what is meant by a acid base and salt explain briefly
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Acids
An Acid is a substance that gives H+ ionswhen dissolved in water.
Acids are compounds that contain Hydrogen (Hydrochloric, HCl; Sulphuric, H2SO4; Nitric, HNO3). However, not all compounds that contain Hydrogen are acids (Water, H2O; Methane, CH4). Acids are usually compounds of non metals with Hydrogen and sometimes Oxygen.
The three acids above react with water in the following ways:
HCl ---- (H2O) ----> H+ + Cl-
H2SO4 ---- (H2O) ----> 2H+ + SO42-
HNO3 ---- (H2O) ----> H+ + NO3-
Sulphuric, Hydrochloric and Nitric acids are inorganic. There are also organicacids. Acetic acid (found in vinegar) has the formula CH3CO2H. Not all the Hydrogen atoms give H+ ions in water. In acetic acid, only the Hydrogen attached to the Oxygen yield a H+ ion.
CH3CO2H ---- (H2O) ----> H+ + CH3CO2-
Many acids only show acidic properties when water is present.
Acids are corrosive and can burn flesh and dissolve metal.
Bases and Alkalis
A Base is a substance that gives OH- ionswhen dissolved in water.
Bases are usually metal hydroxides (MOH). Examples include Sodium Hydroxide, NaOH, Calcium Hydroxide, Ca(OH)2. The solution of a base in water is called an alkali.
The two bases above react with water in the following ways:
NaOH ---- (H2O) ----> Na+ + OH-
Ca(OH)2 ---- (H2O) ----> Ca2+ + 2OH-
Alkalis have a soapy feel and can corrode.
pH
Acidity is measured on a scale called pH. The value of pH determines how acidic or basic a solution is. A pH of 1 is very acidic; a pH of 14 is a strong alkali. A neutral solution (or pure water) has a pH of 7.
There are chemicals that change colour at different pH values. These are called indicators. One of the most famous is Litmus. This substance turns red when the pH is less than 7 (acidic) and turns blue when the pH is greater than 7 (basic).
Salts
A Salt results when an acid reacts with a base. Both are neutralised. The H+ and OH- ions combine to form water. The non metalic ions of the acid and the metal ions of the base form the salt.
Acid + Base ----> Salt + Water
Examples:
HCl + NaOH ----> NaCl + H2O
H2SO4 + Ca(OH)2 ----> CaSO4 + H2O
NaCl is Sodium Chloride (common salt); CaSO4 is Calcium Sulphate.
The salt ions normally stay in solution. The salt crystalizes out when the water is removed. Some salts are insoluble. They will precipitate out when the acid and base are added together. Barium Chloride behaves like this:
2HCl + Ba(OH)2 ----> 2H2O + BaCl2
Barium Chloride (BaCl2) appears as a white precipitate.
Salts can be formed in other ways. When metals dissolve in acids, a salt is formed along with Hydrogen:
Acid + Metal ----> Salt + Hydrogen
In the example below Magnesium dissolves in Sulphuric Acid to give Magnesium Sulphate and Hydrogen which appears in the form of bubbles:
H2SO4 + Mg ----> MgSO4 + H2
Many metal carbonates are unstable. When they dissolve in acids, a salt is formed along with water and Carbon Dioxide:
Acid + Metal Carbonate ----> Salt + Water + Carbon Dioxide
In the example below Calcium Carbonate dissolves in Hydrochloric Acid:
2HCl + CaCO3 ----> CaCl2 + H2O + CO2
Calcium Carbonate has many forms (chalk, marble and limestone) which are used for building. These substances are corroded by even weak acids as in acid rain.
An Acid is a substance that gives H+ ionswhen dissolved in water.
Acids are compounds that contain Hydrogen (Hydrochloric, HCl; Sulphuric, H2SO4; Nitric, HNO3). However, not all compounds that contain Hydrogen are acids (Water, H2O; Methane, CH4). Acids are usually compounds of non metals with Hydrogen and sometimes Oxygen.
The three acids above react with water in the following ways:
HCl ---- (H2O) ----> H+ + Cl-
H2SO4 ---- (H2O) ----> 2H+ + SO42-
HNO3 ---- (H2O) ----> H+ + NO3-
Sulphuric, Hydrochloric and Nitric acids are inorganic. There are also organicacids. Acetic acid (found in vinegar) has the formula CH3CO2H. Not all the Hydrogen atoms give H+ ions in water. In acetic acid, only the Hydrogen attached to the Oxygen yield a H+ ion.
CH3CO2H ---- (H2O) ----> H+ + CH3CO2-
Many acids only show acidic properties when water is present.
Acids are corrosive and can burn flesh and dissolve metal.
Bases and Alkalis
A Base is a substance that gives OH- ionswhen dissolved in water.
Bases are usually metal hydroxides (MOH). Examples include Sodium Hydroxide, NaOH, Calcium Hydroxide, Ca(OH)2. The solution of a base in water is called an alkali.
The two bases above react with water in the following ways:
NaOH ---- (H2O) ----> Na+ + OH-
Ca(OH)2 ---- (H2O) ----> Ca2+ + 2OH-
Alkalis have a soapy feel and can corrode.
pH
Acidity is measured on a scale called pH. The value of pH determines how acidic or basic a solution is. A pH of 1 is very acidic; a pH of 14 is a strong alkali. A neutral solution (or pure water) has a pH of 7.
There are chemicals that change colour at different pH values. These are called indicators. One of the most famous is Litmus. This substance turns red when the pH is less than 7 (acidic) and turns blue when the pH is greater than 7 (basic).
Salts
A Salt results when an acid reacts with a base. Both are neutralised. The H+ and OH- ions combine to form water. The non metalic ions of the acid and the metal ions of the base form the salt.
Acid + Base ----> Salt + Water
Examples:
HCl + NaOH ----> NaCl + H2O
H2SO4 + Ca(OH)2 ----> CaSO4 + H2O
NaCl is Sodium Chloride (common salt); CaSO4 is Calcium Sulphate.
The salt ions normally stay in solution. The salt crystalizes out when the water is removed. Some salts are insoluble. They will precipitate out when the acid and base are added together. Barium Chloride behaves like this:
2HCl + Ba(OH)2 ----> 2H2O + BaCl2
Barium Chloride (BaCl2) appears as a white precipitate.
Salts can be formed in other ways. When metals dissolve in acids, a salt is formed along with Hydrogen:
Acid + Metal ----> Salt + Hydrogen
In the example below Magnesium dissolves in Sulphuric Acid to give Magnesium Sulphate and Hydrogen which appears in the form of bubbles:
H2SO4 + Mg ----> MgSO4 + H2
Many metal carbonates are unstable. When they dissolve in acids, a salt is formed along with water and Carbon Dioxide:
Acid + Metal Carbonate ----> Salt + Water + Carbon Dioxide
In the example below Calcium Carbonate dissolves in Hydrochloric Acid:
2HCl + CaCO3 ----> CaCl2 + H2O + CO2
Calcium Carbonate has many forms (chalk, marble and limestone) which are used for building. These substances are corroded by even weak acids as in acid rain.
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