1 Which of the following is the main function of cosmetics? flag bookmark A To treat all skin diseases B To cleanse and beautify oneself C To replace the function of medicine D To provide energy to the body T5 Chapter 5.4 Medicines and Cosmetics Cosmetics are meant for cleansing and beautifying, not for medical treatment, replacing medicine, or supplying energy.
2 Diagram 1 shows the standard representation of the atoms X element and Y element. > ²³₁₁X ²⁴₁₂Y Which of the following statements is **true** regarding these particles? flag bookmark A Atom X and atom Y are isotopes B Atom Y has the same number of neutrons as atom X C Ion X⁺ has the same number of electrons as atom Y D Ion Y²⁺ has the same number of electrons as atom X T4 Chapter 2.3 Atomic Structure Atom X has 11 protons and 12 neutrons; atom Y has 12 protons and 12 neutrons. Therefore, they have the same number of neutrons.
3 Diagram 2 shows a light bulb containing gas X. Which of the following is the property of gas X that enables it to be used in the bulb? flag bookmark A Has a very low boiling point. B Provides an inert atmosphere. C Reacts with the tungsten filament at high temperatures. D Exists as a diatomic molecule at room temperature. T4 Chapter 4.3 Elements in Group 18 Gas X is inert, so it prevents the tungsten filament from reacting with oxygen at high temperatures, thus extending its life.
4 Diagram 3 shows the standard representation of 3 atom of elements. > ²³₁₁P ¹⁶₈Q ¹⁴₇S Which of the following is the formula of the compound formed? flag bookmark A P₂Q B P₂S C QS D SQ T4 Chapter 2.3 Atomic Structure T4 Chapter 3.3 Chemical Formula P loses 1 electron (valency 1) and Q gains 2 electrons (valency 2), so two P⁺ ions combine with one Q²⁻ ion to form P₂Q.
5 What is the process that converts unsaturated fat into saturated fat? flag bookmark A Esterification B Hydrolysis C Hydrogenation D Oxidation T5 Chapter 5.1 Oils and Fats Hydrogenation adds hydrogen atoms to the carbon-carbon double bonds in unsaturated fats, converting them into single bonds to form saturated fats.
6 Hydrated copper(II) nitrate crystals have the formula Cu(NO₃)₂.3H₂O with a relative formula mass of 242. What is the relative atomic mass of copper? [Relative atomic mass: N = 14, O = 16, H = 1] flag bookmark A 56 B 64 C 65 D 70 T4 Chapter 3.1 Relative Atomic Mass and Relative Molecular Mass Ar(Cu) = 242 − [2(14 + 3×16) + 3(2 + 16)] = 242 − 178 = 64. So B is correct.
7 What is the effect of alloying pure gold? flag bookmark A Become harder B Easier to be shaped C Easier to melt D Become more reactive T4 Chapter 8.1 Alloy and Its Importance Alloying pure gold introduces other atoms that disrupt its regular crystal lattice, making it harder and more durable than pure gold.
8 Table 1 shows the pH values of lemon juice. | Substance | pH value | |---|---| | Lemon juice | 2.0 | Which of the following statements is true when lemon juice is diluted? flag bookmark A The pH value of lemon juice will increases B The pH value of lemon juice will decreases C The concentration of hydrogen ions, H⁺ increases D The concentration of hydroxide ions, OH⁻ increases T4 Chapter 6.2 pH Value Diluting lemon juice lowers the concentration of H⁺ ions, so the pH increases toward 7.
9 The statement below describes acid X. > "Acid X is the third member of homologous series of the carboxylic acid." Which of the following is the molecular formula for acid X? flag bookmark A C₂H₅COOH B C₃H₇COOH C C₃H₈O D C₂H₄O₂ T5 Chapter 2.2 Homologous Series The first three carboxylic acids are HCOOH, CH₃COOH, and C₂H₅COOH, so the third member is C₂H₅COOH.
10 Diagram 4 shows a pair of spectacles made from special lenses. The lenses of these glasses are made of a type of glass that turns dark when exposed to sunlight. What is chemical causes the phenomenon? flag bookmark A CuCl B PbO C AgCl D SiO₂ T4 Chapter 8.4 Composite Materials and Its Importance Silver chloride (AgCl) is photochromic: sunlight breaks it into silver and chlorine, causing the lenses to darken and then reverse when light fades.