1 Diagram 1 shows the standard representation of element A. What does the number 23 refer to? flag bookmark A Proton number B Nucleon number C Number of electrons D Number of neutrons T4 Chapter 2.3 Atomic Structure The top number in the standard representation is the nucleon number, which is the total number of protons and neutrons. The bottom number 11 is the proton number.
2 Substance A has a melting point of −94.0 °C and a boiling point of 65.0 °C. What is the state of matter of substance A at room temperature? flag bookmark A Solid B Liquid C Gas T4 Chapter 2.1 Basic Concepts of Matter Room temperature is about 25 °C, which lies between the melting point (−94.0 °C) and boiling point (65.0 °C). Therefore, substance A is a liquid.
3 Why is the carbon-12 atom used as the standard atom? - I. Exists as a solid at room temperature - II. Can easily combine with other elements - III. Exists as a non-metal element - IV. Can conduct electricity flag bookmark A I and II B I and III C II and III D III and IV T4 Chapter 3.1 Relative Atomic Mass and Relative Molecular Mass Carbon-12 is chosen because it exists as a solid at room temperature and can easily combine with other elements, making it convenient for standard measurements.
4 Calculate the number of positive ions in 1.5 mol of aluminium oxide. flag bookmark A 6.02 × 10²³ B 6.02 × 10²³ × 1.5 C 6.02 × 10²³ × 1.5 × 3 D 6.02 × 10²³ × 1.5 × 2 T4 Chapter 3.2 Mole Concept T4 Chapter 3.3 Chemical Formula Aluminium oxide has 2 Al³⁺ ions per formula unit, so 1.5 mol contains 1.5 × 2 × 6.02 × 10²³ positive ions.
5 In the Modern Periodic Table, the elements are arranged in order of their flag bookmark A Nucleon number B Number of neutrons C Proton number D Valence electrons T4 Chapter 4.2 The Arrangement in the Periodic Table of Elements Elements in the Modern Periodic Table are arranged by increasing proton number, which defines each element's identity and atomic number. Nucleon number can vary among isotopes, so it is not the basis for arrangement.
6 Which of the following is an ionic compound? flag bookmark A NaCl B NH₃ C HCl D CO₂ T4 Chapter 5.2 Ionic Bond T4 Chapter 5.7 Properties of Ionic Compounds and Covalent Compounds NaCl is ionic because it forms from a metal (Na) and a non-metal (Cl), transferring electrons to create ions. The other options are covalent molecules.
7 Which pair is matched correctly? | | Substance | pH value | |---|---|---| | A | Hydrochloric acid | 4 | | B | Sodium hydroxide | 8 | | C | Ethanoic acid | 6 | | D | Ammonia | 14 | flag bookmark A A B B C C D D T4 Chapter 6.2 pH Value Ethanoic acid is a weak acid, so its pH is slightly below 7, making 6 the most reasonable match. The other pairs give pH values that are too high or too low for their substances.
8 When the temperature of a reacting mixture increases, the rate of reaction increases. Which statement explains why the rate of reaction increases? flag bookmark A The total surface area of the reactant particles increases B The total number of reactant particles per unit volume increases C The reactant particles move faster and collide more often with one another D The reactant particles which collide more often are able to overcome a lower activation energy T4 Chapter 7.4 Collision Theory Higher temperature makes reactant particles move faster, so they collide more often, increasing the rate. Activation energy does not change with temperature.
9 Which composite material contains a mixture of glass and silver chloride? flag bookmark A Fibre glass B Optical fibre C Photochromic glass D Borosilicate glass T4 Chapter 8.4 Composite Materials and Its Importance Photochromic glass contains silver chloride dispersed in glass, which makes it darken when exposed to light and return to clear when light is removed. This is the defining property of this material.
10 Diagram 10 shows the properties of substance X. - Inert towards chemical reactions - A good electrical insulator - High heat resistance - Porous Substance X is probably a type of flag bookmark A Alloy B Glass C Ceramic D Metal T4 Chapter 8.3 Composition of Ceramics and Its Uses Ceramics are inert, electrically insulating, heat-resistant, and porous, so the properties directly match substance X.