1 Table 1 shows the number of protons and number of neutrons for atoms W, X, Y and Z. | Atom | Number of protons | Number of neutrons | |---|---|---| | W | 10 | 10 | | X | 11 | 12 | | Y | 12 | 12 | | Z | 17 | 18 | Based on the information in Table 1, which atom can form a negative ion? flag bookmark A W B X C Y D Z T4 Chapter 2.3 Atomic Structure Atom Z has 17 protons and forms a stable negative ion because it needs one more electron to complete its octet.
2 Two atoms of element X have the same mass as one copper atom. What is the relative atomic mass of X? [Relative atomic mass: Cu = 64] flag bookmark A 8 B 16 C 32 D 64 T4 Chapter 3.1 Relative Atomic Mass and Relative Molecular Mass Two X atoms together equal the mass of one copper atom (64), so one X atom has mass 64 ÷ 2 = 32. Hence the relative atomic mass of X is 32.
3 Heat is absorbed or released during a change of state. Which of the following pairs is correctly matched? flag bookmark A Process: Melting; Heat is released B Process: Boiling; Heat is released C Process: Sublimation; Heat is absorbed D Process: Deposition; Heat is absorbed T4 Chapter 2.1 Basic Concepts of Matter Sublimation is a change from solid to gas, which requires energy, so heat is absorbed. Deposition is the reverse and releases heat.
4 **[Bonus]** (One mole of each gas has the same number of molecules (I) and the same volume (III), but NH₃ has 4 atoms per molecule and CH₄ has 5, and their masses are 17 g and 16 g. The correct set, I and III, is not among the options. Any answer is accepted.) Which quantities are the same for one mole of ammonia (NH_3) and one mole of methane (CH_4) gases? [Relative atomic mass: H = 1, C = 12, N = 14] I Number of molecules II Number of atoms III Volume IV Mass flag bookmark A I and II B I and IV C II and III D III and IV
5 Diagram 1 shows the set-up of the apparatus used to determine the empirical formula of a metal oxide. Which of the following metal oxides is suitable to be used in the experiment? flag bookmark A Magnesium oxide B Copper(II) oxide C Aluminium oxide D Calcium oxide T4 Chapter 3.3 Chemical Formula Hydrogen gas from the zinc and hydrochloric acid reduces copper(II) oxide to copper. Oxides of magnesium, aluminium and calcium are too stable to be reduced by hydrogen.
6 Diagram 2 shows the structure of four atoms. In which sequence will the atoms be arranged in the Periodic Table? flag bookmark A P, Q, R, S B R, P, S, Q C Q, P, S, R D S, R, P, Q T4 Chapter 2.3 Atomic Structure T4 Chapter 4.2 The Arrangement in the Periodic Table of Elements Q has 3 electrons, P has 11, S has 17 and R has 19. In the Periodic Table, atoms are arranged in order of increasing proton number, giving Q, P, S, R.
7 Diagram 3 shows the structural formula of compound T. What is the percentage by mass of carbon in compound T? [Relative atomic mass: H = 1; C = 12] flag bookmark A 85.71% B 82.79% C 21.42% D 20.69% T4 Chapter 3.1 Relative Atomic Mass and Relative Molecular Mass Compound T has 4 carbon atoms and 8 hydrogen atoms, so total mass is 48 + 8 = 56. Percentage of carbon = (48 ÷ 56) × 100 = 85.71%.
8 Which of the following statements is true for hydrogen bonds? flag bookmark A Wet pieces of paper stick together because of the hydrogen bonds formed B Hydrogen bonds are formed between hydrogen chloride molecules C Ethane has a higher boiling point than ethanol because ethane can form hydrogen bonds between its molecules D Hydrogen bonds are formed between a hydrogen atom bonded to an atom of high electronegativity such as bromine T4 Chapter 5.4 Hydrogen Bond In wet paper, water molecules form hydrogen bonds with cellulose fibres, creating adhesive forces that stick the paper fibres together.
9 Diagram 4 shows some types of compounds. Which compounds are soluble in water? flag bookmark A I and II B I and IV C II and III D III and IV T4 Chapter 5.7 Properties of Ionic Compounds and Covalent Compounds A substance dissolves in water when its molecules can form hydrogen bonds with water molecules. Methanol (IV) has an O–H group and methylamine (III) has an N–H group, so both form hydrogen bonds with water and dissolve. The ether (I) has an oxygen atom with lone pairs that can accept hydrogen bonds from water, so it is also soluble. Trifluoromethane (II) cannot. (Note: the answer scheme gives B; on checking, our AI thinks D is more accurate, so both B and D are accepted.)
10 Diagram 5 shows the apparatus set-up and observation for the electrical conductivity of compound A. Table 2 shows information about elements K, L, M and N. | Element | K | L | M | N | |---|---|---|---|---| | Position in the Periodic Table | Period 2, Group 14 | Period 3, Group 2 | Period 3, Group 17 | Period 2, Group 18 | Based on Diagram 5 and Table 2, choose the elements that can react to form compound A. flag bookmark A K and N B L and N C K and M D L and M T4 Chapter 4.2 The Arrangement in the Periodic Table of Elements T4 Chapter 5.1 Basics of Compound Formation T4 Chapter 5.7 Properties of Ionic Compounds and Covalent Compounds The bulb lights up, so compound A must be ionic. Only metal L (Group 2) and non-metal M (Group 17) combine to form an ionic compound; N is a noble gas and does not react.