BBSS Prelim P1 Ans

Bukit Batok Secondary School 1 Answers for 6092 Prelim Paper 1 (2024) S/N Ans Explanation 1 D 2 D Higher molecular mass and lower temperature, particles move slower. Hence, lower rate of diƯusion. 3 C At -190oC, nitrogen exists as a gas, hence weakest forces of attraction between particles. 4 B Y will distil first since it has a lower boiling point than Z. Y will float on Z, hence, Z will be collected first using separating funnel. 5 D The presence of zinc ions forms white ppt with aqueous ammonia and dissolves in excess to form a colourless solution. 6 D The two sub-atomic particles are electron (-1 charge) and neutron (0 charge). Hydrogen atom has one proton (one electron) but no neutron. Hydrogen atom gives away one electron to form hydrogen ion, hence, no electrons present in hydrogen ion. 7 D Evaporating the resulting solution is a physical change. Hence, statements from 1 to 3 are incorrect as there is no chemical change. Molecules of an element are formed because hydrogen is produced when magnesium reacts with hydrochloric acid. 8 B Hydrocarbons are covalent compounds. As relative molecular mass increases, the stronger the intermolecular forces of attraction between molecules. 9 C Graphite has delocalised electrons from the carbon atoms which will move along the layers of carbon atoms. Potassium chloride is an ionic compound, hence conduct electricity in aqueous state due to the presence of mobile ions. 10 D Graphene has similar structure as graphite, hence, similar properties. 11 A The number of moles of ammonia is the highest, 0.117 mol, compared to the other compounds. Hence, ammonia has the greatest number of molecules. 12 D number of moles of B2O3 = 2.50 g / 70 = 0.0357 mol number of moles of CO2 = 0.80 g / 44 = 0.01818 mol mol ratio of B2O3 to CO2 = 2: 1, hence, 4 boron atoms to 1 carbon atom, B4C 13 C When added to hydrochloric acid, carbon dioxide gas is produced. number of moles of CO2 = 0.6 / 24 = 0.025 mol mol ratio of CO2 to CaCO3 = 1 : 1, hence, 0.025 mol CaCO3 mass of CaCO3 = 0.025 x 100 g / mol = 2.5 g percentage purity = 2.5 / 3 x 100% = 83.3%

Bukit Batok Secondary School 2 S/N Ans Explanation 14 B number of moles produced in reaction 1 = 1.2 / 24 = 0.05 mol number of moles produced in reaction 2 = 4.0 / 40 = 0.10 mol number of moles produced in reaction 1 = 8.2 / 84 = 0.0976 mol 15 C As the elements are arranged in increasing proton number, W has the least number of valence electrons. Since all three elements are in period 3, all have three electron shells. Hence, statements 1 and 3 are correct. 16 B Going down group 17, the reactivity of halogen decreases. Chlorine being more reactive than bromine can displace bromine from its solution producing aqueous bromine (orange solution). 17 D Manganese is a transition element and form ions with variable oxidation states. 18 B This is a dilute solution of acid, hence, concentration of hydrogen ions should be lesser than w