2024 Zhenghua Prelim MS

Paper 1 Multiple Choice 27 August 2024 1 hour Additional Materials: Multiple Choice Answer Sheet Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, Centre number and index number on the Answer Sheet in the spaces provided. There are forty questions on this paper. Answer all questions. For each question, there are four possible answers, A, B, C or D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. A copy of the Periodic Table is printed on page 18. The use of an approved scientific calculator is expected, where appropriate. Name of Setter: Ms Tan Li Er Natalie This document consists of 18 printed pages including this cover page. [Turn over ZHENGHUA SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS CHEMISTRY 6092/01 Candidate Name: _____________________________ Index No: _____ Class: _________

2 1 Aqueous sodium hydroxide is neutralised by dilute hydrochloric acid in a titration. 25.0 cm 3 of aqueous sodium hydroxide is measured into a conical flask using a ...1... and a few drops of methyl orange indicator is added to the solution. The dilute hydrochloric acid is added to the conical flask using a ...2... . The end-point is reached when the methyl orange indicator turns ...3... . Which words correctly complete blanks 1, 2 and 3? 1 2 3 A burette pipette red B burette pipette orange C pipette burette orange D pipette burette red 25.0 cm3 of sodium hydroxide is measured using a pipette. Note the precision of the value. Value would have been recorded to 2dp if the instrument was a burette. Sodium hydroxide was present in the conical flask originally. The addition of methyl orange indicator would have turned the solution yellow in colour due to the high pH. Upon the addition hydrochloric acid, sodium hydroxide is neutralized and the end point is reached when the last drop of hydrochloric acid causes the solution to change colour from yellow to orange permanently.

3 2 Chromatogram 1 shows the separation of coloured inks in mixture Q, using solvent A. Chromatogram 2 shows the separation using the same piece of paper in another solvent B after it has been rotated 90° anti-clockwise. chromatogram 1 chromatogram 2 first starting line How many different types of ink are present in mixture Q? A 3 B 4 C 6 D 7 4 spots were found after immersing the paper in both solvents. 3 An element, Z, has p protons and n neutrons in the nucleus of its atoms. Z reacts with oxygen to form a basic oxide. Which list gives the correct information about the ion of an isotope of Z? number of protons number of neutrons number of electrons A p n + 1 p + 1 B p n + 1 p ‒ 1 C p + 1 n p + 1 D p +1 n p ‒ 1 Isotopes have different number of neutrons but same number of protons. Z is likely a metal as it forms a basic oxide. Hence, it has the tendency to lose electrons to form an ion. rotate 90° anti-clockwise second starting line Q Q

4 4 A solution contains barium ions and sodium ions and one type of anion. What could the anion be? A chloride only B nitrate only C sulfate only D chloride or nitrate Barium sulfate is highly insoluble in water. A precipitate would have been observed if sulfate ion was present. 5 Solid P conducts electricity and has a high melting point. – likely a metal When solid P is warmed with excess dilute hydrochloric acid, it partially dissolves leaving behind a residue. – likely one component of P does not react with the acid What is P? A brass – made up of copper (no reaction with acid) and zinc (reacts with acid) B copper(II) oxide C graphite D iron

5 6 In a molecule of hydrogen cyanide, HCN, what is the total number of electrons present and how many of them are involved in bonding? total number of electrons number of electrons involved in bonding A 14 4 B 14 8 C 26 4 D 26 8 H: 1 e- and 1 valence e- , C: 6 e- and 4 valence e-, N: 7 e- and 5 valence e- Total number of e- = 1 + 6 + 7 = 14 Note: only valence e- might be involved in bonding. Total number of valence electrons shared = 2 + 6 = 8 e-

6 7 Nitrogen dioxide is a dark brown gas and is denser than air. A gas jar containing nitrogen dioxide is sealed with a glass plate and is then inverted on top of a gas jar containing air. The glass plate is removed. glass plate air nitrogen dioxide

7 Which row correctly describes the colours inside the gas jars after a long period of time? The gases are at room temperature and pressure. upper gas jar lower gas jar A brown brown B colourless dark brown C dark brown light brown D light brown dark brown Diffusion occurs. 8 Sodium is a grey solid. Chlorine is yellowish-green gas. When sodium is heated and mixed with chlorine, a reaction takes place and a white crystalline substance called sodium chloride is formed. Which statement about sodium chloride is correct? A It is a compound of sodium and chlorine. B It is a mixture of sodium and chlorine. C It is a new element. D It is an alloy of sodium and chlorine . – alloys are mixtures , not compounds 9 Which equation represents the ionic equation of the reaction between zinc and dilute hydrochloric acid?

8 A Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g) B Zn(s) + 2H+(aq) → Zn2+(aq) + 2H(aq) C Zn(s) + 2HCl(aq) → ZnCl2(s) + H2(g) D Zn(s) + 2HCl(aq) → Zn2+(aq) + 2Cl–(aq) + H2(g) Zn(s) + 2H+ + 2Cl–(aq) → Zn2+(aq) + 2Cl–(aq) + H2(g) Cancel out spectator ions on both sides of the equation. 10 The formula for hydrated copper(II) nitrate is Cu(NO3)2.xH2O. It contains 36.5% of water of crystallisation by mass. What is the value of x? A 4 B 5 C 6 D 7 Percentage by mass = mass of water / molar mass x 100 % 36.5 = (18x) / (64 + 2 x 14 + 16 x 3 x 2 + 18x) x 100 36.5 = 18x / (188 + 18x) x 100 188 + 18x = (18x) x 100 / 36.5 188 + 18x = 49.315x x = 6

9 11 An aqueous solution of hydrochloric acid has a concentration of 2.0 mol / dm3. Different volumes of the acid are added to different volumes of aqueous sodium hydroxide. NaOH + HCl → NaCl + H2O The maximum temperature of each mixture is measured. The graph shows the results. What is the concentration of the aqueous sodium hydroxide? A 0.67 mol/dm3 B 1.3 mol/dm3 C 1.5 mol/dm3 D 3.0 mol/dm3 As neutralization is an exothermic reaction, the maximum temperature would be the highest when exact amounts of both chemicals react with each other (i.e. at 30 cm3 of HCl and 20 cm3 of NaOH). Number of moles of HCl = 2 x 30 / 1000 = 0.06 mol Number of moles of NaOH = 0.06 mol Concentration of NaOH = 0.06 / (20 /1000) = 3 mol/ dm3 12 8 g of X2O3, an oxide of element X, contains 5.6 g of X. How many moles of X does 5.6 g