|6.||Aqueous solutions of acids contain replaceable hydrogen ions.||Aqueous solution of the base contains replicable hydroxyl ions.|
|7.||Give no color with phenolphthalein.||Give red color with phenolphthalein.|
An acid is a substance that gives hydrogen ions when dissolved in water. The physical properties of acid are:
The differences between acid and base are as follows:
|The acid gives hydrogen ion when dissolve in water.||Base gives hydroxyl ion when dissolve in water.|
|It turns blue litmus into a red.||It turns red litmus into blue.|
|It has a sour taste.||It has bitter taste.|
Orange and lemons have sour taste because they contain citric acid on them.
Acids should be handled with care because, generally concentrated acid are corrosive in nature and harm to our skin.
An acid – Nitric acid
A soluble base – Aluminum Hydroxide
A salt – Sodium Chloride
An Indicator – Litmus paper
Which one of the following is used to make fertilizers?
Potassium Hydroxide (KOH)
Lithium hydroxide (LiOH)
Sodium Hydroxide (NaOH)