Chemistry End-of-Year Exam 2024

Which of the following best describes a pure substance?

• A A colourless solution obtained from filtration.

• B A green solid that melts at exactly 45°C.

• C A white solid with a density of 2 g/cm³.

• D A white solid that dissolves partially in water.

An experimental setup is shown in the diagram. Sulfur dioxide, SO₂, was placed inside the porous pot. The water level at X falls, then rises and returns to X after a period of time. Which gas represents Y?

• A Cl₂

• B CO₂

• C N₂O₄

• D SO₃

Liquids X and Y are immiscible. • X has a higher boiling point than Y. • X has a lower density than Y. X and Y can be separated from each other both by fractional distillation and by use of a separating funnel. Which row correctly gives the first liquid to be collected by fractional distillation and the lower liquid in the separating funnel?

• A X X

• B X Y

• C Y X

• D Y Y

Which statement about an atom is correct?

• A Each element has only one nucleon number.

• B The nucleon number can be less than the proton number.

• C The nucleon number and proton number can be the same.

• D The number of neutrons is never equal to the number of electrons.

Two isotopes of carbon, C-12 and C-13 are found combined in a giant molecule. The average relative atomic mass of carbon in the giant molecule is 12.4. What is the proportion of C-12 atoms in the giant molecule?

• A 50%

• B 60%

• C 70%

• D 80%

A compound of a covalent oxide has the chemical formula X₂O. What could be the electronic configuration of atom X?

• A 2.4

• B 2.8.1

• C 2.8.6

• D 2.8.7

Which statement best explains why calcium oxide has a higher melting point than sodium oxide?

• A The covalent bonds in calcium oxide are stronger than the ionic bonds in sodium oxide.

• B The electrostatic forces of attraction in calcium oxide are stronger than that in sodium oxide.

• C The intermolecular forces of attraction in calcium oxide are stronger than that in sodium oxide.

• D The metallic bonds in calcium oxide are stronger than that in sodium oxide.

Which substance contains both ionic and covalent bonds?

• ammonium chloride

• calcium oxide

• sulfur dichloride

• silicon dioxide

Which of the following substances is most likely a metal?

• can be bent and pulled into wires easily

• can conduct electricity in solid state only

• has a crystalline appearance

• has a melting point of 20 °C

An oxide compound contains 18.5% by mass of calcium and 51.9% by mass of iron. What is its empirical formula?

• CaFe₂O

• CaFe₂O₄

• Ca₂FeO₂

• Ca₄Fe₂O