Cambridge IGCSE Chemistry Pass Exam Papers – 2023 May-June Paper 41


Question 1

  1. Sulfur dioxide.


    Sulfur dioxide (SO₂) is a gas that can dissolve in water to form sulfurous acid, contributing to acid rain formation.

  2. Ammonia.


    Ammonia (NH₃) dissolves in water to form ammonium hydroxide, which is alkaline.

  3. Xenon.


    Xenon is a noble gas and is inert, meaning it does not readily react with other elements or compounds.

  4. Oxygen.


    Oxygen (O₂) is a product of photosynthesis, where plants convert carbon dioxide and water into glucose and oxygen.

  5. Ethene.


    Ethene (C₂H₄) is an unsaturated hydrocarbon that can undergo polymerization to form polymers such as polyethylene.

  6. Ammonia.


    In the test for nitrate ions, ammonia (NH₃) is produced as a byproduct when ammonium compounds are reacted with a strong base like sodium hydroxide.

Question 2

  1. 5 protons, 6 neutrons, and 5 electrons.


    An atom of ¹¹B has 5 protons, 6 neutrons, and 5 electrons.

    1. 20%.


      The relative abundance of ¹⁰B is calculated based on the average atomic mass and the isotopic masses.

    2. \[ \frac{0.540 \text{g}}{10.8} = 0.05 \text{ mol} \]

      \[ 0.05 \text{ mol} \times 6.02 \times 10^{23} = 3.01 \times 10^{22} \text{ atoms} \]


      Using the molar mass of boron and Avogadro’s number, the number of atoms in 0.540 g of boron is calculated.

    1. Bauxite.


      Bauxite is the ore from which aluminum is extracted.

    2. Cryolite.


      Cryolite lowers the operating temperature and improves conductivity during the extraction of aluminum.

    3. Al³⁺ + 3e⁻ → Al


      The ionic half-equation for the reduction of aluminum ions at the cathode.

    4. Carbon reacts with oxygen to form carbon dioxide.


      The carbon anodes react with oxygen formed at the anode to produce carbon dioxide, requiring frequent replacement.

  2. Good conductor of electricity and low density.


    Aluminum is suitable for overhead electrical cables because it conducts electricity well and has a low density.

  3. Aluminum oxide layer is unreactive.


    The oxide layer on aluminum prevents it from reacting with other substances, explaining its apparent unreactivity.

    1. 2Al + 3F₂ → 2AlF₃


      The balanced symbol equation for the reaction between aluminum and fluorine.

    2. Aluminum ion with 8 electrons in the outer shell, fluoride ion with 7 electrons and 1 cross in the outer shell, and charges of 3⁺ on aluminum and 1⁻ on fluoride.


      The electronic configurations of the aluminum ion and fluoride ion, showing the transfer of electrons and resulting charges.

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