ICSE Class 10 Chemistry (Science Paper – 2) Solved Paper 2024

(a) Addition reaction

Explanation:

Unsaturated hydrocarbons contain carbon-carbon double or triple bonds. These bonds undergo addition reactions.

(d) Completely filled

Explanation:

Neon has a completely filled outermost shell, so removing an electron requires maximum energy.

(c) Bronze

Explanation:

Bronze is an alloy of 80% copper, 2% Zinc and 18% Tin.

(c) Aluminium hydroxide

Explanation:

As Al(OH)₃ is amphoteric in nature, it can generate salt and water as well as behave as a base with a strong acid.

(b) Esterification

Explanation:

The reaction of an alcohol with a Carboxylic acid in the presence of conc. H2SO4 forms an ester. This is called an esterification reaction.

(a) Dehydration

Explanation:

Dehydration involves elimination of elements of water from alcohol. Conc. sulphuric acid acts as dehydrating agent.

\mathrm{C_2H_5OH} \xrightarrow[\;170^\circ\mathrm{C}\;]{\mathrm{Conc.\ H_2SO_4\ [excess]}} \mathrm{C_2H_4} + \mathrm{H_2O}

(b) Sulphuric acid

Explanation:

Sulphuric acid donates oxygen atoms to sulphur, leading to the formation of SO₂ and water (H₂O). Thus, sulphuric acid acts as an oxidizing agent.

(d) Bromine

Explanation:

Electron affinity tends to be highest for elements on the right side of the periodic table. Therefore, Bromine (Br) is likely to have the highest electron affinity.

(b) NaAlO₂

Explanation:

In the standard Hall-Heroult process, the electrolytic mixture consists of 20% alumina (Al₂O₃), 60% cryolite (Na₃AlF₆) and 20% fluorspar (CaF₂). Hence, NaAlO₂ is not a part of the electrolytic mixture.

(c) Reducing property

Explanation:

Ammonia reduces Black Copper [II] oxide to reddish brown copper as shown in the below equation:

\mathrm{2NH_3 + 3CuO \rightarrow 3Cu + 3H_2O + N_2 \uparrow}

(b) H₂S gas

Explanation:

The rotten egg smell is commonly associated with Hydrogen sulphide (H2S) gas. H2S is a colourless gas and is known for its strong, unpleasant odour, similar to that of rotten eggs.

(c) Lighter than air

Explanation:

Ammonia gas is lighter than air and hence collected by the downward displacement of air. Ammonia is not collected over water since it is highly soluble in water.

(b) 1 and 3

Explanation:

(1) The molar mass of O₂ = 2 × atomic mass of oxygen ≈ 32 g/mol.
So, 32 grams of O₂ is equivalent to 1 mole of O₂. 1 mole of any gas at S.T.P. occupies 22.4 liters.

(2) 2 moles of hydrogen gas will occupy 2 x 22.4 = 44.8 litres

(3) 1 mole of NH₃ contains 6.022 × 10²³ molecules and occupies 22.4 liters at S.T.P. Therefore, 6.022 × 10²³ molecules of NH₃ will also occupy 22.4 liters at S.T.P.

(c) Two lone pairs of electrons

Explanation:

Oxygen has six valence electrons. In water it forms two shared pairs and retains two lone pairs.

(b) Ore

Explanation:

Ore is the mineral that contains a high enough concentration of the desired metal. Ores can be economically and conveniently processed to obtain the metal.

(a) In electroplating, the cathode is the electrode where reduction (gain of electrons) occurs. The iron cup is placed at the cathode because the metal ions from the electrolyte will be reduced and deposit onto the iron cup. This process coats the iron cup with a layer of metal, achieving the plating effect.

(b) Ni²⁺ must be present in the electrolyte.

(c) A low current for a longer time should be used as longer time and low current initiates a thicker, uniform deposit.

(d) Ni²⁺ + 2e^– → Ni

(e) The Nickel plate is gradually dissolved as ions in solution.

(a) The salt that can be prepared by Direct Combination is FeCl₃.

(b) The metallic oxide which can be reduced by using common reducing agents is Fe₂O₃.

(c) The metal nitrate which on thermal decomposition forms a black residue is copper nitrate.

(d) During the electrolysis of copper sulphate solution, if copper is used as electrodes, the colour of the electrolyte does not fade.

(e) The process of heating the concentrated ore in a limited supply or absence of air is calcination.

(a) Alkyl group

(b) Electrodes

(c) Mole

(d) Electronegativity

(e) Empirical formula

(a) IUPAC names are:

1. 2,3-Dichloropentane

2. 1-Propanoic acid

(b) Structural formula

1. 3-methyl pentane

2. Propyne

3. Methanal

(a) Concentrated sulphuric acid acts as a dehydrating agent.

(b) Excess of ammonia reacts with chlorine to give ammonium chloride and nitrogen.

(a) The gas that turns lime water milky is carbon dioxide. Since the gas produced is CO₂, the anion in the compound is carbonate (CO₃^2-).

(b) The brown ring test indicates the presence of nitrate ions (NO₃^–).

(a) Magnesium reacts with acids to liberate hydrogen gas. Therefore, Solutions Q (pH 5) and R (pH 2) will react with magnesium to liberate hydrogen gas.

(b) Ammonium chloride reacts with strong bases to release ammonia gas. A solution with a high pH (basic nature) is required for this reaction to take place. Solution P, with a pH of 13, is strongly basic and will liberate ammonia gas when it reacts with ammonium chloride.

(c) Solution Q (pH 5) will contain both molecules (of the weak acid) and ions (hydrogen ions), as it is a moderately acidic solution where some acid will be in molecular form and some in ionic form.

(a) → Contact Process

(b) → Vanadium pentoxide

(c) → Sulphur trioxide (SO₃)

(a) Molar volume — The molar volume of a gas is the volume occupied by one gram-molecular mass or by one mole of the gas at S.T.P. It is equal to 22.4 dm³.

(b) Normal salt — Normal salt is formed by complete replacement of the replaceable hydrogen ion of an acid molecule by a basic radical [metallic or ammonium ion].

(a) Electron dot structure of Methane molecule is shown below:

(b) Electron dot structure of Nitrogen molecule is shown below:

(a) \mathrm{Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O}

(b) \mathrm{C_2H_5COONa + NaOH} \xrightarrow{\mathrm{CaO,\ Delta}} \mathrm{C_2H_6 + Na_2CO_3}

(c) \mathrm{C_2H_4Br_2 + 2KOH\ (alcoholic)} \xrightarrow{\Delta} \mathrm{C_2H_2 + 2KBr + 2H_2O}

(a) Ethanol

(b) Ethanoic acid

(c) Ethene

(a) Aluminium

(b) Iron

(a) When sulphuric acid is added to a solution of barium chloride it reacts with barium chloride to form barium sulphate which is a white precipitate.

\mathrm{H_2SO_4 + BaCl_2 \rightarrow BaSO_4\downarrow + 2HCl}

When nitric acid is added to barium chloride, there is no reaction to form a precipitate because nitric acid does not contain sulphate ions. The solution remains clear.

(b) Unsaturated Hydrocarbons contain one or more double or triple bonds between carbon atoms. Examples include alkenes (with double bonds) and alkynes (with triple bonds). Saturated Hydrocarbons only have single bonds between carbon atoms.

(a) Given,

1 mole of CaCO₃ = molecular mass of CaCO₃ = 100 g

∴ 5 moles of CaCO₃ weighs = 100 x 5 = 500 g

(b) 1 mole of CaCO₃ requires 2 moles of HCl.

∴ 5 moles of CaCO₃ will require 2 x 5 = 10 moles of HCl

(c) 1 mole of CaCO₃ produces 1 mole of CO₂ and 1 mole occupies 22.4 l of volume.

∴ 5 moles of CaCO₃ will produce 5 moles of CO₂ and 5 moles will occupy 22.4 x 5 = 112 L

(a) Carbon dioxide

\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O}

(b) Carbon dioxide

\mathrm{CuCO_3 \rightarrow CuO + CO_2}

(c) Chlorine

\mathrm{MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2}

(a) Y is electrolytic dissociation.

Reason — PbBr₂ is an electrovalent compound and its contains lead [Pb²⁺] and bromide [Br^1-] ions that are held together by an electrostatic force of attraction. Melting causes the separation of these ions. Hence, it exhibits electrolytic dissociation.

(b) X is ionization.

Reason — HCl is a polar covalent compound. In gaseous state or pure liquid state, it does not conduct an electric current. When HCl is added to water, formation of Hydronium [(H₃O)⁺] and Chloride [Cl^–] ions takes place. Hence, it exhibits ionization.

(a) Inert gases have completely filled octet which makes them extremely stable. They neither lose, nor gain electrons. Hence, they do not form ions.

(b) Covalent compounds have low melting and boiling points because they have weak forces of attraction between the binding molecules, thus less energy is required to break the force of bonding.

(a) Beryllium > Carbon > Fluorine

(b) Acetic acid < Sulphuric acid < Phosphoric acid

(c) Potassium < Sodium < Lithium

(a) Hydrogen

(b) Sulphur

(c) Chlorine

(a) The cation present is Ferric (Fe³⁺).

Reason — A reddish-brown precipitate with ammonium hydroxide indicates the presence of Ferric ions. When ammonium hydroxide is added to a solution containing Fe³⁺ ions, a reddish-brown precipitate of Ferric hydroxide forms.

(b) The anion present is Chloride (Cl^–).

Reason — A white precipitate with silver nitrate suggests the presence of Chloride ions (Cl^–). Silver nitrate reacts with chloride ions to form a white precipitate of silver chloride (AgCl).

(a) Carbon tetrachloride is a non-polar covalent molecule.

(b) During electrolysis of acidulated water, the gas liberated at the anode is oxygen.

According to the given equation:

For N₂

4 vol. of NH₃ produce 2 vol. of N₂

∴ 240 cc of NH₃ will produce = \rac{2 \imes 240}{4} = 120 \mathrm{cc of N_2}

For O₂

4 vol. of NH₃ reacts with 3 vol. of O₂

∴ 240 cc of NH₃ will react with = \rac{3 \times 240}{4} = 180 \mathrm{cc of O_2}

Amount of unused Oxygen = 300 cc – 180 cc = 120 cc

Hence, composition of the resultant gaseous mixture at room temperature is 120 cc of O₂ + 120 cc of N₂.

(a) (i) AB

Reason — The valency of A is 2 and the valency of B is 2.

(a) (ii) DC₄

Reason — The valency of D is 4 and the valency of C is 1.

(b) D

Reason — The electronic configuration of D (2,4) suggests that it is Carbon. Carbon exhibits the property of catenation.

(a) Haematite

Explnation: Haematite is an iron ore that can be concentrated by magnetic separation because it contains iron, which is magnetic.

(b) CH

Explnation: Molecular formula of Ethyne is C₂H₂. The simplest whole-number ratio of carbon to hydrogen atoms is 1:1. Therefore, its empirical formula is CH.

(a) \mathrm{Cu} + 4\mathrm{HNO_3 (conc.)} \longrightarrow \mathrm{Cu(NO_3)_2} + 2\mathrm{NO_2} + 2\mathrm{H_2O}

(b) \mathrm{AlN} + 3\mathrm{H_2O} \longrightarrow \mathrm{Al(OH)_3} + \mathrm{NH_3}

(a) \mathrm{NaCl} + \mathrm{H_2SO_4} \xrightarrow{<200^\circ\mathrm{C}} \mathrm{NaHSO_4} + \mathrm{HCl}\uparrow

(b) Hydrogen chloride gas is collected by upward displacement of air.

(c) As conc. H₂SO₄ is non-volatile and has a high boiling point, therefore, it displaces the volatile hydrogen chloride from the salt sodium chloride. Hence, conc. H₂SO₄ is used as a reactant in the laboratory preparation of HCl from sodium chloride. Conc. nitric acid cannot be used in place of conc. H₂SO₄ since it is volatile and may volatize out along with the hydrogen chloride.