Acids Bases and Salts Notes || Class 10 Chapter 2 Science ||
Chapter 2, Class 10
ACIDS, BASES AND SALTS
Acids
2. The chemical nature of such substances is
acidic.
3. The acids present in plant materials and
animals are called organic acids.
4. Organic acids (or naturally occurring
acids) are weak acids.
Important name of the Organic acids
1. Acetic acid contains in vinegar
3. Citric acid – Citrus fruits such as
oranges, lemons, etc.
6. Ascorbic acid (Vitamin C) in Amla, Citrus
fruits
Mineral Acids
1. The acids prepared from the minerals of the
earth are called mineral acids.
2. Mineral acids are manmade acids.
3. The three most common mineral acids are:
Hydrochloric acid (used in dye-stuffs (रंगनेवाला पदार्थ), textile, food and leather industries),
Sulphuric acid (used in fertilisers (खाद), paints, dyes, chemicals, detergents, explosives (बारूद) and car batteries) and Nitric acid (used
in fertilisers, explosives (like TNT: Tri-Nitro Toluene), dyes and plastics).
4. All the mineral acids are strong acids.
5. Only one mineral acid, carbonic acid, is a
weak acid.
Concentrated and Dilute Acids
1. A concentrated acid is one which contains
the minimum possible amount of water in it.
2. The concentration of an acid is decreased
by adding more water to it.
3. When water is added to a concentrated acid,
then a dilute acid is formed.
4. Thus, a dilute acid is one which contains
much more of water in it.
Properties of Acids
1. Acids have a sour taste
2. Acids turn blue litmus to red
3. Acid solutions (acid is dissolved in water)
conduct electricity (They are electrolytes)
4. Acids react with metals to form hydrogen
gas – When an acid reacts with a metal, then a salt and hydrogen gas are
formed. i.e.
Metal + Acid → Salt
+ Hydrogen gas
E.g.
when dilute Sulphuric acid reacts with zinc metal, then zinc sulphate and
hydrogen gas are formed:
Zn
(s) + H2SO4 (aq) →
ZnSO4
(aq) + H2 (g)
Zinc
(metal) (Sulphuric acid – Dilute) (Zinc sulphate – salt) Hydrogen
In
this reaction, zinc metal displaces hydrogen from sulphuric acid. And this
hydrogen is evolved as hydrogen gas. Most of the acids react with metals to
form salts and evolve hydrogen gas. This shows that hydrogen is common to all
acids.
5. Acids react with metal carbonates (and
metal hydrogen carbonates) to form carbon dioxide gas
Metal carbonate +
Acid → Salt + Carbon dioxide +
Water
Metal hydrogen
carbonate + Acid
→ Salt +
Carbon dioxide + Water
E.g. (i)
When dilute hydrochloric acid reacts with sodium carbonate, then sodium
chloride, carbon dioxide and water are formed:
Na2CO3
(s) + 2HCl (aq) → 2NaCl (aq) + CO2 (g) +
H2O (l)
Sodium
carbonate Hydrochloric
acid Sodium chloride Carbon dioxide Water
(ii) When
dilute hydrochloric acid reacts with sodium hydrogen carbonate, then sodium
chloride, carbon dioxide and water are formed:
NaHCO3
(s) + HCl (aq) → NaCl (aq)
+
CO2 (g) + H2O (l)
Sodium
hydrogen- Hydrochloric
acid Sodium
chloride Carbon Water
Carbonate dioxide
On passing
the carbon dioxide gas evolved through lime water,
When carbon
dioxide gas is passed through lime water, the lime water turns milky due to the
formation of a white precipitate of calcium carbonate
Ca (OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l)
Calcium
hydroxide Carbon
dioxide Calcium
carbonate Water
(Lime water)
(White ppt.)
(Makes lime water milky)
6. Acids react with bases (or alkalis) to form
salt and water
When an acid reacts with a base,
then a salt and water are formed. That is
Acid + Base → Salt + Water
Actually,
when an acid is treated with a base, the base neutralises the acid and destroys
its acidity. Since an acid and a base neutralise each other’s effect, so the
reaction between an acid and a base to form salt and water is called a
neutralisation reaction.
E.g. NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
Sodium hydroxide Hydrochloric acid Sodium chloride Water
(Base) (Acid) (Salt)
When
hydrochloric acid reacts with sodium hydroxide solution, then a neutralisation
reaction takes place to form sodium chloride and water
7. Acids react with metal oxides to form salt
and water
Acids react with
metal oxides to form salt and water
Metal oxide +
Acid → Salt +
Water
Copper (II) oxide is
a metal oxide. Dilute hydrochloric acid reacts with copper (II) oxide to form
copper (II) chloride and water
CuO (s) + 2HCl (aq) → CuCl2 (aq) +
H2O (l)
Copper (II)
oxide Hydrochloric acid Copper (II) chloride Water
(Black)
(Blue-green)
WHAT DO ALL ACIDS HAVE IN COMMON
An acid is
a substance which dissociates (अलग करना) (or ionises) on dissolving in water to
produce hydrogen ions [H+ (aq) ions]
E.g. an
aqueous solution of hydrochloric acid dissociates (or ionises) to form hydrogen
ions (along with chloride ions):
HCl
(aq) → H+ (aq) + Cl– (aq)
Hydrochloric
acid Hydrogen ions Chloride ions
Comments
Post a Comment