Sulphuric Acid Class 10 ICSE — Chemistry Chapter 11

Sulphuric acid Class 10 ICSE chemistry is the subject of this chapter, and the textbook opens it with two names for the acid. The chapter explains the acid’s Middle Ages history, its laboratory preparations, and the Contact process that manufactures it on an industrial scale. It then separates the properties of the dilute acid from those of the concentrated acid. The closing sections list the industrial uses and the tests that identify sulphate salts.

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Download the Sulphuric Acid Class 10 ICSE Chemistry chapter PDF to revise offline or print for practice. It is the full chapter as printed in the book — 9 pages, 8 sections, 20 questions.

What is inside Chapter 11

9 pages · 8 sections · 20 exercise questions

• Intext Questions: 3 questions
• EXERCISE: 17 questions

11.1 INTRODUCTION

Sulphuric acid is called the King of Chemicals because no other manufactured compound serves so many key industries. That is the chapter’s opening claim, and the in-text questions ask you to comment on the name. The second name, oil of vitriol, has a different origin. In the later Middle Ages, heating crystals of green vitriol gave an oily viscous liquid, and that liquid was called oil of vitriol.

The preparation began with green vitriol, which is the crystalline ferrous sulphate heptahydrate. On heating, the crystals break down and give sulphur trioxide among the products:

2\mathrm{FeSO}_4 \cdot 7\mathrm{H}_2\mathrm{O} \xrightarrow{\Delta} \mathrm{Fe}_2\mathrm{O}_3 + \mathrm{SO}_2 + \mathrm{SO}_3 + 14\mathrm{H}_2\mathrm{O}

\mathrm{SO}_3 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_2\mathrm{SO}_4

The pair of equations is the section’s pattern. Sulphur trioxide is the bridge between the two steps. The worked pattern with your own numbers: 1 mol of sulphur trioxide (80 g) dissolves in water to form 1 mol of the acid (98 g). Both names test the same idea, where the substance came from and what it does for industry.

11.2 OCCURRENCE

Sulphuric acid occurs in two states. In the free state, it is found in certain mineral springs, formed by the action of water on certain sulphides. In the combined state, it is present as three sulphate minerals. The chapter lists the minerals with their formulas:

• Barytes: \mathrm{BaSO}_4
• Gypsum: \mathrm{CaSO}_4 \cdot 2\mathrm{H}_2\mathrm{O}
• Kieserite: \mathrm{MgSO}_4 \cdot \mathrm{H}_2\mathrm{O}

There are no equations in this section, so the work is remembering which sulphate goes with which mineral. All three share the sulphate group; the metal and the water of crystallisation change. The pattern to spot is the metal, barium for Barytes, calcium for Gypsum, magnesium for Kieserite. Practise the pair in both directions, name to formula, and formula to name.

11.3 PREPARATION OF SULPHURIC ACID

This section gives three laboratory methods, and each is a small equation set. The first method oxidises an aqueous solution of sulphur dioxide. The oxidising agent may be oxygen, chlorine or bromine:

2\mathrm{SO}_2 + 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{SO}_4

\mathrm{SO}_2 + 2\mathrm{H}_2\mathrm{O} + \mathrm{Cl}_2 \rightarrow \mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{HCl}

\mathrm{SO}_2 + 2\mathrm{H}_2\mathrm{O} + \mathrm{Br}_2 \rightarrow \mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{HBr}

In the chlorine and bromine cases, the colour of the halogen fades as it is consumed. That colour change is the observation to quote. The second method uses sulphur with concentrated nitric acid:

\mathrm{S} + 6\mathrm{HNO}_3 \rightarrow \mathrm{H}_2\mathrm{SO}_4 + 6\mathrm{NO}_2 + 2\mathrm{H}_2\mathrm{O}

The third method dissolves sulphuryl chloride in water:

\mathrm{SO}_2\mathrm{Cl}_2 + 2\mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_2\mathrm{SO}_4 + 2\mathrm{HCl}

All three are laboratory preparations. The industrial route is the Contact process, kept as a separate section after this one. The common thread of the first method is the oxidation of an aqueous solution of sulphur dioxide. Keep the laboratory set separate from the industrial process in your notes.

11.4 MANUFACTURE OF SULPHURIC ACID (CONTACT PROCESS)

The Contact process is the industrial heart of this chapter. Everything runs along one chain: \mathrm{SO}_2 \rightarrow \mathrm{SO}_3 \rightarrow \mathrm{H}_2\mathrm{SO}_4. Follow the five steps in order, and keep the conditions of each step attached to its equation.

Step 1: Production of sulphur dioxide

Sulphur dioxide is produced by roasting metallic sulphides in air, or by burning Louisiana sulphur in purified air. The roasting of iron pyrites is the ore route:

4\mathrm{FeS}_2 + 11\mathrm{O}_2 \rightarrow 2\mathrm{Fe}_2\mathrm{O}_3 + 8\mathrm{SO}_2

\mathrm{S} + \mathrm{O}_2 \rightarrow \mathrm{SO}_2

The worked pattern follows the pyrites equation. The coefficients read 4 to 8, so 1 mol of iron pyrites gives 2 mol of sulphur dioxide. The burning-sulphur route uses simpler numbers but the same idea, one sulphur to one dioxide.

Step 2: Purification of gases

The sulphur dioxide-air mixture carries dust, moisture and arsenic oxide. Every impurity has to go, otherwise the catalyst loses its efficiency. The gas passes through an electric precipitator, a chamber with wires at high electric potential that attracts and removes solid particles. A water scrubber then frees it from dust.

A drying chamber, using a spray of concentrated sulphuric acid, removes moisture. An arsenic purifier, packed with ferric hydroxide, removes every trace of arsenic oxide. A testing box checks purity by passing light through a darkened box.

Each plant part does one job, in this order: blower, sulphur or iron pyrite burners, dusting chamber, cooling pipes, scrubbing tower, drying tower, arsenic purifier, testing box, contact tower, absorption tower and dilution tank.

Step 3: Catalytic oxidation of sulphur dioxide

The clean, dry mixture passes through the contact tower. The tower is packed with vanadium pentoxide or platinum on perforated shelves. The catalyst sits in vertical iron pipes inside a cylindrical iron tower called the converter. The conversion is the key equation of the chapter:

2\mathrm{SO}_2 + \mathrm{O}_2 \underset{450^\circ\mathrm{C}}{\overset{\mathrm{V}_2\mathrm{O}_5}{\rightleftharpoons}} 2\mathrm{SO}_3

The reaction is highly exothermic. The catalyst is therefore heated only at the start, to about 450°C. The heat of the reaction maintains the temperature afterwards.

Four conditions control the yield, and each has a reason in the chapter:

• Low temperature: exothermic reactions favour low temperatures. The maximum yield sits near 410-450^\circ\mathrm{C}.
• Pressure of 1–2 atmospheres: high pressure favours the reaction because the product occupies less volume than the reactants. Acid-resistant towers that can take high pressure are hard to build.
• Excess of oxygen: more oxygen increases the production of sulphur trioxide.
• A suitable catalyst: platinum is more efficient but expensive and easily poisoned by arsenic(III) oxide, so vanadium pentoxide is used.

Step 4: Absorption of sulphur trioxide

The gas is cooled in a heat exchanger, then passed into the absorption tower. There it meets a descending stream of 98% concentrated sulphuric acid:

\mathrm{SO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{H}_2\mathrm{S}_2\mathrm{O}_7 \quad (\text{oleum or pyrosulphuric acid})

Sulphur trioxide is not absorbed directly in water. The chapter gives the reason: it does not dissolve satisfactorily, it gives out a lot of heat, and it forms misty droplets of sulphuric acid. The two-step route avoids that problem.

Step 5: Dilution of oleum

Oleum moves to the dilution tank, where a calculated amount of water is added. The final acid can be made to any desired strength:

\mathrm{H}_2\mathrm{S}_2\mathrm{O}_7 + \mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{H}_2\mathrm{SO}_4

The whole process summarises in one chain: \mathrm{S} \rightarrow \mathrm{SO}_2 \rightarrow \mathrm{SO}_3 \rightarrow \mathrm{H}_2\mathrm{S}_2\mathrm{O}_7 \rightarrow \mathrm{H}_2\mathrm{SO}_4. Write this chain at the start of a Contact process answer, then expand each stage.

11.5 PROPERTIES OF SULPHURIC ACID

Properties open with a fact that surprises many students. Pure, 100% hydrogen sulphate is not an acid, because it does not ionise. Dissolved in water, it forms hydronium ions and shows acidic properties. The ionisation happens in two stages:

\mathrm{H}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{H}_3\mathrm{O}^+ + \mathrm{HSO}_4^-

\mathrm{HSO}_4^- + \mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{H}_3\mathrm{O}^+ + \mathrm{SO}_4^{2-}

Because it ionises in two stages, sulphuric acid is a dibasic acid. It can form two series of salts, such as sodium sulphate and sodium hydrogen sulphate. The dilution rule follows the same heat idea. Water is never poured on the acid: the large heat evolved turns the added water into steam, which spurts the acid out and can burn.

The safe method is to pour the acid slowly into water with continuous stirring, so the heat spreads through the water and the spurting is minimised. The chemical properties differ sharply between the dilute and the concentrated acid, so the rest of the chapter studies each form separately.

11.5.1 Physical properties

The physical properties are eleven facts in the textbook. The numbers are the part students mix up, so keep the set straight as you read the table.

The boiling point deserves special attention. The acid boils at 338°C, which is what makes it non-volatile. Later in the chapter, that same property is used to prepare volatile acids from their salts. Keep the three numbers distinct: density 1.85 g/cc, melting point 10.4°C, boiling point 338°C.

11.5.2 Chemical properties

(a) Properties of dilute sulphuric acid

Dilute sulphuric acid ionises to a great extent, so it behaves as a strong acid. It shows five acid reactions. Each produces a salt and a second product, and each has a family equation you can adapt.

(1) Reaction with metals above hydrogen. At ordinary temperature, metals above hydrogen in the activity series give the metal sulphate and hydrogen gas. Magnesium is the textbook example:

\mathrm{Mg} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{MgSO}_4 + \mathrm{H}_2 \uparrow

The worked pattern applies the same logic to a metal the textbook does not list. Aluminium also sits above hydrogen, so it displaces hydrogen too:

2\mathrm{Al} + 3\mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Al}_2(\mathrm{SO}_4)_3 + 3\mathrm{H}_2 \uparrow

The reasoning is the activity series: aluminium above hydrogen, so the dilute acid gives the salt and hydrogen. The note to keep is that noble metals like gold and platinum do not react with the acid under any condition.

(2) Neutralisation of bases. The acid neutralises oxides and hydroxides to form salt and water: \mathrm{CuO} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{CuSO}_4 + \mathrm{H}_2\mathrm{O}. Sodium hydroxide can form either the normal salt or the acid salt: \mathrm{NaOH} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{H}_2\mathrm{O}, or 2\mathrm{NaOH} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Na}_2\mathrm{SO}_4 + 2\mathrm{H}_2\mathrm{O}. The chapter shows the same pattern for FeO.

(3) Carbonates and bicarbonates. The acid liberates carbon dioxide from carbonates and bicarbonates. The family pattern is carbonate plus acid to salt, water and carbon dioxide:

\mathrm{Na}_2\mathrm{CO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Na}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2 \uparrow

Bicarbonates follow the same shape, with two bicarbonate units needed per acid. The chapter also lists 2\mathrm{NaHCO}_3 and 2\mathrm{KHCO}_3 with their carbon dioxide outputs.

(4) Sulphides. Metal sulphides give hydrogen sulphide gas: \mathrm{FeS} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{FeSO}_4 + \mathrm{H}_2\mathrm{S} \uparrow. The pattern repeats for sodium sulphide and zinc sulphide, each giving its sulphate and \mathrm{H}_2\mathrm{S}.

(5) Sulphites and bisulphites. These give sulphur dioxide:

\mathrm{Na}_2\mathrm{SO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Na}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow

The chapter adds a warning: sulphur dioxide is poisonous and harms health and vegetation, so it pollutes the environment.

The common mistakes in this section come from mixing the two forms of the acid:

• Copper with dilute acid gives no hydrogen. Copper lies below hydrogen in the activity series. It reacts only with hot concentrated acid, and the gas then is sulphur dioxide, not hydrogen.
• Concentrated acid is a weak acid and a weak electrolyte. Dilute acid is the strong one. Students often swap the two.
• Concentrated acid cannot dry \mathrm{H}_2\mathrm{S}. It oxidises the gas to sulphur instead: \mathrm{H}_2\mathrm{S} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{S} + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow.
• \mathrm{SO}_2 from a sulphite shows the acidic property; \mathrm{SO}_2 from copper shows the oxidising property. The gas is the same, but the property differs.

(b) Properties of concentrated sulphuric acid

Concentrated acid is a weak acid, but it has four characteristic properties that most questions target. Each property has its own reaction family.

(1) Non-volatile nature

Concentrated sulphuric acid boils at 338°C, so it is a non-volatile acid. Heated with a salt of a volatile acid, it displaces that acid by double decomposition. The volatile acid escapes as gas, while the non-volatile acid stays behind. The textbook examples are hydrogen chloride, nitric acid and acetic acid:

\mathrm{NaCl} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{HCl} \uparrow

\mathrm{NaNO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{HNO}_3

\mathrm{CH}_3\mathrm{COONa} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{CH}_3\mathrm{COOH}

This is the property behind the laboratory preparation of HCl and HNO₃. The nitric acid reaction is carried further in the Class 10 ICSE Chemistry chapter on nitric acid, which starts from the same displacement.

(2) As an oxidising agent

On heating, concentrated sulphuric acid decomposes and releases nascent oxygen:

\mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 + [katex display="true"]\mathrm{O}[/katex]

That nascent oxygen oxidises non-metals, metals and inorganic compounds. Carbon gives carbon dioxide, sulphur gives sulphur dioxide, phosphorus gives phosphoric acid:

\mathrm{C} + 2\mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{CO}_2 + 2\mathrm{H}_2\mathrm{O} + 2\mathrm{SO}_2 \uparrow

\mathrm{S} + 2\mathrm{H}_2\mathrm{SO}_4 \rightarrow 3\mathrm{SO}_2 + 2\mathrm{H}_2\mathrm{O}

Copper and zinc behave alike, giving the metal sulphate, water and sulphur dioxide:

\mathrm{Cu} + 2\mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{CuSO}_4 + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow

Inorganic compounds oxidise as well. Hydrogen bromide goes to bromine, hydrogen sulphide goes to sulphur:

2\mathrm{HBr} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Br}_2 + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow

\mathrm{H}_2\mathrm{S} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{S} + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow

Sulphur dioxide itself is both an oxidising and a reducing agent. In the presence of moisture it bleaches temporarily, turning coloured material colourless, and the colour returns in air. The chapter notes that this bleaching is weaker than chlorine’s, so it is used for delicate materials like wet flower petals or fresh grass.

(3) As a dehydrating agent

Concentrated acid has a strong affinity for water. It removes the elements of hydrogen and oxygen from compounds, which is dehydration. Organic acids are dehydrated to carbon oxides:

\mathrm{HCOOH} \xrightarrow{\text{Conc. } \mathrm{H}_2\mathrm{SO}_4} \mathrm{CO} + \mathrm{H}_2\mathrm{O}

(\mathrm{COOH})_2 \xrightarrow{\text{Conc. } \mathrm{H}_2\mathrm{SO}_4} \mathrm{CO} + \mathrm{CO}_2 + \mathrm{H}_2\mathrm{O}

Ethanol loses water to form ethene at 170°C:

\mathrm{C}_2\mathrm{H}_5\mathrm{OH} \xrightarrow[katex display="true"]170^\circ\mathrm{C}{\text{Conc. } \mathrm{H}_2\mathrm{SO}_4} \mathrm{C}_2\mathrm{H}_4 \uparrow + \mathrm{H}_2\mathrm{O}[/katex]

Carbohydrates char. Glucose removes six waters, and cane sugar removes eleven:

\mathrm{C}_{12}\mathrm{H}_{22}\mathrm{O}_{11} \xrightarrow{\text{Conc. } \mathrm{H}_2\mathrm{SO}_4} 12\mathrm{C} + 11\mathrm{H}_2\mathrm{O}

The observation when acid meets sugar: a black spongy mass of carbon rises up, steam is given off, and the whole mass heats because the reaction is exothermic. The carbon left is very pure and is called sugar charcoal. The acid also removes water of crystallisation. Blue \mathrm{CuSO}_4 \cdot 5\mathrm{H}_2\mathrm{O} turns white anhydrous copper sulphate when a few drops of concentrated acid are added.

(4) Preparation of insoluble sulphates

Sulphuric acid precipitates the insoluble sulphates of lead, barium and calcium from their salt solutions. Lead nitrate gives lead sulphate, and barium chloride gives barium sulphate:

\mathrm{Pb}(\mathrm{NO}_3)_2 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{PbSO}_4 \downarrow + 2\mathrm{HNO}_3

\mathrm{BaCl}_2 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 \downarrow + 2\mathrm{HCl}

The chapter closes the chemical properties with a side-by-side comparison. The table is the revision key for this ICSE chapter:

11.6 USES OF SULPHURIC ACID

The uses organise the acid’s jobs into five groups. The first group is gas preparation: halogens, carbon monoxide, carbon dioxide, hydrogen and sulphur dioxide. The second is metallurgy. Sulphates formed with metallic compounds give pure metals on electrolysis, and the acid is used for pickling, removing oxide and carbonate impurities from a metal surface before galvanizing. The third use is in lead accumulators, where the acid undergoes electrolysis in the aqueous state.

The fourth is oil refining, where the acid removes harmful impurities from petrol, kerosene and lubricants.

The fifth group is industrial manufacture, and the list grows long here. The acid goes into:

• Fertilizers: ammonium sulphate, superphosphate of lime.
• Artificial fibres: rayon and nylon.
• Dyes and drugs from coal tar derivatives.
• Explosives: TNT, picric acid, tri-nitro glycerine.
• Acids: nitric acid, hydrochloric acid, phosphoric acid, acetic acid.
• Compounds: sodium sulphate for the glass industry, ferrous sulphate for the ink industry.

Notice the pattern: the acid appears once in the preparation of many products. This ICSE Class 10 chapter lists the uses as a table, so the memory task is grouping, not guessing.

SULPHATES

The closing part of the chapter gives three test reactions. They identify sulphur dioxide, hydrogen chloride and sulphate salts.

Test for sulphur dioxide. Copper turnings heated with concentrated sulphuric acid evolve sulphur dioxide:

\mathrm{Cu} + 2\mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{CuSO}_4 + 2\mathrm{H}_2\mathrm{O} + \mathrm{SO}_2 \uparrow

The gas turns acidified potassium dichromate solution from orange to green. That colour change shows the reducing property of sulphur dioxide:

\mathrm{K}_2\mathrm{Cr}_2\mathrm{O}_7 + \mathrm{H}_2\mathrm{SO}_4 + 3\mathrm{SO}_2 \rightarrow \mathrm{Cr}_2(\mathrm{SO}_4)_3 + \mathrm{K}_2\mathrm{SO}_4 + \mathrm{H}_2\mathrm{O}

Test for hydrogen chloride. Sodium chloride heated with concentrated sulphuric acid gives pungent fumes of HCl gas:

\mathrm{NaCl} + \mathrm{H}_2\mathrm{SO}_4 \xrightarrow{\Delta} \mathrm{NaHSO}_4 + \mathrm{HCl} \uparrow

A glass rod dipped in ammonium hydroxide, held in the gas, gives dense white fumes of ammonium chloride:

\mathrm{HCl} + \mathrm{NH}_4\mathrm{OH} \rightleftharpoons \mathrm{NH}_4\mathrm{Cl} + \mathrm{H}_2\mathrm{O}

Test for a sulphate. Barium chloride solution added to sulphuric acid or to any soluble metal sulphate gives a white precipitate of barium sulphate:

\mathrm{BaCl}_2 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 \downarrow + 2\mathrm{HCl}

\mathrm{BaCl}_2 + \mathrm{MgSO}_4 \rightarrow \mathrm{BaSO}_4 \downarrow + \mathrm{MgCl}_2

The precipitate is insoluble in mineral acids such as hydrochloric acid or nitric acid. This one fact separates a sulphate from a sulphite:

Both precipitates look alike, both white. Only the acid test tells them apart, so the exam asks it as a distinguish question.

What to practise from Sulphuric Acid Class 10 ICSE

The chapter carries two question blocks. The in-text questions test the names of the acid, the Contact process and the arsenic oxide purification. The main exercise works through the same ideas with more writing.

• Intext Questions — 3 questions.
• EXERCISE — 17 questions, including board questions from 2008 to 2014.

The reprinted board questions keep returning to one format. A reaction is given, and the student names the property that makes it happen. The choices are acid, oxidising agent, dehydrating agent or non-volatile acid. Here are the 2012 reprints matched to the property each tests:

Practise this matching format until it is automatic. For every equation in the chapter, ask which property it shows before you move on.

For the full set, browse the Class 10 ICSE Chemistry chapter list. The ICSE Class 10 book hub holds the other subjects. The current syllabus and exam format are published on the official CISCE website.

Sulphuric Acid Class 10 ICSE frequently asked questions

Why is water not poured into concentrated sulphuric acid to dilute it?

Because the large amount of heat evolved turns the poured water into steam. The steam causes the acid to spurt out and can burn the skin. Add the acid slowly to water with continuous stirring instead, so the heat spreads through the water and the spurting is minimised.

Why is sulphur trioxide absorbed in concentrated sulphuric acid and not directly in water?

Sulphur trioxide does not dissolve satisfactorily in water, gives out a lot of heat, and forms misty droplets of sulphuric acid. The Contact process therefore absorbs the trioxide in 98% sulphuric acid to form oleum, \mathrm{H}_2\mathrm{S}_2\mathrm{O}_7, then dilutes the oleum with a calculated amount of water.

How can you distinguish dilute sulphuric acid from dilute hydrochloric acid?

Add barium chloride solution to each. Dilute sulphuric acid gives a white precipitate of barium sulphate, \mathrm{BaSO}_4, which stays undissolved in mineral acids. Dilute hydrochloric acid gives no white precipitate with barium chloride.

Which property of sulphuric acid is used to prepare HCl and HNO₃?

The non-volatile nature of the concentrated acid. Its boiling point is 338°C, so heating it with a chloride or a nitrate drives off the volatile acid: \mathrm{NaCl} + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{HCl}, and \mathrm{NaNO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{NaHSO}_4 + \mathrm{HNO}_3.

What are the key reactions to remember for sulphuric acid class 10 ICSE?

Learn each reaction with its property. The Contact process chain is 2\mathrm{SO}_2 + \mathrm{O}_2 \rightleftharpoons 2\mathrm{SO}_3, then \mathrm{SO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{H}_2\mathrm{S}_2\mathrm{O}_7, then \mathrm{H}_2\mathrm{S}_2\mathrm{O}_7 + \mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{H}_2\mathrm{SO}_4. The dilute acid gives hydrogen with metals above hydrogen, carbon dioxide with carbonates, hydrogen sulphide with sulphides, and sulphur dioxide with sulphites. The concentrated acid chars sugar, oxidises copper and sulphur, and displaces HCl and HNO₃ from their salts.

Reference: ICSE Class 10 Chemistry textbook material, chapter 11: Sulphuric Acid — CISCE-aligned.

More from this book

• Chapter 2: Chemical Bonding
• Chapter 5: Mole Concept and Stoichimetry
• Chapter 8: Study of Compounds Hydrogen Chloride
• Chapter 9: Study of Compounds Ammonia
• Chapter 10: Study of Compounds Nitric Acid