Key Points
Key Points: Hydrogen Chloride
- Formula & Mass: Hydrogen chloride has the molecular formula HCl and a molecular mass of 36.5.
- Bond Type: HCl contains a covalent bond between hydrogen and chlorine atoms.
- Discovery: First prepared by Glauber in 1648; later named hydrochloric acid by Davy in 1810.
- Natural Occurrence: Found in volcanic gases as hydrogen chloride gas.
- Biological Role: Hydrochloric acid is present in gastric juice (0.2–0.4%) and aids in digestion.
Key Points: Physical Properties of Hydrogen Chloride Gas
| No. | Property | Description |
|---|---|---|
| 1. | Colour | Colourless gas |
| 2. | Smell | Pungent choking smell |
| 3. | Taste | Sour (acidic) in taste |
| 4. | Physiological nature | It is corrosive in nature. It irritates nose, throat and lungs. |
| 5. | Density | About 1.25 times heavier than air (V.D. of HCl is 18.25; air is 14.4). |
| 6. | Boiling point | –83 °C |
| 7. | Melting point | –113 °C |
| 8. | Liquefaction and solidification | Liquefies to a colourless liquid under 40 atm pressure at 10 °C. |
| 9. | Solubility | Highly soluble in water (1 vol. water dissolves 452 vol. gas); also soluble in non-polar solvents like acetone and toluene. |
Key Points: Chemical Properties of Hydrogen Chloride Gas
- Non‑combustible gas – HCl neither burns nor supports combustion; it extinguishes a burning splint.
- Thermal dissociation – Above 500 °C, HCl decomposes into hydrogen and chlorine gases.
- Reaction with metals – Metals above hydrogen in the reactivity series react with HCl to form metal chlorides and hydrogen gas.
- Acidic nature – HCl readily forms chlorides, showing typical acid behaviour.
- Reaction with ammonia – HCl gas reacts with ammonia gas to produce dense white fumes of ammonium chloride.
Key Points: Physical Properties of Hydrochloric Acid
| Property | Description |
|---|---|
| 1. Colour | Colourless |
| 2. Smell | Pungent choking smell |
| 3. Taste | Sour (acidic) |
| 4. Effect on skin | Concentrated acid is corrosive and causes blisters on the skin |
| 5. Solubility | Readily soluble in water in all proportions |
| 6. Boiling point | 110°C (volatile acid) |
Key Properties: Chemical Properties of Hydrochloric Acid
- Acidic Nature: Aqueous HCl is a strong acid and turns blue litmus red.
- Action on Metals: Reacts with metals above hydrogen to form metal chlorides and hydrogen gas.
- Action on Bases: Reacts with metal oxides and hydroxides to form salt and water (neutralisation).
- Action on Salts: Decomposes carbonates, sulphites, and sulphides to give gases like CO₂, SO₂, or H₂S.
- Precipitation Reactions: Gives white precipitates with AgNO₃ (AgCl) and Pb(NO₃)₂ (PbCl₂); AgNO₃ is a test for chloride ions.
Key Points: Uses of Hydrochloric Acid
- Laboratory Use: Used as a reagent and in the preparation of aqua regia.
- Industrial Manufacturing: Helps produce chlorine, chlorides (e.g., NH₄Cl), dyes, drugs, paints, and photographic chemicals.
- Metal Treatment: Used in pickling steel, removing rust, and cleaning metal surfaces before electroplating or painting.
- Bone and Glue Processing: Purifies bone black and is used in glue extraction from bones.
- Medical Use: Dilute HCl is prescribed to aid digestion in patients with low gastric acid.
Important Questions [25]
- Mangenese Dioxide and Copper (Ii) Oxide. (Using Concentrated Hcl)
- State One Relevant Observation for Given Reactions: Action of Dilute Hydrochloric Acid on Iron (Ii) Sulfide.
- Write Balanced Chemical Equations to Show The Behavior of H2so4 as an Acid When It Reacts with Magnesium
- The Metal Which Does Not React with Water Or Dilute H2so4 but Reacts with Concentrated H2so4 is _________.
- Potassium Sulphite on Reacting with Hydrochloric Acid Releases _______ Gas
- State One Relevant Observation for the Following When Hydrogen Sulfide Gas is Passed Through Lead Acetate Solution
- The Acid on Mixing with Silver Nitrate Solution Produces a White Precipitate Which is Soluble in Excess Ammonium Hydroxide
- Write a balanced equation for the action of dilute hydrochloric acid on sodium sulphide.
- State Your Observation When Moist Starch Iodide Paper is Introduced into Chlorine Gas.
- Name the Gas that is Produced in the Given Cases : Action of Dilute Hydrochloride Acid on Sodium Sulphide.
- Dry Hydrogen Chloride Gas Can Be Collected by ________ Displacement of Air. (Downward / Upward)
- For the Preparation of Hydrochloric Acid in the Laboratory: What Arrangement is Done to Dissolve Hydrogen Chloride Gas in Water?
- Give a Chemical Test to Distinguish Between the Given Pairs of Chemicals: Sodium Chloride Solution and Sodium Nitrate Solution
- State your observation when dilute hydrochloric acid is added to a lead nitrate solution and the mixture is heated.
- State Your Observations When Dilute Hydrochloric Acid is Added to Copper Carbonate
- State Your Observations When Dilute Hydrochloric Acid is Added to Sodium Thiosulphate
- Select from the List the Gas that Matches the Description Given in Case this Gas Has a Characteristic Rotten Egg Smell.
- Study the figure given below and answer the questions which follow: (i) Identify the gas Y. (ii) What property of gas Y does this experiment demonstrate?
- The aim of the Fountain experiment is to prove that ______.
- When Dilute Hcl is Added to a Salt Q, a Brisk Effervescence is Produced and the Gas Turns Lime Water Milky. When Nh4oh Solution is Added to the Above Mixture (After Adding Dilute Hcl), It Produces a White Precipitate Which is Soluble in Excess Nh4oh Solution.
- Select from the List the Gas that Matches the Description Given in Case this Gas Produces Dense White Fumes with Ammonia Gas.
- When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the products formed is ______.
- Differentiate between the following pair based on the criteria given in the bracket: Sulphuric acid and hydrochloric acid [type of salts formed]
- Convert the following reaction into a balanced chemical equation: Ferrous sulphide to hydrogen sulphide using hydrochloric acid.
- The following table is related to an industrial process of an acid. Name of the process Reactant Catalyst Final product (a) SO2 + O2 (b) (c) Identify (a), (b) and (c).
Concepts [11]
- Hydrogen Chloride
- General Preparation of Hydrogen Chloride Gas
- Recognition and Identification of Gases
- Physical Properties of Hydrogen Chloride Gas
- Chemical Properties of Hydrogen Chloride Gas
- Hydrochloric Acid
- Laboratory Method of Preparation of Hydrochloric Acid
- Properties of Hydrochloric Acid > Physical Properties
- Properties of Hydrochloric Acid > Chemical Properties
- Uses of Hydrochloric Acid
- Tests for Hydrogen Chloride and Hydrochloric Acid
