- Ostwald Process: Developed in 1914 to make nitric acid from ammonia.
- Step 1: Ammonia + oxygen → nitric oxide (NO) using platinum at 800°C.
- Step 2: NO + O₂ → NO₂ at about 50°C.
- Step 3: NO₂ + water + O₂ → HNO₃ in absorption tower.
- Concentration: 68% acid distilled to 98% (fuming); pure HNO₃ crystallizes at –42°C.
Key Points
Key Points: Nitric Acid
- Formula: Nitric acid (HNO₃), molecular mass 63; nitrogen has valency 5.
- Occurrence: Found in rainwater and in salts like NaNO₃, KNO₃.
- Formation: Lightning forms NO → NO₂ → dissolves in rain → HNO₃.
- Nitrogen Fixation: Converts atmospheric nitrogen into useful nitrates.
- Old Name: Called aqua fortis as it dissolves many metals, even silver.
Key Points: Manufacture of Nitric Acid
Key Points: Physical Properties of Nitric Acid
- Colour: Pure HNO₃ is colourless; commercial (68%) is yellowish brown.
- Smell & Nature: Suffocating smell; fumes in the air and are hygroscopic.
- Boiling/Melting Point: Boils at 86°C, melts at –42°C; 68% forms a constant-boiling mixture at 121°C.
- Solubility & Density: Fully soluble in water; density is 1.54 (pure), 1.42 (68%).
- Effect on Skin: Corrosive; causes yellow stains (xanthoproteic acid).
Key Points: Chemical Properties of Nitric Acid
- Stability: Nitric acid breaks down in sunlight, turning yellow due to NO₂.
- Acidic Nature: Strong acid—reacts with bases, carbonates, and bicarbonates to form nitrates.
- Oxidiser: Acts as a strong oxidising agent; gives off nascent oxygen.
- Reaction with Metals: Most metals react to form nitrates; dilute acid gives NO, concentrated acid gives NO₂.
- Aqua Regia: Mix of HNO₃ and HCl; dissolves gold and platinum using nascent chlorine.
Key Points: Effects of Heat on Nitrates
- NaNO3: Gives nitrites and oxygen on heating.
- Other Metal Nitrates: Form metal oxides, NO₂ (brown gas), and oxygen.
- Ag & Hg Nitrates: Break into metal, NO₂, and oxygen.
- Ammonium Nitrate: Decomposes explosively to give laughing gas (N₂O).
Important Questions [23]
- Distinguish Between the Following Pairs of Compounds Using the Reagent Given in the Bracket.
- State one observation for the following: Concentrated nitric acid is reacted with sulphur.
- Differentiate between the following pairs based on the odourless gas which turns lime water milky and the criteria given: Sulphuric acid and Nitric acid (using barium chloride solution)
- Name the gas evolved when the following mixtures are heated. Sodium Nitrite and Ammonium Chloride
- Give a balanced equation for the following reaction: Copper reacts with concentrated nitric acid.
- Give a balanced chemical equation for Laboratory preparation of Nitric acid.
- Write Balanced Chemical Equations For Action of Hot and Concentrated Nitric Acid on Copper
- Dilute Nitric Acid is Generally Considered a Typical Acid but Not So in Its Reaction with Metals.
- Explain the Following: Concentrated Nitric Add Appears Yellow When It is Left Standing in a Glass Bottle.
- Explain the following: An all-glass apparatus is used in the laboratory preparation of nitric acid.
- Write balanced equations for the action of heat on a mixture of copper and concentrated nitric acid.
- What is the Type of Salt Formed When the Reactants Are Heated at a Suitable Temperature for the Preparation of Nitric Acid?
- Write the equation for the reaction: Aluminum, Nitride and Water.
- Write a Balanced Chemical Equation for the Following: Action of Cold and Dilute Nitric Acid on Copper
- Name the Gas that is Produced in the Given Case: Action of Cold and Dilute Nitric Acid on Copper
- Convert the following reaction into a balanced chemical equation: Ammonia to nitric oxide using oxygen and platinum catalyst.
- State one relevant observation for the following: When crystals of copper nitrate are heated in a test tube.
- Fill in the Blanks Hot, Concentrated Nitric Acid Reacts with Sulphur to Form ______________.
- Fill in the Blanks Cold, Dilute Nitric Acid Reacts with Copper to Give ___________.
- Identify the Substance Underlined: the Dilute Acid Which is an Oxidizing Agent.
- Give a Balanced Chemical Equation for Action of Conc. Nitric Acid on Sulphur
- Write a balanced equation for the action of warm water on magnesium nitride.
- Name the Gas that is Produced in the Given Cases : Sulphur is Oxidized by Concentrated Nitric Acid.
