Notes For ICSE Class 10 Chemistry Study of Compounds Hydrogen Chloride

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Study of Compounds Hydrogen Chloride ICSE Class 10 Chemistry Revision Notes

Students can refer to the quick revision notes prepared for Chapter Study of Compounds Hydrogen Chloride in Class 10 ICSE. These notes will be really helpful for the students giving the Chemistry exam in ICSE Class 10. Our teachers have prepared these concept notes based on the latest ICSE syllabus and ICSE books issued for the current academic year.

Revision Notes ICSE Class 10 Chemistry Study of Compounds Hydrogen Chloride

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Hydrogen Chloride

Molecular formula: HCl
Molecular mass: 36.5 amu
Bond: Covalent

General Preparation of HCl gas
i. By synthesis
Moist hydrogen gas combines with chlorine in the presence of diffused sunlight

Laboratory Preparation of Hydrogen Chloride
Hydrogen chloride gas is prepared by heating a metallic chloride (NaCl) with conc. sulphuric acid (H2SO4).
Reactions:

Collection
• Hydrogen chloride gas is collected by the upward displacement of air as it is 1.28 times heavier than
air.
• It is not collected over water because it is highly soluble in water.

Physical Properties
• Colourless, pungent, choking odour, slight sour taste.
• It is 1.28 times heavier than water and highly soluble in water.
• Liquefies at temperature of about 10°C at 40 atmospheric pressure.
• Boiling point is −83°C, and freezing point is −113°C.

Chemical Properties of HCl
1. Combustibility: The gas is neither combustible nor a supporter of combustion.
2. Thermal dissociation: On heating above 500°C, it dissociates into hydrogen and chlorine.

3. With metals: Metals which come before hydrogen in the electrochemical series form chlorides with
the liberation of hydrogen.

4. Reaction with ammonia: It combines with ammonia to form dense white fumes of ammonium
chloride..

Hydrochloric Acid

Hydrochloric acid is prepared by dissolving hydrogen chloride gas in water using a special funnel
arrangement because direct absorption of HCl gas in water using a delivery tube causes back suction.

Properties of Hydrochloric Acid
Physical Properties
• Colourless, slightly pungent with sharp sour taste.
• Corrosive in nature and causes blisters on the skin.
• Density is 1.2 gm/cc with boiling point of 110°C.

Chemical Properties
• Monobasic in nature
HCl dissociates in aqueous solution to produce one hydrogen ion [H+] per molecule of the acid.
HCl + H₂O → H₃O+ + Cl−

• Acidic nature
The presence of hydrogen ion [H+] in HCl imparts acidic properties to an aqueous solution of
hydrochloric acid.

• Action on metals
Ca + 2HCl → CaCl₂ + H₂
Mg + 2HCl → MgCl₂ + H₂

• Action on oxides and hydroxides
MgO + 2HCl → MgCl₂ + H₂O
Ca (OH)2 + 2HCl → CaCl₂ + H₂O

• With salts of weaker acids
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
NaHCO₃ + HCl → NaCl + H₂O + CO₂
Na₂SO₃ + 2HCl → 2NaCl + H₂O + SO₂
NaHSO₃ + HCl→ NaCl + H₂O + SO₂
Na₂S + 2HCl → 2NaCl + H₂S

• Action on thiosulphates
Na₂SO₃ + 2HCl → 2NaCl + H₂O + SO₂ + S
• Reaction with nitrates
AgNO₃ + HCl → AgCl + HNO₃

Oxidation of Hydrochloric Acid

Formation of Aqua Regia
Aqua regia is a mixture of one part of conc. nitric acid and three parts of conc. hydrochloric acid.
HNO3 + 3HCl → NOCl + 2H₂O + 2[Cl]
The nascent chlorine released reacts with noble metals such as gold and platinum to give their soluble
chlorides.
Au + 3[Cl] → AuCl₃
Pt + 4[Cl] → PtCl₄

Uses of Hydrochloric Acid
a. In the manufacture of dyes, drugs, paints and silver chloride.
b. For purifying bone black, because HCl dissolves the calcium phosphate present in bones.
c. To remove rust from iron sheets.