Nitric Acid Class 10 ICSE — Rachna Chapter 10
Nitric acid class 10 ICSE in the Rachna Sagar Chemistry book covers one of the most important acids in the syllabus. This chapter is part of the ICSE Class 10 Chemistry book set. It explains how nitric acid got its name aqua fortis, how it forms in acid rain, and how it is prepared in the laboratory. It then walks through Ostwald’s process and the reactions that make nitric acid a strong oxidizing agent.
Download Nitric Acid Class 10 ICSE Chemistry Chapter 10 PDF
Download the Nitric Acid Class 10 ICSE Chemistry chapter PDF from the Rachna Sagar textbook to revise offline or print for practice. It is the full chapter as printed in the book — 11 pages, 2 sections, 42 questions.
What is inside Chapter 10
11 pages · 2 sections · 42 exercise questions
| Section | Title |
|---|---|
| 1 | Nitric Acid |
| 2 | Flow Chart for the Manufacture of Nitric acid By Ostwald's Process |
- PREVIOUS YEARS' QUESTIONS: 31 questions
- ANSWERS: 11 questions
1 Nitric Acid
Nitric acid is commonly called aqua fortis, meaning strong water. The chemist Glauber first prepared it by distilling nitre with concentrated sulphuric acid. Traces reach the earth through acid rain, which forms by three reactions.
Lightning combines nitrogen and oxygen into nitric oxide. The oxide oxidises to nitrogen dioxide, which dissolves in rainwater to give nitric acid.
\mathrm{N}_{2} + \mathrm{O}_{2} \xrightarrow{\text{thunder/lightning}} 2\mathrm{NO}
2\mathrm{NO} + \mathrm{O}_{2} \longrightarrow 2\mathrm{NO}_{2}
4\mathrm{NO}_{2} + 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2} \longrightarrow 4\mathrm{HNO}_{3}
In the laboratory, nitric acid is made by distilling sodium nitrate or potassium nitrate with concentrated sulphuric acid. Below 200 °C the product is the hydrogen sulphate salt. Above 200 °C it is the normal sulphate.
\mathrm{NaNO}_{3} + \mathrm{H}_{2}\mathrm{SO}_{4} \text{ (conc.)} \xrightarrow{\text{below } 200^\circ\mathrm{C}} \mathrm{NaHSO}_{4} + \mathrm{HNO}_{3}
2\mathrm{NaNO}_{3} + \mathrm{H}_{2}\mathrm{SO}_{4} \text{ (conc.)} \xrightarrow{\text{above } 200^\circ\mathrm{C}} \mathrm{Na}_{2}\mathrm{SO}_{4} + 2\mathrm{HNO}_{3}
Worked pattern: take 170 g of sodium nitrate, which is two moles. Below 200 °C each mole reacts with one mole of concentrated sulphuric acid. Each mole gives one mole of nitric acid, 63 g, so two moles give 126 g.
Above 200 °C the same two moles react with only one mole of acid. The nitric acid yield stays the same, but the salt is now the normal sulphate.
The mixture must not be heated beyond 200 °C. Nitric acid decomposes above this temperature.
4\mathrm{HNO}_{3} \longrightarrow 4\mathrm{NO}_{2} + 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2}
The sulphate also forms a hard crust that sticks to the glass and damages it. A common mistake is to think that heating harder speeds up the preparation. It does not — it destroys the nitric acid you have just made.
The apparatus must be made entirely of glass. The vapours of nitric acid are corrosive, so they damage rubber and cork. Pure nitric acid is colourless, while the commercial sample is pale yellow because it holds dissolved nitrogen dioxide.
Nitric acid is manufactured by Ostwald’s process in three stages. In the first stage, ammonia undergoes catalytic oxidation over platinum at 800 °C. The ammonia itself is covered in the earlier chapter on ammonia in this book.
4\mathrm{NH}_{3} + 5\mathrm{O}_{2} \xrightarrow[katex display="true"]800^\circ\mathrm{C}{\mathrm{Pt}} 4\mathrm{NO} + 6\mathrm{H}_{2}\mathrm{O}[/katex]
In the second stage, the gases cool before entering the oxidation chamber. Nitric oxide oxidises completely at 50 °C.
2\mathrm{NO} + \mathrm{O}_{2} \xrightarrow{50^\circ\mathrm{C}} 2\mathrm{NO}_{2}
In the third stage, nitrogen dioxide rises through an absorption tower packed with quartz. Water trickles down and absorbs it. The quartz provides a large surface area for contact.
4\mathrm{NO}_{2} + 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2} \longrightarrow 4\mathrm{HNO}_{3}
2 Flow Chart for the Manufacture of Nitric acid By Ostwald’s Process
Nitric acid is unstable and decomposes slightly even at room temperature. Heating speeds this up.
4\mathrm{HNO}_{3} \xrightarrow{\Delta} 2\mathrm{H}_{2}\mathrm{O} + 4\mathrm{NO}_{2} + \mathrm{O}_{2}
Nitric acid is a typical monobasic acid. It shows the usual properties of a dilute acid. With indicators, blue litmus turns red, phenolphthalein stays colourless, and methyl orange turns red.
It neutralises metallic oxides and hydroxides to form salt and water.
\mathrm{CuO} + 2\mathrm{HNO}_{3} \longrightarrow \mathrm{Cu(NO}_{3})_{2} + \mathrm{H}_{2}\mathrm{O}
\mathrm{NaOH} + \mathrm{HNO}_{3} \longrightarrow \mathrm{NaNO}_{3} + \mathrm{H}_{2}\mathrm{O}
It reacts with carbonates and bicarbonates to liberate carbon dioxide.
\mathrm{NaHCO}_{3} + \mathrm{HNO}_{3} \longrightarrow \mathrm{NaNO}_{3} + \mathrm{H}_{2}\mathrm{O} + \mathrm{CO}_{2}
\mathrm{Na}_{2}\mathrm{CO}_{3} + 2\mathrm{HNO}_{3} \longrightarrow 2\mathrm{NaNO}_{3} + \mathrm{H}_{2}\mathrm{O} + \mathrm{CO}_{2}
Nitric acid is a strong oxidizing agent. It oxidises non-metals such as carbon, phosphorus, and sulphur. Each reaction produces nitrogen dioxide.
\mathrm{C} + 4\mathrm{HNO}_{3} \text{ (conc.)} \longrightarrow \mathrm{CO}_{2} + 4\mathrm{NO}_{2} + 2\mathrm{H}_{2}\mathrm{O}
\mathrm{P} + 5\mathrm{HNO}_{3} \text{ (conc.)} \longrightarrow \mathrm{H}_{3}\mathrm{PO}_{4} + 5\mathrm{NO}_{2} + \mathrm{H}_{2}\mathrm{O}
\mathrm{S} + 6\mathrm{HNO}_{3} \text{ (conc.)} \longrightarrow \mathrm{H}_{2}\mathrm{SO}_{4} + 6\mathrm{NO}_{2} + 2\mathrm{H}_{2}\mathrm{O}
Because it is an oxidizing agent, nitric acid does not liberate hydrogen with metals. Only magnesium and manganese react with very dilute nitric acid to give hydrogen. Use the mnemonic M and M to remember the pair.
\mathrm{Mg} + 2\mathrm{HNO}_{3} \text{ (v. dil.)} \longrightarrow \mathrm{Mg(NO}_{3})_{2} + \mathrm{H}_{2}
\mathrm{Mn} + 2\mathrm{HNO}_{3} \text{ (v. dil.)} \longrightarrow \mathrm{Mn(NO}_{3})_{2} + \mathrm{H}_{2}
With other metals, nitric acid gives ammonium nitrate or oxides of nitrogen, depending on concentration. Copper shows the clearest difference.
| Property | Dilute nitric acid | Concentrated nitric acid |
|---|---|---|
| Equation | 3\mathrm{Cu} + 8\mathrm{HNO}_{3} \longrightarrow 3\mathrm{Cu(NO}_{3})_{2} + 4\mathrm{H}_{2}\mathrm{O} + 2\mathrm{NO} | \mathrm{Cu} + 4\mathrm{HNO}_{3} \longrightarrow \mathrm{Cu(NO}_{3})_{2} + 2\mathrm{H}_{2}\mathrm{O} + 2\mathrm{NO}_{2} |
| Gas liberated | Nitric oxide, NO | Nitrogen dioxide, NO₂ |
| Observation | Blue solution, colourless gas | Blue solution, reddish brown gas |
A common mistake is to write hydrogen as the gas when copper reacts with nitric acid. Copper never liberates hydrogen. Only magnesium and manganese with very dilute acid do.
Nitric acid also oxidises hydrogen sulphide to sulphur. It is used to make dyes, paints, fertilizers, and aqua regia. The nitrate ion is identified by the brown ring test, which detects NO₃⁻.
\mathrm{H}_{2}\mathrm{S} + 2\mathrm{HNO}_{3} \text{ (conc.)} \longrightarrow 2\mathrm{H}_{2}\mathrm{O} + 2\mathrm{NO}_{2} + \mathrm{S}
What to practise from Nitric Acid Class 10 ICSE
This ICSE chapter carries two exercise blocks. Work through both after reading the sections.
- PREVIOUS YEARS’ QUESTIONS — 31 questions
- ANSWERS — 11 questions
The previous years’ questions repeat a few themes. Expect the all glass apparatus and its reason, the 200 °C limit with its two reasons, copper with dilute and concentrated acid, the Ostwald catalyst platinum, the three acid rain equations, and the brown ring test. You can find the full Class 10 ICSE books list on this site.
Nitric Acid Class 10 ICSE frequently asked questions
Why must the laboratory preparation of nitric acid use an all glass apparatus?
The vapours of nitric acid are corrosive. They damage rubber and cork, so any part made of those materials would be destroyed during the distillation.
Why is the reaction mixture not heated above 200 degrees Celsius?
Two reasons. Nitric acid decomposes above 200 °C into nitrogen dioxide, water, and oxygen. The sulphate also forms a hard crust that sticks to the glass and is difficult to remove.
Which metals liberate hydrogen with very dilute nitric acid?
Only magnesium and manganese. Remember the mnemonic M and M. Other metals give oxides of nitrogen or ammonium nitrate instead of hydrogen.
What is the difference between dilute and concentrated nitric acid with copper?
Dilute acid gives nitric oxide, a colourless gas. Concentrated acid gives nitrogen dioxide, a reddish brown gas. Both give a blue copper nitrate solution.
What are the most repeated questions for nitric acid class 10 icse boards?
The all glass apparatus, the 200 °C limit, copper with dilute and concentrated acid, the Ostwald catalyst, and the brown ring test appear most often. The three acid rain equations are also asked repeatedly. The CISCE website lists the syllabus these questions follow.
Reference: ICSE Class 10 Chemistry textbook material, chapter 10: Nitric Acid — CISCE-aligned.
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