NYGH 2019-S3EOY-IP Chem P1 and P2 Ans

Secondary 3 (IP) EOY Answers 2019 Sec 3 End-of-Year Exam Chemistry Answers Paper 1 1 B 2 A 3 B 4 A 5 D 6 B 7 D 8 C 9 D 10 C 11 C 12 A 13 A 14 C 15 B 16 A 17 C 18 A / C 19 B 20 D 21 D 22 D 23 B 24 C 25 B 26 B 27 C 28 A 29 B 30 C Qn Ans Explanation 1 B Mixture of solid (ice) and liquid (water) will be at regions with constant temperature. Q-R is at a lower temperature so that would be the solid-liquid mixture. 2 A Neon has the lowest mass (20.2) compared to F2 (38.0), HCl (36.5) and SO2 (64.1). Hence, the one with the lowest mass will diffuse out of the balloon the fastest. 3 B The melting point of a pure substance would be lowered when impurities are added. The melting range for BOTH tin and lead (where both are liquids) would thus be from 80 to 220 °C. 4 A The drying agent is a basic oxide that can only dry alkaline or neutral gases. Acidic gases like carbon dioxide and chlorine cannot be dried using calcium oxide. Between ammonia and oxygen, ammonia (NH 3) has a molecular mass of 17 while oxygen (O2) is 32. Hence, ammonia, being less dense than air, can be collected by upward delivery method. 5 D In a school laboratory (i.e. at room temperature), substances X and Y are both liquids. Since they have different solubilities in water, they are considered immiscible liquids that need to be separated using a separating funnel. 6 B amino acid Rf value in solvent X Rf value in solvent Y Identity I 5.5/8=0.69 2/10=0.20 arginine II 3/8=0.38 3/10=0.30 glutamic acid III 4/8=0.50 8/10=0.80 cannot be identified 7 D Ozone makes up the ozone layer that cuts down on the harmful UV rays entering the Earth’s surface. Hence, it should not increase the chance of skin cancer. 8 C Combustion, flue gas desulfurisation and respiration all release carbon dioxide into the atmosphere. 9 D In acid, bromophenol blue is yellow and congo red is violet. Initial colours would be yellow and violet, giving D as the only option. 10 C As more copper(II) sulfate appears as crystals, the concentration of the solution decreases because there is less dissolved copper(II) sulfate in solution.

11 C HnX  nH+ + Xn- Let concentration of acid be 1 mol/dm3 and volume of acid be 2 dm3. no. of mol of acid = 2 mol Let concentration of alkali be 2 mol/dm3 and volume of alkali be 3 dm3. no. of mol of alkali = 6 mol Hence mole ratio of acid:alkali = 2:6 = 1:3 1 mole of acid requires 3 moles of OH - for complete neutralisation. Therefore, acid must be a tribasic acid and n=3. 12 A C6H5NH2 forms OH– when dissolved in water, showing that it is an alkaline. Hence, it should turn litmus paper blue and form a blue ppt with copper(II) sulfate due to the presence of hydroxide ions. It should also react with sulfuric acid to form the salt (C6H5NH3)2SO4. 13 A Presence of Al3+ ions forms white ppt in NaOH that is soluble in excess NaOH. Hence, a colourless solution would be obtained. Presence of SO4 2- ions forms a white ppt i