ICSE 2025 – Chemistry Paper

Maximum Marks: 80
Time Allowed: Two hours

General Instructions

  • Answers to this Paper must be written on the paper provided separately.

  • You will not be allowed to write during the first 15 minutes.

  • This time is to be spent in reading the question paper.

  • The time given at the head of this Paper is the time allowed for writing the answers.

  • Section A is compulsory.

  • Attempt any four questions from Section B.

  • The intended marks for questions or parts of questions are given in brackets [ ].

ICSE 2025 Chemistry Paper - Section A

Section A (40 Marks)

(Attempt all questions from this section. Do not copy the questions. Write the correct answers only.)

Question 1

(i). Which gas decolourises potassium permanganate (KMnO₄) solution?
(a) Sulphur dioxide
(b) Ammonia
(c) Hydrogen chloride
(d) Carbon dioxide
Answer: ____________
(ii) Which formula represents a saturated hydrocarbon?
(a) C₄H₈
(b) C₅H₁₂
(c) C₄H₆
(d) C₅H₁₀
Answer: ____________
(iii). The metal whose oxide can be reduced by common reducing agents:
(a) Copper
(b) Sodium
(c) Aluminium
(d) Potassium
Answer: ____________
(iv). An organic compound has a vapour density of 22. The molecular formula is:
[ Atomic weight: C=12, H=1]
(a) CH₄
(b) C₂H₄
(c) C₂H₆
(d) CH₃
Answer: ____________
(v). In the reaction, sulphuric acid acts as a:
S + 2H₂SO₄ → 3SO₂ + 2H₂O
(a) Non-volatile acid
(b) Dibasic acid
(c) Oxidising agent
(d) Reducing agent
Answer: ____________
(vi). Assertion (A): Tendency of losing electrons increases down the group.
Reason (R): The most reactive metal is at the top of Group 1.
(a) Both A and R are true, R is the correct explanation of A
(b) Both A and R are true, R is not the correct explanation A
(c) A is true, R is false
(d) A is false, R is true
Answer: ____________
(vii). The ore that can be concentrated by magnetic separation:
(a) Corundum
(b) Haematite
(c) Calamine
(d) Bauxite
Answer: ____________
(viii). The diagram given below shows the bonding in covalent molecule AB2.
Diagram description
Which option represents correct electronic configuration of atoms A and B before combining together to form the above molecule?
A B
(a) 2,4 2,8,6
(b) 2,4 2,8,7
(c) 2,8 2,8,8
(d) 2,6 2,8,7
Answer: ____________
(ix). Which of the following options has compounds of the same homologous series?
(a) CH₄, C₂H₆, C₃H₈
(b) CH₄, C₂H₆, C₅H₆
(c) C₃H₄, C₃H₆, C₃H₈
(d) C₄H₄, C₃H₆, C₇H₁₀
Answer: ____________
(x). Assertion (A): In the Contact Process, SO3 is not directly dissolved in water to obtain sulphuric acid.
Reason (R): Dense fog or misty droplets of sulphuric acid are formed which are difficult to condense.
(a) Both (A) and (R) are true, and (R) explains (A)
(b) Both (A) and (R) are true, but (R) does not explain (A)
(c) (A) is true, (R) is false
(d) (A) is false, (R) is true
Answer: ____________
(xi). Given below are the four ions:
Cl-, Li+, Al3+, K+
Identify the pair of ions which have the same electronic configuration:
(Atomic numbers: Cl = 17, Li = 3, Al = 13, K = 19)
(a) Cl- and Li+
(b) Al3+ and K+
(c) Cl- and K+
(d) Li+ and K+
Answer: ____________
(xii). Which pair of reactants can best be used to produce lead (II) sulphate?
(a) Sulphuric acid + Lead
(b) Sulphuric acid + Lead hydroxide
(c) Sodium sulphate + Lead nitrate
(d) Potassium sulphate + Lead oxide
Answer: ____________
(xiii). aqueous copper (II) sulphate is electrolysed using copper electrodes.
Which statement about the electrolysis is NOT correct?
(a) An oxidation reaction occurs at the positive electrode.
(b) The current is carried through the electrolyte by ions.
(c) The positive electrode loses mass.
(d) The number of copper (II) ions in the electrolyte decreases.
Answer: ____________
(xiv). X, Y and Z are three metallic atoms in the same group, 'X' has the smallest atomic radius. Which is the best reducing agent?
(a) X
(b) Y
(c) Z
(d) All three have the same reducing power
Answer: ____________
(xv). 40 cm3 of methane is reacted with 60 cm3 of oxygen.
The equation of the reaction is given below:
CH4 + 2O2 → CO2 + 2H2O
All volumes are measured in room temperature. What is the total volume of gases remaining?
(a) 60 cm3
(b) 40 cm3
(c) 45 cm3
(d) 50 cm3
Answer: ____________
ICSE 2025 Chemistry Paper - Section A

Question 2

(i) A student was instructed to prepare and collect ammonia gas using aluminium nitride. The student set up the apparatus as shown below. Study the given diagram and answer the following questions. [5]

(a) Name the substance X added through the thistle funnelby the student.
(b) Write a balanced chemical equation for the reaction occuring between Aluminium nitride and substance X.
(c) Identify the substance Y.
(d) State the function of Y.
(e) Why could the student not collect ammonia gas at the end of experiment?

(ii) State the terms for the following: [5]

(a) Undistilled alcohol containing a large amount of methanol.
(b) A salt formed by the partial replacement of hydroxyl group of a di-acidic or tri-acidic base by an acid radical.
(c) Organic compounds having the same molecular formula but different structural formula.
(d) The tendency of an atom to attract the shared electrons towards itself when combined in a compound.
(e) The type of covalent bond in which electrons are shared unequally between the combining atoms.

(iii) Complete the following sentences by choosing the correct words from brackets. [5]
(a) ______ solution forms coloured precipitate with ammonium hydroxide which is soluable in excess ammonium hydroxide (Ferrous chloride / Copper nitrate)
(b) Zinc blende is converted to zinc oxide by ______ (Calcination / Roasting)
(c) ______ conducts electricity by movement of ions. (Molten iron / Molten sodium chloride )
(d) The reaction that takes place at the anode during electrolysis of aqueous Sodium argentocyanide with silver electrodes is ______
( Ag → Ag⁺ + e⁻ / Ag⁺ + e⁻ → Ag )
(e) The salt formed from ZnO reacts with hot concentrated NaOH is ______ (Sodium zincate / Zinc hydroxide)

(iv) Match the Column A with Column B: [5]
Column A Column B
(a) N2 + 3H2 ⇌ 2NH3 1. Vanadium Pentoxide
(b) 4NH3 + 5O2 → 4NO + 6H2O 2. Nickel
(c) 2SO2 + O2 ⇌ 2SO3 3. Iron
(d) CH4 + H2 → C2H6 4. Concentrated Sulphuric Acid
(e) CuSO4·5H2O → CuSO4 + 5H2O 5. Platinum

(v) (a) Draw the structural diagram of the following organic compounds: [5]
1. 2-methyl propene
2. butanal

    (b) Give IUPAC name of the following organic compounds:

ICSE 2025 Chemistry Paper - Section B

Section B (40 Marks)

(Attempt any four questions from this Section.)

Question 3

(i) The atomic number of two atoms X and Y are 14 and 8 respectively. [2]
State:
  1. The period to which X belongs.
  2. The formula of the compound formed between X and Y.
    (Do not identify X and Y)
(ii) Justify the following statements: [2]
  1. Anode is known as the oxidizing electrode.
  2. Graphite electrodes are preferred in the electrolysis of molten lead bromide.

(iii)The reaction between concentrated sulphuric acid and magnesium can be represented by the equation given below: [3]

Mg + 2H2SO4 → MgSO4 + 2H2O + SO2

If 60 g of magnesium is used in the reaction, calculate the following:
  1. The mass of sulphuric acid needed for the reaction.
  2. The volume of sulphur dioxide gas liberated at S.T.P.
    (Atomic weight: Mg = 24, H = 1, S = 32, O = 16)
(iv) Give one significant observation when: [3]
  1. A solution of barium chloride is added to zinc sulphate solution.
  2. Lead nitrate is heated in a test tube.
  3. Chlorine gas is passed over moist starch iodide paper.

Question 4

(i) A gas cylinder can hold 150 g of hydrogen under certain conditions of temperature and pressure. If an identical cylinder with the same capacity can hold 450 g of gas G under the same conditions of temperature and pressure, find:[2]

  1. The vapour density of the gas G.
  2. The molecular weight of gas G.

(ii) Complete and balance the following equations:[2]

  1. CH3COONa + NaOH
    CaO
    →
    ??
  2. CH3COOH + Mg → ?

(iii) Name the gas produced during each of the following reactions: [3]

  1. When copper is treated with hot, concentrated nitric acid.
  2. When ammonia is burnt in an atmosphere of oxygen.
  3. When ferrous sulphide reacts with dilute hydrochloric acid.

(iv)Study the table given below. Use only the letters given in the table to answer the questions. Do not identify the elements. [3]

  1. State the valency of element G.
  2. Which element can exhibit catenation?
  3. Write the formula of the compound formed between M and P.

Question 5

(i) Given below are two sets of elements from two different periods: [2] Name the element with the highest ionisation potential in each of the following sets.

  1. Al, Cl, Mg
  2. Ne, O, F

(ii) Ammonia gas is passed over heated copper (II) oxide in a combustion tube: [2]

  1. Name the gas evolved.
  2. What will be the colour of the residue that is left in the combustion tube at the end of the reaction?

(iii) Give balanced equations for the following: [3]

  1. Action of dilute hydrochloric acid on ammonium carbonate.
  2. Oxidation of sulphur with hot concentrated nitric acid.
  3. Reaction of concentrated sulphuric acid with carbon.

(iv) Rohit took two different salt solutions in test tubes C and D as shown in the figure below. [3]
He added dilute HCl to each of the two test tubes. The products formed in the test tubes C and D are silver chloride and lead chloride respectively.

  1. State one common observation made by Rohit in both the reactions.
  2. State the observations made by him on addition of excess of ammonium hydroxide to the products formed in:
    • Test tube C
    • Test tube D

Question 6

(i) Given below is a diagram showing the placement of five different oxides. With respect to the given diagram, answer the following questions:[3]

  1. Name the type of oxide represented in region X in the diagram.
  2. Identify the oxide which has been incorrectly placed in the above diagram.
  3. Name the oxide from the above diagram which will form an alkali when dissolved in water.

(ii) Given below are organic compounds labelled A to F.[3] Answer the questions that follow:

  1. Which compound forms a single product with bromine?
  2. Which two compounds have the same molecular formula?
  3. Which two compounds will react together in the presence of concentrated H2SO4 to form a product with a fruity smell?

(iii) An organic compound ‘X’ contains carbon, oxygen and hydrogen only. The percentage of carbon and hydrogen are 47.4% and 10.5% respectively. The relative molecular mass of ‘X’ is 76.Find the empirical formula and the molecular formula of ‘X’ .[4]

[Atomic weight: C = 12, O = 16, H = 1]

Question 7

(i) Seema added a few pieces of copper turnings to a test tube containing concentrated acid P and she noticed that a reddish-brown gas evolved.[2]

  1. Name the acid P used by Seema.
  2. Write a balanced chemical equation for the reaction that took place.

(ii) Answer the following questions with reference to the concentration of bauxite ore. [2]

  1. Name the process used to concentrate the ore.
  2. Give a balanced chemical equation for the conversion of aluminium hydroxide to pure alumina.

(iii) Draw the dot and cross structure of the following: [3]

  1. An ionic compound formed when Mg reacts with dilute HCl.
  2. A covalent compound formed when H2 reacts with Cl2.
  3. The positive ion produced when ammonia gas is dissolved in water.
    (Atomic number: Mg = 12, Cl = 17, H = 1, N = 7)

(iv) Acidulated water is electrolysed using platinum electrodes.[3]

  1. Why is dilute sulphuric acid added to water?
  2. Write the reaction taking place at the cathode.
  3. What is the observation at the anode?

Question 8

(i) [2]

  1. State Avogadro’s Law.
  2. Define Co-ordinate bond.

(ii) Differentiate between the following pairs of compounds using the reagent given in the bracket:[2]

  1. Ammonium chloride and Sodium chloride (using an alkali)
  2. Zinc Nitrate solution and Calcium Nitrate solution (using excess sodium hydroxide solution)

(iii) You are provided with some compounds in the box.[3]

PbO, CH4, HCl, PbO2, NCl3, SO2, CO2

Choose the most appropriate compound which fits the descriptions (a) to (c) given below: [3]

  1. A colourless gas which turns acidified K2Cr2O7 from orange to green.
  2. A yellow explosive oily liquid formed when excess chlorine gas reacts with ammonia gas.
  3. A yellow metallic oxide formed on thermal decomposition of PbCO3.

(iv) P, Q, R, S are the different methods of preparation of salts: [3]

  • P – Simple displacement
  • Q – Neutralisation by titration
  • R – Precipitation
  • S – Direct combination

Choose the most appropriate method to prepare the following salts:

  1. PbCl2
  2. FeCl3
  3. Na2SO4