Chem S3 EOY 2023 GESS Ans

GESS 3EXP CHEM EYE 2023 TKG Answers for 3EXP Chem EYE P1 2023 1. B 11. C 21. A 31. D 2. B 12. C 22. C 32. D 3. C 13. B 23. C 33. B 4. A 14. A 24. C 34. D 5. C 15. B 25. C 35. C 6. D 16. A 26. B 36. D 7. D 17. A 27. B 37. B 8. A 18. B 28. A 38. A 9. A 19. D 29. C 39. C 10. D 20. D 30. A 40. C Qn Ans Explanation 1. B 22.15 cm 3 is accurate to 2 decimal places. Burette should be used as it can record up to 2dp (nearest 0.05 cm 3). Beaker measures approximate volumes. Measuring cylinder measures to the nearest 0.5 cm3. Pipette is only accurate for fixed volumes up to 1dp. 2. B Concentrated sulfuric acid is used to dry acidic gases like sulfur dioxide. 3. C The apparatus shown is for the upward delivery gas collection method. Gas X must be less dense than air to be collected by an inverted gas jar. There is not enough information to deduce the solubility of gas X. 4. A Since solid Y is insoluble in ethanol, filtration can be used to easily separate them. The boiling points given are distractors. 5. C The diagram shows that the entire starting line has dissolved in the solvent and travelled up the chromatogram. This means that Megan did not use a pencil (which is insoluble in water) but instead used a pen (containing ink which is soluble in water).

GESS 3EXP CHEM EYE 2023 TKG 6. D Rf = 7 13 = 0.538 7. D Substance Z is a solid at 179 ºC and a gas at 232 ºC. For option D, substance Z will change from solid to liquid state at 194 ºC and change from liquid to gaseous state at 229 ºC. 8. A Protons and neutrons are found in the nucleus of an atom while electrons are found in the electron shells around the nucleus. 9. A I is correct as the innermost shell can only contain two electrons. II is incorrect as the second shell can contain up to eight electrons. III is incorrect as the electron pairs can be placed at any of the four sides of the atom. IV is incorrect as the electronic structure shown is for an ATOM of J, not an ion. The valence shell of atoms are not always fully-filled. 10. D From the chemical formula XO, we know that the two ions in this ionic compound are X2+ and O2-. Electrons are negatively charged. To form an oxide ion of 2- charge, oxygen atom must gain 2 electrons from an atom of X. Similarly, for X to become X2+ ion, each atom of X must lose 2 electrons. 11. C In A, F- has 10 electrons, Cl- has 18 electrons, and Br- has 36 electrons. In B, H+ has 0 electrons, He has 2 electrons, and N3- has 10 electrons. In C, K+ has 18 electrons, Ca2+ has 18 electrons, and P3- has 18 electrons. In D, Na+ has 10 electrons, Mg2+ has 10 electrons, and S2- has 18 electrons. 12. C Each oxygen atom contains 6 valence electrons. 2 of these are used for bonding with sulfur and 4 are not. Therefore, electrons not used for bonding = 4 + 2 inner shell electrons = 6 13. B Covalent bonds are formed between non-metallic elements. Metals and non-metals form ionic bonds. metal non-metal bonding A calcium bromine ionic B - phosphorus oxygen covalent C strontium sulfur ionic D zinc chlorine ionic

GESS 3EXP CHEM EYE 2023 TKG 14. A In metallic bonding, metal atoms lose their valence electrons to form positive metal ions. The valence electrons which are lost form the ‘sea of delocalised electrons’. The forces of attraction between oppositely charged particles is electrostatic. 15. B Circles of the same size and colour represent the same element. A compound is represented by 2 or more different circles combined together (touching each other). A: one compound B: a mixture of an element and a compound C: a mixture of two different elements D: an element 16. A Potassium oxide is an ionic compound. Ionic compounds are hard and brittle. 17. A Lithium bromide is an ionic compound. An ionic compound exists as a giant ionic crystal lattice structure. The 3D arrangement should consist of positive and negative ions held together by electrostatic forces of attraction. 18. B Each carbon atom is only bonded to 3 other carbon atoms, leaving one unb onded valence electron to be delocalised. Hence, there are delocalised electrons that can act as mobile charge carriers to conduct electricity. A: carbon ions are not formed C: wrong concept D: strong covalent bonds exist between carbon atoms 19. D The chemical formula consists of two units of CH3CNOH. Hence, in total, there are 4 carbon atoms, 8 hydrogen atoms, 2 nitrogen atoms and 2 oxygen atoms. So, in total, 16 atoms. 20. D From the formula Ir2(SO4)3, we can deduce that the ions are Ir3+ and SO42-. From the formula Zn(ClO)2, we can deduce that the ions are Zn2+ and ClO-. Therefore, the formula formed between Ir3+ and ClO- is Ir(ClO)3. 21. A B: the formula of magnesium chloride should be MgCl2 C: equation is not balanced. LHS has 2 NO3- groups but RHS only has 1. D: the formula of potassium sulfate should be K2SO4 22. C Electronic configuration of the ion of E = 2.8 (after gaining 3 electrons) Electronic configuration of the ion of G = 2.8 (after losing 2 electrons) So the ions are E3- and G2+. 23. C There are 3 Hg on the RHS of the equation. Hence, there should be 3 Hg on the LHS as well. Thus, w = 3 and y = 1. The values for w, x and y in option D will also work, but z is wrong as the number of H and O are not balanced.

GESS 3EXP CHEM EYE 2023 TKG 24. C percentage A 3(14) 27+3(14)+9(16) × 100 = 19.7% B 2(14) 3(24)+2(14) × 100 = 28% C 14 14+16 × 100 = 46.7% D 14 14+2(16) × 100 = 30.4% 25. C All the substances in this reaction are gases so we can use volume ratio directly instead of using mole ratio. 15 cm 3 of nitrogen (N 2) will react with 45 cm3 of hydrogen (H2). Since there is 60 cm3 of hydrogen, hydrogen is in excess, and nitrogen is the limiting reagent. After 45 cm3 of hydrogen has reacted with nitrogen, 15 cm3 of hydrogen is left. 30 cm3 of ammonia (NH3) was produced. Hence, the total volume of gas remaining in the container is 15 + 30 = 45 cm3. 26. B 68.54 100 × 63 + 29.51 100 × 65 + 1.95 100 × 67 = 63.6682 = 63.67 27. B carbon hydrogen mass 4.8 0.8 Ar 12 1 mass ÷ Ar 0.4 0.8 simplest ratio 0.4 0.4 = 1 0.8 0.4 = 2 ∴ empirical formula = CH2 28. A Na2CO3 + 2HCl → 2NaCl + CO2 + H2O no. of moles of CO2 = 3.0 ÷ 24 = 0.125 mol no. of moles of CO2 : Na2CO3 = 1 : 1 no. of moles of Na2CO3 = 0.125 mol

GESS 3EXP CHEM EYE 2023 TKG mass of Na2CO3 that reacted with HCl = 0.125 × 106 = 13.25 g percentage purity = 13.25 53 × 100 = 25% 29. C Amphoteric oxides that we have learnt are zinc oxide, aluminium oxide and lead(II) oxide. Metal oxides are basic while non-metal oxides are acidic. 30. A Calcium hydroxide is the chemical commonly used to neutralise acidity in soil, increasing the pH. Sodium hydroxide is an alka li that is too strong to be used. 31. D H+ ions are responsible for the acidic properties of acids. 32. D Since lead(II) sulfate is an insoluble salt, the precipitation method should be used. Hence, two aqueous solutions should be selected in preparing this salt. In option D, lead(II) nitrate and sodium sulfate are both soluble in water and can form aqueous solutions. In option A, lead metal and sulfuric acid will react, but an insoluble layer of lead(II) sulfate will be formed on the metal surface, hence stopping the reaction. This results in some lead metal not being able to react with sulfuric acid. In option B, lead(II) carbonate will react with sulfuric acid, but the same scenario in option A will happen too. In option C, both lead(II) chloride and barium sulfate are insoluble salts. Hence, when they are mixed together, both solids will not react with each other. 33. B In salt preparation, we usually want to obtain pure samples of the