JPJC 2026 H2 Chemistry WA1

2026 JC1 H2 Chemistry / WA1 1 © Jurong Pioneer Junior College JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 CHEMISTRY (9476) WEIGHTED ASSESSMENT 1 – For Practice Atomic Structure, The Mole Concept & Stoichiometry and Chemical Bonding Name : __________________________________ Raw score Class : 26S n Lack 3sf in final ans –1 / NA Date : _______________ Missing/wrong units in final ans –1 / NA Duration: 50 minutes Final score 25 INSTRUCTIONS TO CANDIDATES Answer ALL questions in the space provided. All numerical answers should be given to 3 significant figures, where appropriate. A Data Booklet is provided. 1 (a) Aluminium, Al, and gallium, Ga, are elements in Group 13. (i) Write the full electronic configuration of a Ga atom. 1s2 2s2 2p6………………………………………………… [1] (ii) Sketch a graph in Fig ure 1.1 to show the trend in the first seven ionisation energies of an Al atom. Figure 1.1 [1] 1st 2nd 3rd 4th 5th 6th 7th

2026 JC1 H2 Chemistry (9476) / WA1 2 © Jurong Pioneer Junior College (b) Table 1.1 shows the first ionisation energies for three elements, Mg, Al and Ga. Table 1.1 element Mg Al Ga first ionisation energy / kJ mol–1 736 577 577 (i) Explain why the first ionisation energy of Al is smaller in magnitude than that of Mg. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [1] (ii) Explain why the first ionisation energy of Al is the same as that of Ga. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] (c) (i) Deduce which ions, Al3+ or O2–, is larger. Explain your answer. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2]

2026 JC1 H2 Chemistry (9476) / WA1 3 © Jurong Pioneer Junior College (ii) When separate beams of 27Al3+ and 16O2– are passed through the same electric field, the particles are deflected to opposite directions. Given that the angle of deflection of 16O2– is 4.0°, calculate the angle of deflection of 27Al3+. [1] [Total: 8] 2 (a) Acidified potassium manganate( VII) is a common oxidising agent. It can oxidise ClO2– ions, C2O42– ions, Fe2+ ions, and many other reducing agents. (i) Construct a balanced ionic equation for the reaction between ClO2– ions and acidified MnO4– ions, given that ClO2– ions are oxidised to ClO3– ions. [1]

2026 JC1 H2 Chemistry (9476) / WA1 4 © Jurong Pioneer Junior College An impure sample of BaC 2O4 with a mass of 0.550 g is added to 50.0 cm 3 of 0.0200 mol dm–3 acidified MnO4–(aq), which is in excess. A redox reaction occurs in which all the C2O42– ions react completely to form CO2 gas. 5C2O42– + 2MnO4– + 16H+ → 10CO2 + 2Mn2+ + 8H2O The resulting solution, containing unreacted acidified MnO 4–, is then titrated with 0.0500 mol dm–3 Fe2+(aq). The following reaction occurs during this titration: MnO4– + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O 29.40 cm3 of 0.0500 mol dm–3 Fe2+(aq) is required to reach the end-point. (ii) Calculate the amount of MnO4– left after the reaction with BaC2O4. [1] (iii) Calculate the amount of MnO4– ions that reacted with all the C2O42– ions in the 0.550 g impure sample. [1] (iv) Hence, calculate the percentage by mass of BaC2O4 in the 0.550 g impure sample. [Mr of BaC2O4 = 225.3] [2]

2026 JC1 H2 Chemistry (9476) / WA1 5 © Jurong Pioneer Junior College (b) Sodium chlorate( I), NaC lO, is the active ingredient in commercial bleach. The concentration of chlorate(I) ions, ClO–(aq), can be determined by adding an excess of hydrogen peroxide to the sample of the bleach solution and measuring the volume of oxygen gas produced. H2O2(aq) + NaClO(aq) → NaCl(aq) + O2(g) + H2O(l) When an excess of aqueous hydrogen peroxide was added to a 5.0 cm3 of a bleach solution, 82 cm3 of oxygen was produced at room temperature and pressure. Calculate the concentration of ClO– ions in this bleach solution. [2] (c) 40 cm 3 of gaseous hydrocarbon, C xHy, was exploded with 200 cm 3 of excess oxygen. The mixture was completely burnt. The resultant gaseous mixture has a total volume of 140 cm 3. When these products were passed through aqueous sodium hydroxide, the volume decreased by 120 cm3. Given that all volumes were measured at room temperature and pressure, deduce the molecular formula of the hydrocarbon. [2] [Total: 9]

2026 JC1 H2 Chemistry (9476) / WA1 6 © Jurong Pioneer Junior College 3 (a) Hydrogen halides are covalent compounds with relatively low boiling points. Figure 3.1 shows the boiling points of HCl, HBr and HI. The boiling point of HF is not shown. Figure 3.1 (i) Explain why HI has a higher boiling point than HCl. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] (ii) On Figure 3.1, plot the boiling point of HF. Draw a labelled diagram to name and show the strongest intermolecular force present between two HF molecules. [2] Boiling point / K 300 280 260 240 220 200 180 160 140 HF HCl HBr HI x x x

2026 JC1 H2 Chemistry (9476) / WA1 7 © Jurong Pioneer Junior College (b) Silicon tetrafluoride, SiF4, sulfur dichloride, SCl2, and sulfuryl fluoride, SO2F2, are covalent compounds with similar relative molecular masses (Mᵣ). Table 3.1 shows their Mr and boiling points. Table 3.1 Compound Mr boiling point / C SO2F2 102.1 –55 SCl2 103.1 60 SiF4 104.1 –86 (i) Draw a ‘dot-and-cross’ diagram to show the bonding in a molecule of SO2F2, with S as the central atom. Include all outer shell electrons in your diagram. Predict the molecular shape of SO2F2. Shape of SO2F2 molecule: …………………………………………… [2] (ii) In terms of structure and bonding, explain why SCl2 has a higher boiling point than SiF4. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2] [Total: 8]