ICSE Class 10 Chemistry Board Exam Question Paper 2022 with Solutions

ICSE Class 10 Chemistry Board Exam Question Paper with Solutions

SECTION A

Question 1
Choose the correct answers to the questions from the given options. (Do not copy the question. Write the correct answer only.)

(i) The ore of aluminium is: [1 Mark]
(a) Calamine
(b) Haematite
(c) Magnetite
(d) Cryolite

Answer: (d) Cryolite

Cryolite (Na₃AlF₆) is a principal ore and flux used in the extraction of aluminium.

Teacher's Note:
a) Remember that bauxite is the chief ore of aluminium, but cryolite is also a significant ore and solvent used in the Hall-Heroult process.
b) Do not confuse haematite (iron ore) or calamine (zinc ore) with aluminium ores.

(ii) Hydrogen chloride gas is not collected over water, as: [1 Mark]
(a) It is highly soluble in water.
(b) It is less soluble in water
(c) It is lighter than air.
(d) It is heavier than air.

Answer: (a) It is highly soluble in water.

Hydrogen chloride gas dissolves extensively in water, forming hydrochloric acid, preventing its collection over water.

Teacher's Note:
a) Gases that are highly soluble in water are typically collected by downward displacement of air.
b) Students must recall solubility properties when choosing the method of gas collection in the laboratory.

(iii) An aqueous solution of ammonia is [1 Mark]
(a) Neutral
(b) Acidic
(c) Basic
(d) Amphoteric

Answer: (c) Basic

Ammonia dissolves in water to form ammonium hydroxide, which releases hydroxyl ions (OH^-) making the solution alkaline or basic.

Teacher's Note:
a) Aqueous ammonia turns red litmus blue, confirming its basic nature.
b) Note that dry ammonia gas is neutral, but its aqueous solution is basic due to ionisation.

(iv) The acid which is least volatile is: [1 Mark]
(a) Hydrochloric acid
(b) Nitric acid
(c) Dilute sulphuric acid
(d) Concentrated sulphuric acid

Answer: (d) Concentrated sulphuric acid

Concentrated sulphuric acid has a very high boiling point and low vapor pressure, making it a non-volatile acid used to prepare volatile acids like HCl and HNO₃.

Teacher's Note:
a) Volatility refers to the tendency of a substance to vaporize easily.
b) Concentrated sulphuric acid is termed non-volatile or least volatile among common mineral acids.

(v) The gas formed, when calcium bisulphite reacts with dilute HNO₃: [1 Mark]
(a) Sulphur trioxide
(b) Hydrogen
(c) Sulphur dioxide
(d) Hydrogen sulphide

Answer: (c) Sulphur dioxide

Action of a dilute acid on a metal sulphite or bisulphite always releases sulphur dioxide gas with its characteristic suffocating smell.

Teacher's Note:
a) Bisulphites react with mineral acids to liberate SO₂ gas.
b) Do not confuse sulphites/bisulphites with sulphides, which liberate hydrogen sulphide gas.

(vi) The IUPAC name of formic acid: [1 Mark]
(a) Propanoic acid
(b) Methanoic acid
(c) Ethanoic acid
(d) Butanoic acid

Answer: (b) Methanoic acid

Formic acid contains a single carbon atom, so its IUPAC name corresponding to the one-carbon alkane root is methanoic acid.

Teacher's Note:
a) Common names like formic acid must be correctly mapped to their IUPAC counterparts (methanoic acid for HCOOH).
b) Ethanoic acid corresponds to acetic acid (CH₃COOH).

(vii) The metallic oxide which when reacts with HCl forms salt and water [1 Mark]
(a) Carbon monoxide
(b) Nitrous oxide
(c) Ammonium hydroxide
(d) Sodium oxide

Answer: (d) Sodium oxide

Sodium oxide is a basic metallic oxide that neutralizes hydrochloric acid to produce sodium chloride salt and water.

Teacher's Note:
a) Basic oxides react with acids to form salt and water only.
b) Carbon monoxide and nitrous oxide are neutral oxides and do not react with dilute acids.

(viii) Vanadium pentoxide is used as a catalyst in the preparation of: [1 Mark]
(a) Nitrogen gas
(b) Nitrogen dioxide gas
(c) Sulphur trioxide gas
(d) Carbon dioxide gas

Answer: (c) Sulphur trioxide gas

In the Contact process for manufacturing sulphuric acid, V₂O₅ catalyzes the oxidation of sulphur dioxide to sulphur trioxide.

Teacher's Note:
a) Vanadium pentoxide (V₂O₅) or platinum can be used, but V₂O₅ is preferred industrially due to lower cost and poison resistance.
b) This is a key catalytic reaction frequently tested in board examinations.

(ix) The catalyst used for the conversion of ethene to ethane: [1 Mark]
(a) Iron
(b) Nickel
(c) Cobalt
(d) Molybdenum

Answer: (b) Nickel

Finely divided nickel (or platinum/palladium) acts as a catalyst for the hydrogenation of alkenes like ethene to alkanes like ethane.

Teacher's Note:
a) Hydrogenation is an addition reaction where hydrogen adds across the double bond in the presence of a metal catalyst.
b) Mentioning the temperature (around 200^ℵC) along with nickel completes the reaction conditions.

(x) Substance which helps to lower the fusion point of the mixture in the Hall Heroult Process: [1 Mark]
(a) Coke
(b) Concentrated sodium hydroxide
(c) Fluorspar
(d) Concentrated potassium hydroxide

Answer: (c) Fluorspar

Fluorspar (CaF₂) and cryolite are added to purified alumina to lower its fusion point and increase electrical conductivity.

Teacher's Note:
a) Pure alumina has a very high melting point above 2000^ℵC; adding fluorspar and cryolite reduces it to about 950^ℵC.
b) Students must clearly distinguish between the roles of cryolite, fluorspar, and powdered coke in electrolytic extraction.

SECTION B

(Attempt any three questions from this section)

Question 2

(i) Define: [2 Marks]
(a) Isomerism

Answer:
The phenomenon in which more than one compound has the same molecular formula but different chemical structures is called isomerism. Chemical compounds that have identical chemical formulae but differ in properties and the arrangement of atoms in the molecule are called isomers.

Teacher's Note:
a) Always include both aspects in the definition: same molecular formula and different structural arrangement.
b) Mention that isomers differ in physical or chemical properties.

(b) Ores [2 Marks]

Answer:
Ores are naturally occurring mineral aggregates containing a high percentage of a particular metal, from which the metal can be extracted commercially and economically.

Teacher's Note:
a) All ores are minerals, but not all minerals are ores.
b) The key term in the definition is economical extraction.

(ii) Name the following: [2 Marks]
(a) The property by which carbon links with itself to form a long chain.

Answer: Catenation

Catenation is the self-linking property of carbon atoms through covalent bonds to form straight chains, branched chains, or rings.

Teacher's Note:
a) Catenation is responsible for the vast number of organic compounds existing in nature.
b) Spelling must be precise (Catenation).

(b) The saturated hydrocarbon having general formula C_nH_2n-2.

Answer: Alkyne

Teacher's Note:
a) The question states "saturated hydrocarbon" due to a printing error in the original paper, but the formula C_nH_2n-2 specifically defines alkynes, which are unsaturated hydrocarbons containing a triple bond.
b) Alkanes are C_nH_2n+2, alkenes are C_nH_2n, and alkynes are C_nH_2n-2.

(iii) Draw the structural diagram of: [3 Marks]
(a) Pentanal

Answer:
H - C(|)(H)(|)(H) - C(|)(H)(|)(H) - C(|)(H)(|)(H) - CH=O (or expanded structural formula showing all single bonds for carbon-carbon backbone and double bond to oxygen).

[Figure: Structural formula showing a chain of 5 carbon atoms, with the terminal carbon having a double bond to an oxygen atom and a single bond to a hydrogen atom, and all other valencies satisfied by hydrogen atoms.]

Teacher's Note:
a) Pentanal is a 5-carbon aldehyde with the functional group -CHO at the end of the chain.
b) Ensure all carbon tetravalency and hydrogen bonds are clearly shown.

(b) Propanol

Answer:
H - C(|)(H)(|)(H) - C(|)(H)(|)(H) - C(|)(H)(|)(H) - OH

[Figure: Structural formula showing a 3-carbon chain with an -OH group attached to the terminal carbon atom, and all remaining bonds saturated with hydrogen atoms.]

Teacher's Note:
a) Propanol (propan-1-ol) has three carbon atoms with an alcoholic hydroxyl group.
b) Drawing lines for every single covalent bond ensures full credit.

(c) 2-butene

Answer:

[Figure: Structural formula showing H₃C - CH = CH - CH₃ with a carbon-carbon double bond between the second and third carbon atoms, and methyl groups at each end with single hydrogen atoms attached to the double-bonded carbons.]

Teacher's Note:
a) 2-butene has a 4-carbon chain with the double bond located between carbon 2 and carbon 3.
b) Check the position of the double bond carefully when drawing.

(iv) Complete and balance the following chemical equations: [3 Marks]
(a) H₂C = CH₂ + Cl₂ - (CCl₄/Inert solvent) →
(b) C₄H₆ + O₂[excess] →
(c) CH₄ + O₂[excess] →

Answer:
(a) H₂C = CH₂ + Cl₂ → CH₂Cl - CH₂Cl
(b) 2C₄H₆ + 11O₂ → 8CO₂ + 6H₂O
(c) CH₄ + 2O₂ → CO₂ + 2H₂O

Teacher's Note:
a) Note that equation (b) in the original key had a typographical stoichiometry error (showing 7O₂ instead of 11O₂ for complete combustion of alkyne/butyne); it has been correctly balanced here.
b) Always double check carbon and hydrogen balance before finalizing combustion equations.

Question 3

(i) State the following: [2 Marks]
(a) A compound formed when excess ammonia gas reacts with chlorine.

Answer:
Ammonium chloride and nitrogen gas are formed when excess ammonia reacts with chlorine.

Teacher's Note:
a) Reaction: 8NH₃ + 3Cl₂ → 6NH₄Cl + N₂.
b) Excess ammonia acts as a reducing agent for chlorine.

(b) A substance added to water, to manufacture sulphuric acid in the Contact process. [1 Mark]

Answer:
Oleum (or concentrated sulphuric acid absorbing sulphur trioxide).

Teacher's Note:
a) SO₃ is not dissolved directly in water because the reaction is violently exothermic and produces an acid fog.
b) Instead, SO₃ is dissolved in concentrated H₂SO₄ to form oleum (H₂S₂O₇), which is then diluted with water.

(ii) Identify the gas P and Q in the reactions given below: [2 Marks]
(a) A compound reacts with an acid to form gas P which has no effect on acidified K₂Cr₂O₇ solution but turns lime water milky.

Answer:
P is Carbon dioxide (CO₂).

Teacher's Note:
a) Carbon dioxide turns lime water milky due to the formation of insoluble calcium carbonate.
b) Unlike sulphur dioxide, CO₂ does not decolourize acidified potassium dichromate solution.

(b) A metallic nitrate reacts on heating gives oxygen gas along with a coloured gas Q. [1 Mark]

Answer:
Q is Nitrogen dioxide (NO₂).

Teacher's Note:
a) Heavy metal nitrates like lead nitrate or copper nitrate on heating decompose to give metal oxide, nitrogen dioxide (reddish brown gas Q), and oxygen gas.
b) NO₂ is characterized by its reddish-brown color.

(iii) State the observation for the following: [3 Marks]
(a) Dry ammonia gas reacts with oxygen in the presence of a catalyst.

Answer:
Reddish-brown vapours of nitrogen dioxide are seen in the flask due to the oxidation of nitric oxide formed during catalytic oxidation.

Teacher's Note:
a) Catalytic oxidation of ammonia produces nitric oxide (NO), which instantly combines with oxygen in air to form reddish-brown NO₂.
b) This is the key initial step of the Ostwald process.

(b) Excess chlorine gas reacts with ammonia gas. [1 Mark]

Answer:
A yellow-colored highly explosive liquid (nitrogen trichloride, NCl₃) is formed.

Teacher's Note:
a) When chlorine is in excess, nitrogen trichloride is produced.
b) When ammonia is in excess, ammonium chloride and nitrogen are produced.

(c) Carbon reacts with hot concentrated nitric acid. [1 Mark]

Answer:
Carbon is oxidized to carbon dioxide, accompanied by the evolution of dense reddish-brown fumes of nitrogen dioxide.

Teacher's Note:
a) Concentrated nitric acid is a strong oxidizing agent.
b) Non-metals like carbon are oxidized to their respective oxides.

(iv) Write balanced equation for the following conversions: [3 Marks]
(a) Carbon from cane sugar and concentrated sulphuric acid.
(b) Ferric nitrate from ferric hydroxide and nitric acid.
(c) Ammonium sulphate from ammonium hydroxide and sulphuric acid.

Answer:
(a) C₁₂H₂₂O₁₁ + H₂SO₄ [conc.] → 12C + 11H₂O + n(H₂SO₄)
(b) Fe(OH)₃ + 3HNO₃ → Fe(NO₃)₃ + 3H₂O
(c) 2NH₄OH + H₂SO₄ → (NH₄)₂SO₄ + 2H₂O

Teacher's Note:
a) Concentrated sulphuric acid acts as a dehydrating agent in reaction (a), removing water molecules from sugar.
b) Ensure equations (b) and (c) are fully balanced for hydrogen, oxygen, and metal/radical ions.

Question 4

(i) State the relevant reason for the following: [2 Marks]
(a) Concentrated alkali is used for the concentration of bauxite ore.

Answer:
Concentrated sodium hydroxide solution dissolves aluminium oxide to form soluble sodium meta-aluminate, leaving insoluble impurities (like iron oxide and silica) behind as red mud, which can be filtered out.

Teacher's Note:
a) This is known as Baeyer's process for purifying bauxite.
b) Amphoteric nature of aluminium oxide allows it to dissolve in caustic alkalis.

(b) Fused alumina is reduced to aluminum by electrolysis. [1 Mark]

Answer:
Alumina is extremely stable thermally and chemically; hence, chemical reducing agents cannot reduce it, requiring electrolytic reduction.

Teacher's Note:
a) Metals at the top of the reactivity series (like Al, Na, Mg) are extracted by electrolytic reduction of their fused salts.
b) Carbon reduction is ineffective for alumina.

(ii) State one use of the given alloys: [2 Marks]
(a) Magnalium

Answer:
Used in the manufacture of aircraft parts and light instruments due to its low density and high strength.

Teacher's Note:
a) Magnalium is an alloy of aluminium and magnesium.
b) Mentioning aircraft construction or scientific instruments secures full marks.

(b) Duralumin [1 Mark]

Answer:
Used for making truck wheels, pressure cookers, and parts of airships and automobiles.

Teacher's Note:
a) Duralumin contains aluminium, copper, magnesium, and manganese.
b) It is prized for its high tensile strength and corrosion resistance.

(iii) Complete the table given below which refers to the laboratory preparation of ammonia gas: [3 Marks]

Answer:
(a) Ammonium chloride (NH₄Cl) and calcium hydroxide [Ca(OH)₂]
(b) Fresh quicklime (CaO)
(c) In an inverted dry gas jar by downward displacement of air.

Teacher's Note:
a) Acidic drying agents like concentrated H₂SO₄ cannot be used because ammonia is basic and would react with them.
b) Quicklime is used as a drying agent since it is basic.

(iv) Identify the terms for the following: [3 Marks]
(a) The process used to purify Alumina by electrolytic reduction.

Answer: Hall-Heroult process (or Heroult process)

Teacher's Note:
a) Hall-Heroult electrolytic cell reduces purified alumina dissolved in molten cryolite.
b) Graphite anodes are consumed during this process.

(b) The experiment used to demonstrate the high solubility of HCl gas. [1 Mark]

Answer: Fountain experiment

Teacher's Note:
a) The fountain experiment also demonstrates the high solubility of ammonia gas.
b) It proves the acidic/alkaline nature of the dissolved gas through indicator color changes.

(c) The chemical property of sulphuric acid forms two types of salts with an alkali. [1 Mark]

Answer: Dibasic nature

Teacher's Note:
a) Sulphuric acid has two replaceable hydrogen ions per molecule, making it dibasic.
b) It forms normal salts and acid salts.

Question 5

(i) Write the balanced chemical equation for the following: [2 Marks]
(a) Action of heat on manganese dioxide and concentrated hydrochloric acid.

Answer:
MnO₂ + 4HCl [conc.] → MnCl₂ + 2H₂O + Cl₂

Teacher's Note:
a) This is a standard laboratory method for preparing chlorine gas.
b) Manganese dioxide acts as an oxidizing agent in this reaction.

(b) Zinc reacts with dilute hydrochloric acid to form zinc chloride. [1 Mark]

Answer:
Zn + 2HCl [dil.] → ZnCl₂ + H₂↑

Teacher's Note:
a) Metals placed above hydrogen in the reactivity series displace hydrogen from dilute acids.
b) Hydrogen gas is evolved with effervescence.

(ii) Select the right answer from the brackets and complete the statements: [2 Marks]
In electrolysis of fused alumina, the anode is made of (a) ____ [gas carbon/graphite] and the product formed at cathode is (b) ____ [oxygen/aluminum].

Answer:
(a) graphite
(b) aluminum

Teacher's Note:
a) Molten aluminium is denser than the electrolyte mixture and collects at the bottom of the cell.
b) Anodes burn away to carbon dioxide and must be replaced periodically.

(iii) Give the IUPAC name for the following: [3 Marks]
(a) H₂C = CH₂
(b) CH₃CH₂CH₂OH
(c) CH₃CH(CH₃)CH₂CH₂CH₃

Answer:
(a) Ethene
(b) Propan-1-ol (or Propanol)
(c) 2-methylpentane

[Figure: Structural diagrams for (a) ethene, (b) propan-1-ol, and (c) 3-methylpentane as printed in the question.]

Teacher's Note:
a) Numbering of carbon chains must start from the end closer to the functional group or double bond.
b) For branched alkanes, identify the longest continuous carbon chain and locate substituent positions correctly.

(iv) Study the diagram, which shows the brown Ring Test and answer the questions given below: [3 Marks]
(a) Which ion is determined by Brown Ring Test?
(b) Why is freshly prepared iron[II] sulphate used in the test?
(c) Name the substance Z.

[Figure: Diagram of a test tube showing a brown ring test setup with a layer of iron(II) sulphate solution, concentrated sulphuric acid at the bottom, and a brown ring at the junction marked Z.]

Answer:
(a) Nitrate ion (NO₃^-)
(b) Because on exposure to the atmosphere, ferrous sulphate gets oxidized to ferric sulphate which will not give the brown ring.
(c) Concentrated sulphuric acid (H₂SO₄)

Teacher's Note:
a) The brown ring is formed due to the complex compound [Fe(H₂O)₅NO]SO₄.
b) Substance Z is added along the sides of the inclined test tube to form a distinct lower layer.

Question 6

(i) Distinguish between the following as directed: [2 Marks]
(a) Sodium sulphite solution and sodium sulphate solution. [using dilute H₂SO₄]

Answer:
When treated with dilute H₂SO₄, sodium sulphite gives off sulphur dioxide gas which has a suffocating smell of burning sulphur and turns acidified potassium dichromate paper green. Sodium sulphate does not react with dilute H₂SO₄ to evolve any gas.

Teacher's Note:
a) Always state the specific reagent, observation (gas evolved), and confirmatory test.
b) Barium chloride solution can also be used as an alternative distinction test.

(b) Lead salt solution and zinc salt solution. [using NH₄OH solution in excess] [2 Marks]

Answer:
Lead salt solution gives a chalky white precipitate of lead hydroxide with ammonium hydroxide, which is insoluble in excess NH₄OH. Zinc salt solution gives a gelatinous white precipitate of zinc hydroxide which is soluble in excess NH₄OH to form a clear solution.

Teacher's Note:
a) Solubility of precipitates in excess reagent is a classic analytical chemistry diagnostic test.
b) Lead hydroxide is insoluble in excess ammonium hydroxide, whereas zinc hydroxide dissolves.

(ii) Give one word for the following statements: [2 Marks]
(a) The compounds of various metals found in nature with earthly impurities
(b) A homogeneous mixture of two or more metals or a metal and a non-metal in specific ratios.

Answer:
(a) Minerals
(b) Alloy

Teacher's Note:
a) Minerals are naturally occurring inorganic substances.
b) Alloys improve physical properties like hardness, tensile strength, and corrosion resistance compared to pure metals.

(iii) Identify the acid in each case: [3 Marks]
(a) The acid formed when sulphur reacts with concentrated nitric acid.
(b) An acid, which on adding to lead nitrate solution produces a white precipitate which is soluble on heating.
(c) The acid formed when potassium nitrate reacts with a least volatile acid.

Answer:
(a) Sulphuric acid (H₂SO₄)
(b) Hydrochloric acid (HCl) [Note: Lead chloride precipitates out and dissolves on heating]
(c) Nitric acid (HNO₃)

Teacher's Note:
a) Lead chloride (PbCl₂) is soluble in hot water and precipitates as white needles upon cooling.
b) Non-volatile concentrated sulphuric acid reacts with potassium nitrate to produce volatile nitric acid.

(iv) Match column A with column B: [3 Marks]

Answer:

Teacher's Note:
a) Matching questions require correct pairing of homologous series with their characteristic functional groups.
b) Double-check the bond lines (e.g., -CHO for aldehyde, -COOH for carboxylic acid, -OH for alcohol).